The Draft Survey procedures and calculation ascertained as the following series :
 Reading the draftmark of the ship, which consist of six (6) points of draftmarks, i.e.; Fore, Midship, and After at both sides of the ship,
 Sampling and testing the sea water or dock water density at the place where the vessel floats,
 Determining of deductible weights by measuring and sounding of ballast tanks, fuel oil, fresh water that existing onboard at the time of survey,
 Using Hydrostatic Table provided onboard to calculation.
Reading the Draftmark of the ship
Commonly, all ship are designed with draftmark for working with Draft Survey to determined their actual weight. The draftmark could be find at six (6) points on the below places:
 Forward Port Side (FP),
 Forward Starboard Side (FS),
 Midship Port Side (MP),
 Midship Starboard Side (MS),
 Aftward Port Side (AP),
 Aftward Starboard Side (AS),
View the Draftmark:
Use the small boat to go around the ship and get as near as possible to the draft mark for best viewing. The surveyor should be read all above marks clearly, because reading the draftmark is the first and most essential process. I am not saying that other processses is not essensial, but this process is hard to do and involves many rules of conduct to gain the correctness and accuracy of Draft Survey itself (I will post it later). The draftmark read is recorded on the surveyor notebook, do not try to remember it or write down in your palm hand. Its useless and unprofessional.
Sampling and testing the sea water or dock water density
After reading the draftmark, directly engage with the sampling of sea water or river water around the ship’s dock. Why? Because the ship draft will not be the same at different water densities (at the lower density means the ship more sink and at the higher density means the ship more float). Where as the water density is subject to changes which follow with water tide that carrying different water salinity and temperature on to the ship dock. The sea water density is indeed at density 1.025 and the fresh water at density 1.000. To determine the density of water, we need the instrument named Hydrometer or Density Meter. Inserted the Hygrometer on to the water sample on the Sampling Can or Tube, then we could check the scale pointed on the surface of the sampling water. Records the water dock density as survey data.
Determining of deductible weights by measuring and sounding
Deductible Weight could measure by sounding the tanks which used the Sounding Tape or gauging the tank level by visual inspection. Any deductible weight such as Ballast Water, Fresh Water, Fuel and Diesel Oil, and Bilges is notify to check. Records all in the survey book includes with the density for Ballast and Bilges, and for Oil complete it with density and temperature . The Fresh Water was at density 1.000.
View the Sounding Pipe:
Using Hydrostatic Table provided onboard to begin calculation,
I think all necessary data was completed, so we could do calculation. The calculation is uses Displacement Table or usually called Hydrostatic Table. This table is included all data that we need to complete the calculation.

Raw Draft Calculation; Fore Mean or Fm = (FP+FS)/2, Mid Mean or Mm = (MP+MS)/2, and Fore Mean or Am = (AP+AS)/2. while Apparent Trim or AT = Am – Fm. the Apparent Trim is the Trim that visually find.

Draftmark posision and correction to perpendicular. As the ship draftmark is not placed at the perpendicular, the Fore and After draft should be corrected with distance from the draftmark to perpendicular. The correction rules is: if the Trim by Stern, the Fore correction should be minus and After correction plus, and if the Trim by Head (stem), the Fore correction should be plus and After correction minus. The Midship correction is parallel with the fore correction with the same pattern. Some Hydrostatic table provided with these correction result. But if not the reference pattern is for Fore Correction or Fc = (Fd x AT) : LBM and After Correction or Ac = (Ad x AT) / LBM. Where Fd = Fore distance to perpendicular, Ad = After distance to perpendicular, and LBM = Length Between Mark or Length between Fore and After draftmarks or LBM = LBP – (Fd + Ad).

True Draft Calculation / Draft Corrected; Fore draft corrected or Fcd = Fm + Fc, Mid draft corrected or Mcd = Mm + Mc, and After draft corrected or Acd = Am + Ac.

True Trim or TT : Actual Ship Trim after draft corrected or TT = Acd – Fcd.

Fore and After Mean Draft or FAm = (Fcd + Acd)/2, Mean of Mean Draft or MM = (FAm + Mcd)/2, and Mean of Mean of Mean Draft or MMM or Quarter Mean = (MM + Mcd)/2.

The above calculation is similar with : MMM = {(Fcd x 1) + (Acd x 1) + (Mcd x 6)}/8.

Coresponding to the MMM or Quarter Mean result, the surveyor could check the value of needed parameters on Hysdrostatic table like; Displacement, TPC, LCF, and MTC. Records them accurately.

Get the Displacement or Disp.

First Trim Correction or FTc = (TT x LCF x TPC x 100) / LBP. Could be plus or minus depend on LCF.

Second Trim Correction STc = (TT x TT x MTC x 50) / LBP. The result always plus (+).

Displacement corrected by Trim or DispT = D – (FTc + STc).

Density Correction or Denc = DispT x {(Aden – 1.025) / 1.025}. where the Aden is Actual Density that surveyor has taken sampling and testing previously. The density correction commonly in minus (), due to the Actual Density is usually lower than 1.025 (fresh sea water). In case of at some port where the water salinity is high, the density correction could be plus (+).

And we have got the Displacement corrected by Density or DispDenc = DispT + Denc. (after corrected by density we will get the actual ship weight as per shown by Draft Survey)

Deductible Calculation. The same as draft, the deductible also need to corresponding to the table that named Tank Table / Tank Capacity Table. Refer to the sounding records that done before, the surveyor could be calculate the total deductbile existing onboard. Total Deductible or Deduct = Ballast Water + Fresh Water + Bilges + Fuel Oil + Diesel Oil, this total should be minus to the Displacement corected by Density.

The Net Displacement or NDisp = DispDenc – Deduct.

The Net Displacement is the actual ship weight after minus with deductible weight. For Unloading, to estimate the quantity of cargo onboard, the Net displacement should be minus with Light Ship and Constant.
I think difficult for the amateur writer like me to describe the complex narration of draft survey calculation, but to make it clear, the sample of Draft Survey Calculation will be post sooner or later.. :)
For video reference >> http://www.sevensurveyor.com/video/
Using draft survey software link http://www.sevensurveyor.com/software/surveysoftmarinesurveyorsoftware/
Regards,
Surveyors
June 1, 2016
Dear Ryan,
Could you give more detail question?
May 3, 2016
Good day Sir Please send me the formula of Draft correction error so that I have an idea to calculate! Thank you very much
March 24, 2016
Hi Gavrail,
You could check at this link http://www.marinewiki.org/index.php/Freeboard_calculation
March 23, 2016
Please can you tell me how to calculate actual freeboard amidships with known fwd draft,aft draft , density and the freeboard from deck line.for example f5.44 a5.64 density 1.025 and freebord from deck line 20061906 mm
thank you in advance
July 5, 2013
Dear Bijay,
Thanks for visiting.
The trim correction has already posted previously. please check here for all post in Draft survey category : http://www.sevensurveyor.com/category/draftsurvey/
Regards,
Surveyors
July 4, 2013
Dear Graham,
You could check this link http://www.fas.org/man/dod101/navy/docs/swos/dca/stg404.html.
Regards,
Surveyors
July 4, 2013
Dear Pnhkiran,
Thanks, check this video first
Regards,
Surveyors
July 4, 2013
Dear Tun,
Thanks.
as I know, just multiply the per MT fee of Survey with total BL or Weight (depends on agreement).
Example: Survey fee per MT at US$ 3, BL quantity at 5,000 MT.
Survey fee = 3 x 5,000 = US$ 15,000.
Regards,
Surveyors
July 4, 2013
Dear Zoheb,
Thanks please check here http://www.sevensurveyor.com/draftsurveybargeoverhangmethod/.
Regards,
Surveyors
July 4, 2013
Dear Surveyors,
I have a barge (overall length 165ft, beam 43.5ft, depth 12ft, design draft 8.4ft with a design deck load of 1, 830lbs/ftsq.) I want to place a box (length 102ft x 18ft wide @ 308,297lbs CG is in the center). What is the calculation to place this box on the barge so that it will trim to the stern?
many thanks,
Graham
July 4, 2013
Dear Graham,
Thanks, could you explain more? I don’t get the point.
Regards,
Surveyors
July 4, 2013
i want to learn the ship draft calculations. But i dont know hoe to read draft.
July 2, 2013
hi sir
how r u ? ur web side is very nice its help me to learn how to calculate draft survey but sir i am unable to understabd how does trim correction calculate please can u help me how should i calculate trim correction what is the formula………
July 2, 2013
hi sir
ur web side is very nice its help me to learn how to calculate draft survey but sir i am unable to understand how does trim correction calculate please can u help me how should i calculate trim correction what is the formula to calculate it ………
regards
Bijay
July 2, 2013
Dear Surveyor,
We would like to know,loading port B/L weight and discharg port outter weight difference,how they can charge survey fee base on B/L weight ( exp : 100 mt x (B/L) 3 us$ ) or outtur weight x 3 us$.Please reply to me.
Best regards,
Tun
June 30, 2013
how to calculate the weight to be loaded on forward of a barge to get a freeboard of 1m in forward? The barge specification is L=45.72m, B=15.24m, Depth moulded=3.05m. Please reply.
June 25, 2013
can you help me, is there a simple way to calculate how much a north sea barge will trim if I place a load on its centerline just aft of mid point?
May 20, 2013
Dear Gaon,
You are welcome..
Regards,
Surveyors
May 16, 2013
Thank you very much.
you save me! :^) Have a wonderful day!
from South Korea
Gaon
May 7, 2013
Dear Trond,
Thanks for Visiting. Please check my previous post http://www.sevensurveyor.com/draftsurveytheaccuracyandfactorseffecting/.
also check my previous comment:
Nitin, when all the requirements in the calculation of survey based on the Draft UN / ECE Code 1990 followed, the accuracy could be expected in the limit:
– For ship >10,000 DWT between 0.1 s / d 0.3%.
– For ship <10,000 DWT between 0.3 s / d 0.6%.
In fact the practice of this ideal condition can rarely be achieved minimum range within the limits 0.5% of the total weight.
When the technique is still less true implementation, the deviation can be achieved up to 1%.
Here the experience and skill of surveyor are involved.
Regards,
Surveyors
May 6, 2013
Dear Roger,
Thanks for visiting.
Regards,
Surveyors
May 6, 2013
Dear Andrian,
Please revert back to the question made by Ramaz, the above calculation was included the constant to Deductible and ETC.
The deductible is not fitted by vessel and change/transferable at anytime, such as bunker, ballast, loading/discharging equipment not ship own like bulldozers or shore grabs, and the massive peoples on board (stevedores) should be considered as well. The constant is not included on deductible.
Net Displacement is included light ship and constant. To know the constant, you should refer to several data of previous ship draft survey experience before loading (ship in light condition).
Regards,
Surveyors
May 6, 2013
Dear Gregorio,
Thank you, i don’t have the program you meant.
Regards,
Surveyors
May 6, 2013
Dear Godwin,
The trim correction divided by 2, i.e; 1st trim correction and 2nd trim correction.
1st trim correction : {(trim x TPC x LCF x 100) / LBP}. The 1st trim correction is to correct the draught midships to the true mean draught, at the centre of flotation. This correction is also known as the correction for layer or layer correction.
2nd trim correction : {(trim x Trim x MTC x 50) / LBP}. The 2nd trim correction is for the shift of the centre of flotation (LCF) which occurs as the vessel changes its trim. The position of the LCF, as specified in the hydrostatic particulars, is normally for the evenkeel condition.
Both above corrections purposed to make the vessel at doable calculated her correct displacement.
Regards,
Surveyors
May 6, 2013
Dear Michel,
Thank you for your comments.
1. No. The keel plate correction is done once against the reading draft.
2. You should use Extreme Draft and/or Draft below the keel.
Regards,
Surveyors
May 6, 2013
Dear Theo,
You could check with the surveyor association in your country or . Commonly the organization or association is held the course for surveyor like in my country.
Or check the Diploma Program for Long Distance Learning at http://www.iims.org.uk, where the draft survey is includes on it.
Regards,
Surveyors
May 6, 2013
Thanks Yuwono. Keep a good work.
Regards,
Surveyors
May 6, 2013
Thanks Sunil.
April 30, 2013
We are a ferroalloy plant in Norway, purchasing raw materials abroad, with shipments to our port. Tha cargoes are invoiced acc. to B/L, again baced upon Draft Survey. We need to know the uncertainty level of DS in %. Is this in any way available from the DS calculations, or is there a general way of describing this?
February 17, 2013
Thank it give a lot of help with me.
February 7, 2013
Hello Sir Surveyor ,
Dear Ramaz,
The calculation steps are correct.
the dispute is when you are using trim.
As the trim definition is different between aft draft and fore draft
or Trim = Aft draft – Fore Draft.
Trim by Stern should be plus.
Trim by Head should be minus.
In this case your vessel trim is by stern (+).
Please check this recalculate:
Displacement : 4,354.800
1st trim corr : 2.650
2nd trim corr : 0.182
Displ corr to trim : 4,352.332
Density corr : 0.000
Displ corr to density : 4,352.332
Deductible ballast etc : 141.000
Net displ : 4,211.332
Light Ship : 1,218.000
Cargo loaded : 2993.332
Regards,
Hello sir ,
I sew these steps of calculation and wanted to ask you , in the term Deductible ballast , except the ballast quantity , bunker ( f.oil , d. oil, l.oil ) what else is included ? What about the ship’s constant ? How do we know the ship’s constant before discharging ? Net displacement means the quantity of the cargo included light ship except ship’s constant . Please , am I wrong ?
Regards, Adrian
November 12, 2012
dear surveyor,
i have a programmable calculator casio fx880 p i want it to set a program especially for draft surveying if you have a copy for this, can you share it to me. thank you
October 13, 2012
give me an elementary detail on trim correcction
October 12, 2012
Very well informative, but I’ve suffering the following;
1)When I’ve determined the ‘double mean draught’ do I still need to make a ‘keel plate’ correction?
2)Nowadays in hydro table two kind of draugth tables are mentioned; moulded draugth (T) and draught below keel (TK). Can somebody explain the difference between those and which I’ve to use for finding the right figures as disp, tpc and lcf…
Many thanks in advance, regards.
Michel
October 11, 2012
Please where can i take a practical course in draft survey?
TA
October 11, 2012
i want to try asnwer the above,
we can use interpalate formula :
((2.46 – 2.45 ) :( 2.50 – 2.45 )) X (226.0 – 219.8 ) + 219.8
(0.01 : 0.05) X ( 6.2 ) + 219.8
(0.2) X ( 6.2 ) + 219.9
1.24 + 219.8
221.04
result of 2.46 is 221.04
September 30, 2012
Hi,
Your site/postings have been of immense help. I’m a cargo inspector, with 10years experience, and only now am I learning draft surveying through your site.Thank you.
August 29, 2012
Dear Sach,
Thanks. Commonly the scale displacement on hydrostatic table is made base on standard seawater density at 1.025. To convert it to the dock water displacement you need the following formula:
Displacement x dock water density / seawater density.
example:
displacement = 10,000
dock water density = 1.022
= 10,000 x 1.022 / 1.025
= 9,971
Regards,
Surveyors
August 18, 2012
in the draft survey, after finding rhe scale displacement, how do we convert to the dockwater displacement please
sach
August 16, 2012
Dear Kader Elkhounchali,
Trim is the different between aft draft and fore draft.
So, Trim = aft draft – fore draft.
Regards.
Surveyors
August 16, 2012
how to calculate trim
August 16, 2012
comment calculer le trim
August 15, 2012
Dear Liphuatgan,
Thank you for question. In my opinion the over quantity is normal.
For bulk cargo, there are two options to state the quantity on B/L:
1. shore scale or weight scale or conveyor scale weight data.
2. draft survey calculation data.
Based on experience, most of draft survey calculations resulted more cargo quantity if you compare to the shore scale.
For instance; if the shore scale shows 11,500 MT, the draft survey could show 11,512 MT.
Actually it should not happen, the both methods must be shown the same quantity (if all standards going well).
Others related info as many factors affecting the draft survey (please check http://www.sevensurveyor.com/draftsurveytheaccuracyandfactorseffecting/).
Regards,
Surveyors
August 15, 2012
Dear Onowu Prince,
Kindly find the below, previous comment:
————————————————————
Question:
Dear Sir,
I would like to know tank sounding calculation formular.
sounding 2.46 m and trim 3.578 correction is = 0
3.0m 3.578m 4.0m
2.45 219.8 216.8
2.46 – ??? –
2.50 226.0 223.0
So how to gat for value for 2.46 m ,trim 3.578m ???
Best regards,
Tun
————————————————————
Answer:
Dear Tun,
First, you could do separate the calculation (interpolation) to find the quantity at the trim and sounding easier. See the following steps how to find 2.46 at trim 3.578:
i. (3.578 – 3.000) : (4.000 – 3.000) = 0.578 : 1.000 = 0.578 = A
ii. (2.46 – 2.45) : (2.50 2.45) = 0.01 : 0.05 = 0.20 = B
iii. 2.45 = 219.8 – {(219.8 – 216.8) x A} = 218.066 = C
iv. 2.50 = 226.0 – {(226.0 – 223.0) x A} = 224.266 = D
v. 2.46 = C + {(D – C) x B}
If you do the right calculation the result should be 219.306.
————————————————————
Hope this could help you.
Regards,
Surveyors
August 15, 2012
Hi there
Would appreciate it very much if someone out there who could kindly comment on the following:
Is it normal that the weight of the bulk cargo (e.g. petcoke) after unloading from a barge calculated by the draft survey is always more than the amount stated in the Bill of Lading?
Thank you
August 6, 2012
i have problem in interpolating for ballast please explain i have clear and simple explanation
July 17, 2012
Thanks Ramaz.. GL
July 16, 2012
Dear Surveyor I calculate again and found different in my calculation,well understand.Thank you very much,God bless you and your family for help.
Brgds
Ramaz
July 16, 2012
Dear Ramaz,
The calculation steps are correct.
the dispute is when you are using trim.
As the trim definition is different between aft draft and fore draft
or Trim = Aft draft – Fore Draft.
Trim by Stern should be plus.
Trim by Head should be minus.
In this case your vessel trim is by stern (+).
Please check this recalculate:
Displacement : 4,354.800
1st trim corr : 2.650
2nd trim corr : 0.182
Displ corr to trim : 4,352.332
Density corr : 0.000
Displ corr to density : 4,352.332
Deductible ballast etc : 141.000
Net displ : 4,211.332
Light Ship : 1,218.000
Cargo loaded : 2993.332
Regards,
Surveyors
July 14, 2012
Good day. First of all thanks for reply me. I would like to check my calculated draft survey if you don’t mind which I have below.
If we know that :
LBP=105 LIGHT SHIP=1218 Density=1.025
Diesel45 mts , Oil18 mts;Lub oil 15;Fw21 mts;Other12 mts, Constanta:30 mts,
Step1: Find : M.
Frd(stb)=3,10 Frd(prt)=3,20
Mid(stb)=3.20 Mid(prt)=3,30
Aft(stb)=3.30 Aft(prt)=3,40
Found M for Frd;Mid;Aft;
Step2: Find: MM
MM for Frd= Frd(stb)+ Frd(prt)/2=3,10+3,20/2=3,15
MM for Mid= Mid (stb)+ Mid (prt)/2=3,20+3,30/2=3,25
MM for Aft= Aft(stb)+ Aft(prt)/2=3,30+3,40/2=3,35
Found MM.
Step3.Find Trim and MMM:
Trim=FrdAft=3,153,35= – 0.2 but,we must correct Trim and :
Trim x frd/LBP(frd+aft)= 0,2 x 3,15/105(3,15+3,35)=0,63/98,5=0,0063 ()
Trim x aft/LBP(frd+aft)= 0,2 x 3,35/105(3,15+3,35)=0,67/98,5=0,0068 (+)
Step4: 3,15(frd) 0,0063=3,1437 corrected draft for Frd
3,35(aft)+0,0068=3,3568 corrected draft for Aft
So corrected trim is corr, Frd – corr. Aft = 3,14373.3568 = 0.2131 from this we can calculate true MMM
MMM=frd+(mid x 6)+aft/8=3,1437+19,5+3.3568/8=3,250
Corrected MMM=3,250 and Trim 0.2131
From hydrostatic table for 3,25 draft:
Displacement = 4354,8
TPC = 14,34
LCF = 0.91
But for MTC must be found correction MTC=MMM(+ – 0.50)=MTC1 – MTC 2= corr.MTC
MTC1=108,39
MTC2=99,97
MTC1 – MTC 2=108,39 – 99,97 = 8,42
Corr.MTC = 8,42
Step5: Must be found 1st and 2nd correction
1st corr = 100 x tpc x lcf x trim / lbp = 100×14,34x(0,91)x(0,2131)/105=2,64840 about 2,648
2nd corr = trim x trim x mtc x 50 / lbp = 0.04541 x 8,42 x 50 / 105 = 0,18201 about 0,182
1st corr + 2nd corr = 2,83
Step6 : Displacement + 2,83 = 4354,8 + 2,83 =4357,63
Corrected Displacement is 4357,63
Finally Displacement light shipDieselOilLub oilFwOtherConstanta=lauded cargo
4357,63 – 1218 – 45 18 – 15 – 21 – 12 – 30 = 2998,63 mts.
Total cargo on board : 2998,63 mts.
If you found mistake please correct me and reply. Beforehand Thanks.
Brgds Ramaz
July 13, 2012
Dear Ramaz,
The second calculation is the correct one.
The formula is distance to pp x trim / LBM. Where the LBM is the lenght between aft distance to pp to fore distance to pp.
or LBM = LBP – (aft distance to pp + fore distance to pp).
Thanks you.
Surveyors
July 12, 2012
Good day. I have some question about DRAFT CORRECTIONS TO THE PERPENDICULARS. I have seen different calculation and can not understand in example 1.If we have FRD: 3,1 M and AFT: 3,4 M and Trim: 0,3 and LBP 105 M So DRAFT CORRECTIONS TO THE PERPENDICULARS for Frd: frd x trim/lbp 3,1×0,3/105=0,00885 and for Aft:aft x trim/lbp 3,4×0,3/105=0,00971 example 2.for Frd:Trim x Frd/Lbp(frd+aft)=0,3 x 3,1/1056,5=0,3 x 3,1/98.5=0.00944 and for aft:Trim x Aft/Lbp(frd+aft)=0,3 x 3,4/1056,5=0,3 x 3,4/98,5=0,01035 and we can see different between 1st and 2nd example and I would like to ask to you which one is correct or maybe is some different corrections ?
Beforehand Thank you for help.
Brgds Ramaz
July 10, 2012
Dear Venkatesh,
You could check some associations for marine surveyor, they usually doing training for survey and surveyor.
One of them you could visit http://iims.org.uk to get more info.
Regards,
Surveyors
June 23, 2012
I am working marine survey company since 10 years as a draft surveyor, i have experience in draft survey. But i want a certificate (licence) for survey. How can get the licence from III.
venkatesh
visakhapatnam
June 9, 2012
Dear Surveyor,
A full version of Draft Survey program was donated to Surveyors. It was forwarded via email on June 7, 2012. We have not received your confirmation if it was well received.
Best regards,
Capt. Michael
June 8, 2012
dear sir,
im a junior surveyor in malaysia. rcently im having some problem with this barge where i always loss about 30mt with F/W(SG:1.000). i already triple check my calculation in both initial and final survey onboard that ship. but still i cant figure where does this 30mt gone. is there any formula that i missed? i mean for ‘density correction’ i used (actden1.025xdisp/1.025). i did wrong or what? pls help me….
June 8, 2012
if were dealing with the fresh water, how to calculate. Any other formula? because every time i calculate this barge i always loss 30mt with F/W(SG:1.000)…
June 5, 2012
Dear Capt. Michael,
Thanks you.. Hope this software is useful for surveyor around here. If you wish you could send me the full version. So, I could test it and then write down the review post on my website.
Regards,
Surveyors
June 5, 2012
Dear Surveyor,
We are happy to announce that Draft Survey demo is now available for download from our website: http://www.mwmarineservices.com
We hope that you enjoy this software.
Capt. Michael
MW Marine Services, LLC
May 26, 2012
please, i would like you to give me a book on ballast sounding as well as metric conversion of values. Possibly, any page on bunker and ullage. In your thoughts on ballast sounding you did not expantiate on soundings that needed to be interpollated.. pls sir i would like you to shed light on that as well.
thanks
george
May 24, 2012
Dear sir,
what is trim correction and correction of deformation plz tell me completly if send mail more better for me
April 30, 2012
Dear Capt. Michael,
thanks for your advice.
As my experience, reading the mid draft mark is more easy and accurate than we do measuring / sounding the freeboard. the sea water swell and bad current disturbances are the most affecting factor of sounding / measuring the freeboard.
Regards,
Surveyors
April 26, 2012
Dear Captain,
Thank for your interest in my new Draft Survey program, which is backed by my longtime draft surveying experience. Presently, I am testing it and shortly I should have a Demo version on my website available for download. I will let you know when it’s ready for download.
You are doing a good job giving people very valuable advises regarding draft survey. However, I do not see anybody talking about taking a freeboard to obtain midship draft. As we know draft marks are not certified and the midship draft is the most important one in draft survey.
Best regards,
Capt. Michael
April 20, 2012
Dear Capt. Michael,
thanks for your valuable information.
hope you could give the trial version of software for the surveyor around here to test.
Regards,
Surveyors
April 18, 2012
Captain,
I have over 30 years experience in surveying including draft surveys. To help fellow seaman soon I will have a newly designed perfect Draft Survey program. Preview available now at http://www.mwmarineservices.com
Any comments or questions are very welcome.
Capt. Michael
April 16, 2012
Dear Ian,
suggested to use the following:
– Expect to read the Draft maximum sea vessels, although it is not possible or dangerous.
– In circumstances like this, read the Draft and land next to the sea with the help of manometer, consisting of clear plastic hose, strong, mounted on both ends of the pipe to facilitate water level measurements.
– If possible, pipes installed along the width of the entire ship – the size is taken from the overall width.
– Reading Draft sea side obtained through adding to or subtracting from the land side of the manometer readings
– The surface is measured from the same base line and taken to the same distance from both sides of the ship’s centerline.
– All air must be expelled from the hose and the pipe surface is maintained at a higher elevation than the deck on the centerline.
– The height of the water surface on both sides of the ship measured above deckline (h) or other fixed surface. The difference between the height divided by two and the result (d) is added to or subtracted from the readings Draft one to get the mean on Draft centerline.
SAMPLE OF CALCULATION
– QUESTION:
Draft midships left = 8.00M, the right side of the manometer readings 8.50M on both sides of centerline.
Full width of the ship = 20.85m. Draft midships Calculate the mean, the centerline Draft, if the difference between the 2 readings manometer manometer readings higher right = 25cm.
– ANSWER: The width of effective 8:50 x 2 = 17.00M, with the triangle at 0:25: 17 = d: 20.85
d = 20.85×0.25: 17 = 0.307m wide differences in management.
Differences halfwidth = 0307: 2 = 0.153m. Centerline Draft = 0153 8:00 = 8.153m
DRAUGHT SURVEY
THE U.K. VERSION, 1994
April 12, 2012
can you give me the formula for calculating the draft of a ship if :
i can only read the draft on the shore side;
considering the list at the time of reading draft;
i need to find the draft in the sea side:
e.g. actual draft reading on stbd side midship is 18.00m
a list on stbd side of 0.5 degress.
what will be the drafts on port side midship
ian carolino
April 8, 2012
i want to find the simplest way to calculate overall cargo of ship (coal , agri, liquid ) and also want planning for stocking of container in a vessel
February 19, 2012
for joseph, try this link for basic formula : http://webcache.googleusercontent.com/search?q=cache:aDpr1c9nngsJ:kaizad.co.uk/data/Cargo/Draught_survey_01.xls+rumus+draft+survey&cd=10&hl=id&ct=clnk&gl=id
sincerely yours
February 14, 2012
Dear Muhammad,
1st trim correction : (TT x TPC x LCF x 100) / LBP
2st trim correction : (TT x TT MTC x 50) / LBP
TT = true trim = trim after corrected to distance of perpendiculars.
Just try it now.
Regards,
Surveyors
February 14, 2012
Hi Nisay,
There are many ways to learn, you could find the one which suitable for you. For me, practice is the best teacher.
Regards,
Surveyors
February 14, 2012
Dear Marian,
Draft survey for all ship are use the same procedures and calculations.
Please refer to draft survey posts and donwload the available materials on this blog.
If you find any disputes, you could drop the comments.
Regards
Regards,
Surveyors
February 14, 2012
Dear Amit,
The 1st trim correction could be plus or minus. it’s depends on trim and LCF.
Regards,
Surveyors
February 8, 2012
Dear sir,
Here below is the dimension of the Hopper barge
LENGTH OVERALL : 32.5 MTS”
BREADTH : 7.3 mts”
DEPTH : 2.5 MTS”
G. R. T. : 182.33 TONS
NO. OF OPENINGS : 04
Please advice what would be the volume of the hopper barge,
the cubic capacity of loading the silt from the ocean bed.
Awaiting your reply ASAP.
Regards
February 1, 2012
Dear Faisal,
please guide me and post simple way to calculate Trim correction.
I’ve always making mistakes when do trim correction manually.
special with different type of vessel sounding tables.
Thank you so much.
May ALLAH bless you
January 20, 2012
dear sir
I AM DOCUMENTATION PERSON OUR OFFICE PEOPLE PUT ME AS A TRAINEE IN OPERATION SECTION.
I WANT ABOUT KNOW BERTHING DRAFT OF CAR CARRIER AND PROJECT SHIP
HOW TO CHECK THE DRAFT PLEASE TELL ME
REGARDS
SATHISH KUMAR
January 3, 2012
Hi, I’m a student and I have to do a final essay about draft measurement/reading installation on a containership, and the problem is that I can’t find any information on this installation. If you can help me with some information I would be very grateful. I expect your email. thank you very much
December 25, 2011
I’m a young surveyor,i realy want to be a proffesional in draft surveyor. Pls,is there any material to consult that will be a directive medium for me? I need your reply, thanks.
December 17, 2011
hello all
i am a surveyor for many years but never learned to take a draft
i want to learn it what is the best way????
thanks greets from holland
December 10, 2011
hallo,
sometime, in my job, i have to make delivery to the barges and all time i hyre to draft surveyors – much better on F 6 or F8.
pls i can get legal procedure for calculate the quant. on iland water ship draft survey?
tks and compliments
November 30, 2011
dear surveyors
pls tell me 1st trim correction sign
November 29, 2011
Dear Surveyor,
1 can u please let me known, how many meters are required for sampling water which are used for density.
2 where come from the water which are used for hose test.
thanks in advance for some explanation.
regards
Alberto Machenera
Beira , Mozambique
November 23, 2011
Dear Beny,
Thanks for your comments.
The draft survey calculation is applicable for the bulk barge as well. During my experience, the barge calculation is more simple than the ship. But the basic and reference are the same. In some barges, they dont have the midship draft, and foreaft distance to perpendiculars. It is easier to make calculation.
Regards,
Surveyors
November 23, 2011
Dear Mr Surveyors.
at first, thanks for your information about this posting its so helpful for me.
this calculation may applicate on draft coal bulk barge or there is have own calculated?
Regards
Beny
November 16, 2011
ASSALAM ALAEKUN MR FAISAL.I AM A STUDENT THAT IS NEW TO CARGO MARINE SURVEYOR AND I NEED YOUR HELP IN TERM RESEARCH SITE AND EBOOK PLS YOU CAN FORWARD THEM TO MY EMAIL THANKS
October 21, 2011
Can someone explain to me how do I find the:
1. Distance of forward marks from forward PP;
2. Distance of midship marks from midship;
3. Distance of aft marks from aft PP;
And most importing when we put the positive (+) and negative () sign.
October 4, 2011
Dear Giri,
Read it carefully, and discuss it with your surveyor friend.
Regards,
Surveyors
October 4, 2011
Hi Lars,
Very good question. If have time, I will try to post it soon.
Regards,
Surveyors
October 4, 2011
Dear Nielzkie,
In this blog there are some post about draft survey, you could check it for your references.
Regards,
Surveyors
September 8, 2011
I feel very happy to learn from this and also confused.If u dont m plz send me very important points
August 16, 2011
Srs,
Venho pedir – lhes mais esclarecimento sobre MTC e suas considerações.
August 13, 2011
may i knw hw to calculate barge dead weight, is it got formula?
August 11, 2011
can i do the short term course on DARFT Survey from Indian instute. If yes, from where ?
July 24, 2011
i need a draft measuring device for ship draft survey. from where i can purchase it.
please let me know.
July 18, 2011
kindly outline for me the most technical procedure of calculating the volume gas in a ship gas tank or static layed tank.
thanks for your expected response.
July 7, 2011
Dear Sir,
Good day to you…what are the formula on finding Draft survey..
Hope you can reply me with the formula’s
Ty…….so much…
July 1, 2011
Hi Sajjad,
You could check here http://v5.books.elsevier.com/bookscat/samples/9780750660006/9780750660006.PDF and http://mysite.du.edu/~jcalvert/tech/fluids/cargo.htm.
Regards,
Surveyors
June 14, 2011
Good afternoon Surveyors
Please advise where I can get formulas for calculating theoretical values of
1.Length between perpendiculars
2.Dipslacement based on dwt or GRT or NRT along with length, beam and draft
I need the formulaes for different types of vessels ranging from very small boats to VLCC. I need it for rubber fender design.
Kindly assist.
February 17, 2011
Hi Rahul,
Please make it specific, what is the formula you mean? what calculation do you wanna do?
Regards,
Surveyors
February 16, 2011
Dear Ferdhy,
First way:
– You have to read 12 (twelve) times when the swell showing the high and the low levels.
– From the above reading you have to eliminate 2 readings (1 of the highest level and 1 of the lowest level)
– Take 10 readings which you have to then make an average by divided to 10.
– The result gained is the best draft that near to the actual draft.
Second way
It is recommended to use the Draft Measuring Equipment. A measuring device may to be use to improve the accuracy of draft measurement. Such device are based on the principle that the turbulence on the surface of the water does not extend down to any great depth. they use a long, flexible, open ended, weighted hose projecting downwards to below the turbulence.
Regards,
Surveyors
February 9, 2011
what is the formula for cargo calculation
January 26, 2011
Dear mr. surveyor
how to read actual draft mark at water swell condition,thanks
January 22, 2011
Dear Anatoly,
I have no formula that you meant.
The trim factor is made for trim correction at Forward, Mid, and Aft. These correction applied at the mean draft to obtain the corrected mean draft.
Regards,
Surveyors
January 22, 2011
Dear Anatoly,
I have no formula that you meant.
The trim factor is made for trim correction at Forward, Mid, and Aft. These correction applied at the mean draft to obtain the corrected mean draft.
Regards,
Surveyors
January 22, 2011
Captaouf,
Yes you could do it. The Draft Survey is possible for any conditions you meant.
Regards,
Surveyors
January 22, 2011
Hi George,
Thanks for your questions. As long as I know, the ship tank table is made calibrate with the trim (apparent trim). So, we have to refer to these trim.
In the other hand, if you find any information from the ship that the table is made refer to actual trim, you should use the actual one.
Please remind me if any issues regards this.
Regards,
Surveyors
January 5, 2011
Good Day,
Sometimes there is no LCF mentioned in ship’s hydrostatic tables, but there are “trim factor fwd” and “trim factor aft”. There is a formula to get LCF using both trim factors and LBP. Mr. Surveyor, do you have the formula?
Thanks for help.
Anatoly.
December 15, 2010
it possible the calculate the draft survey with negative trim or even keel
December 12, 2010
Dear Surveyors!
Have one question.
When we calculate the draft survey we use corrected trim (after correcting for distances of draft marks from perpendiculars) to enter the hydrostatic tables and ballast tables. So it used corrected trim to look at ballast tables with trim corrections.
However when everybody calculates the bunkers in fuel oil tanks or mdo tanks at time of bunker survey everybody use simply d.aftd.frw so called apparent trim. I mean that all chief engineers and surveyors I have seen so far use apparent trim to enter the capacity tables with trim for bunker tanks.
Why it so and is it a correct way?
Will be appreciated to hear any comments.
Bat rgds
George
December 8, 2010
Dear Ipah,
Thanks for comment. You may check the following links :
– http://www.riam.kyushuu.ac.jp/ship/ittc/presentation/ProcPropulsion.pdf
– http://www.martv.com/TECHPAPERS/All%20Papers/NavalArch/AnalysisA.pdf
Hope the above can help you.
Regards,
Surveyors
December 8, 2010
Dear Traore,
Ballast calculation is simple, you could obtain by the following steps:
– sounding the tank,
– taken the ballast water density,
– check the cubic quantity on the ship ballast tank table,
– and calculate the Metric Ton quantity.
For example :
– Sounding of tank DBT 1 P : 5.35 M,
– Ballast Water Density : 1.020,
– Cubic quantity on table at 5.35 M = 368.120 Cubic Meters,
– Metric Ton quantity = 368.120 x 1.020 = 375.482.
Best Regards,
Surveyors
December 8, 2010
Dear Nitin,
You could refer to the Loading Manual Book that provided onboard the vessel.
Regards,
Surveyors
December 5, 2010
dear captian, could you please send me the procedure and methods of surveying one unit of the propulsion plant of a ship. i am a cadet of maritime academy of Nigeria.
November 23, 2010
thank you for draft survey explanation.
can you explain us how to make calculation on ballast?
best regards
November 22, 2010
Dear Sir,
For bulker vessels ,could you pls. indicate any thumb rule OR
Empirical formulae,that based on draft,how can we ascertain
the cargo weight which can be loaded in the vessel.The range may
be taken from Cargo load of 7000 MT up to 15000 MT.
November 5, 2010
You are welcome Nguyenvanluu.
November 4, 2010
I see this brief very useful to me to figure out steps to calculate the draft survey.Thanks!
November 2, 2010
Dear Mcdudz,
The Draft Survey formula has considered to deflection correction, due to it was made up to the Quartermean (Mean of Mean of Mean – MMM), meanwhile the deflection correction is applied at the Mean Draft. The calculation result is the same for both methods.
Example (briefly, the calculation is directly to corrected draft):
Fcd = 2.232
Acd = 2.851
Mcd = 2.502
FAm = 2.542
1. For Draft Survey Formula :
– MM = (FAm + Mcd) / 2 = 2.522
– MMM = (MM + Mcd) / 2 = 2.512 (use to check corresponding displacement at table)
2. For Deflection correction:
– FAm = 2.542
– Hogging = 2.502 – 2.542 = 0.040 (Deflection or D)
– Equivalent Draft = FAm + 3/4 D = 2.542 + (3/4 x 0.040) = 2.542 + (0.030) = 2.512
For any abbreviations, you could refer to my late posts. Please advice me whether any mistakes.
Regards,
Surveyors
November 2, 2010
Dear Santoso,
Thanks, there no simple formula for Draft Survey. The Formula that I have inserted on my previous posts, as commonly use on the Ship’s Draft Survey.
Regards,
Surveyors
October 26, 2010
Dear sir,
I have respect for you explain any proble darft survey.
Can you give me a simple formula to calculate cargo on boat with draft survey?
Thanks for your answer.
Regards.
Practicips
October 12, 2010
Good day, I have some queries also, pls advise if the deflection correction are still aplicable now a days? As I look some draft survey reports, programs, the deflection correction is not found or applied. As you know in big ship’s specially more than 80,000 dwt, the deflection correction is big. Pls advise also your calculation in deflection correction if you have.
October 4, 2010
Dear Khan,
You can drop your question, comment or feedback on this website, due to I am rarely check my mail. My mail address is faisal.yusuf(at)live.com.
Regards,
Surveyors
October 2, 2010
Dear Sir
What is your email address? I tried to post my questions 3 times but seem like it go no where. Thanks.
Regards
September 10, 2010
Hi Luis,
I have ever found the same case like yours. The best you can do is find the terms on Hydrostatic Table that you working with. Usually in the first page you will find it.
When the first time meeting with this case, I am very confusing. I try to guess the LCF, and reopen the Hydostactic Table many times but nil. Then.. I asked the Chief Officer about it. Unfortunately he did not know because he is the new Chief Officer and doing calculate with the Loading Manual on Ship’s Computer. Or he wanna test the surveyor at the time :)
In the end, I reopened the data page and rechecked the Terms :
LBP = Length between Perpendicular
MTC = Moment to ChangeTrim at 1 cm.
etc.. etc. then I found
LCA = LCF (Longitudinal Center of Floatation)
That the answer.. So, I back to the table and checked the LCA and written down as LCF.
In the case, you may also find LCB = LCF.
It is recommended for surveyor to check the terms and the calculation rules that provided on the Hydrostatic Table prior doing calculate. If you are in doubt, please asking for the Original Hydrostatic (in blue printing) from the ship to get the correct information and calculation.
Regards,
Surveyors
August 16, 2010
Dear Sir.
In some vessels I have found that no information about LCF is vailable in the Hydrostatic tables, all the others are except LCF. Unfortunately no cross curves were available, no more ship’s info available also
There is some way to calculate the LCF value??
Appreciatte in advance your answer.
Luis
July 28, 2010
Dear Surveyor can u pl mail me what is the procedure to calculate draft of Petroleum Tanker / vessel and oil tanker / vessel
July 7, 2010
Hi Tamim,
Terimakasih untuk komentarnya..
Mungkin kamu belum begitu familiar dengan istilah perkapalan. Atau kalau bahasa yang menjadi kendala, kamu bisa kopi artikel nya dan terjemahkan di http://translate.google.com/#.
Ada juga Training Draft Survey yang diadakan oleh Asosiasi Independent Surveyor Indonesia (AISI) coba check di http://www.aisiindonesia.org.
Salam,
Surveyors
July 7, 2010
Hi Feras,
Please clarify what does “the vessel is half loaded but yet above zero” means? So, I could try to find the answer. Thanks.
Best Regards,
Surveyors
July 5, 2010
dir pak surveyor,
terima kasih atas artikel bapak ini, saya tertarik ingin mempelajari draught survey
tapi, saya bingung untuk mempelajarinya, karena ada istilah yang tidak saya mengerti dan perhitungannya
saya harap bpk mw memberi penjelasan tentang draught survey, istilah yang sering d gunakan dan contoh perhitungannya
July 4, 2010
dear sir,
my question is: regarding the lcf sign as to be applied for the formula used to calculate the first trim correction. what sign does the LCF get if it is reducing.i.e the vessel is half loaded but yet above zero!? is it minus or plus???
very urgent reply required
May 30, 2010
Waalaikum Salam..
Me in my best, thanks.
Draft Mark reading is the essential part of Draft Survey, where the Draft Survey is begin from the reading part. There are some rules to get the best result. Actually it should be write down in one posting, but the basics are :
– Read the Draft Marks as close as possible,
– Use the small boat to read close the Draft Marks, do not see it from the ship’s maindeck,
– Vessel is secured at the wharf properly,
– No any ship’s gears movement allowed at the time, (such as crane, derrick etc),
– No any ship’s liquids transfer activity allowed during reading, (ballast, fresh water, fuel and diesel oil),
– Find the draft in meter first then continue with centimeter to prevent big error.
– For the heavy swell sea condition it is recommended to read and record 12 times, taken out 1 biggest and 1 smallest of the reading results, and make avarage draft from the 10 results remained.
Trying to post this as complete version soon.
Second one, you could check my last post Draft Survey : Terms of Conduct for Light Ship and Constant Terms.
Regards,
Surveyors
May 30, 2010
Dear Joe,
Fisrt, the Density Correction is the correction for water mass weight. Commonly, the Ship Hydrostatic Table is makes at Sea Water Density (1.025). As the ship is floating on the sea water or river water that may have different densities, it shoud be applied density correction to gain the actual weight.
There is no relation between Density Correction to Ship Light Ship and Constant.
Regards,
Surveyors
May 27, 2010
Dir Sirs,
I’m new in this field of surveying and I was hoping if you could clarify the following;
Displ Corrected for trim – Actual Displ = Density correction.
Q: What’s the significance of ‘density correction’ and also is there a relation between Density Correction and the Ships lightship constant.Would greatly appreciate your expect advice and answers.
Kind Regards
Joe TOVA
May 26, 2010
Assalamoalykom
Dear Faisel
how r u, I read your data related to draft survey which is very helpful for me and i learn manay thinks which I not know abt. I am First time asking to you some questions my 1st question is that plz can you Expalan that which kind of Ruls are involved to Record Draft Marks (You said abt that you will post later) and my 2nd question is What is light ship & Constent onboard. please if you can send me answer by mail i will very thankfull of you
Best Regard Ejaz Khan
May 10, 2010
Good day. I am a junior surveyor struggling to learn draft survey
I would like to know the formula to calculate especially
LBM: length between mark
FD “ Fore distance to perpendicular:
AD : after distance to perpendicular:
Thank you very much indeed
May 2, 2010
Dear Sir
How do i calculate approx. draft of a newly build vessel with all deadweight on board.
What all parameters do i need for it from stability booklet.
Can you explain with an example.
April 2, 2010
DEAR SIR,
HIGLY APPRECIATE IF YOU SEND ME BY RETURN MAIL THE ASTM TABLE 54 FOR VCF DENSITY& TEMP CORRECTION
TKS& RGDS
March 18, 2010
Hi Mehdi,
Thanks for comment. Appreciated you as my Senior, as I have just completed 10% surveys of yours.
I think the data to be followed was written on the Hydrostatic Table. But if then we verify and will find that the both correction is applied trim to complete the calculation. The more trim you get the more correction will be.
FTc is more fluctuate than STc. Its happen due to point of LCF sometimes moving to the aft and fore of Ship Centre / Midship, where it will result the LCF in Minus and Plus. The value of LCF could be down below the 1.00 like 0.15 depends on the LCF’s distance from Midship. Mathematically, you have been times 0.15 with other numbers, but certainly you do devide it. This will be influent to reduce FTc total value when you do calculate it.
On the other hands, the MTC is not subject to minus. And the MTC value is typically the high number, means above 3.00, so it will advance for your calculation.
Anyone has any advice? waiting for your comment.
Regards,
Faisal
March 18, 2010
Nitin, when all the requirements in the calculation of survey based on the Draft UN / ECE Code 1990 followed, the accuracy could be expected in the limit:
– For ship >10,000 DWT between 0.1 s / d 0.3%.
– For ship <10,000 DWT between 0.3 s / d 0.6%.
In fact the practice of this ideal condition can rarely be achieved minimum range within the limits 0.5% of the total weight.
When the technique is still less true implementation, the deviation can be achieved up to 1%.
Here the experience and skill of surveyor are involved.
Regards,
Faisal
March 18, 2010
Dear Nitin,
Thanks, the Specimen of Calculation on the post is made for initial survey, when the ship arrive at discharge port. In the next steps, the surveyor need to carry out the final draft survey in the same way when the ship has completed discharge her cargo.
The initial survey Net displacement that deducting / minus with the final survey Net Dispalcement will show you the total amount of cargo discharge from the mentioned ship.
Regards,
Faisal
March 17, 2010
Dear Sir,
Could you throw some light on tolerance limits of Draft survey for different
vessel sizes.
March 17, 2010
PLs. explain me the total draft survey of a dry bulk vessel with detailed calculations .Pls. use one illustrative example and make use of figures,
March 3, 2010
Hi Nick,
Thanks, as known the correction is applied from the draft mark location. You could refer it to the Fore and Aft Distance on Hydrostatic Table that provided by the ship and compare with your draft reading place.
As my experience, the draft at the Aft on the flat of stern that usually found in the container ship is additional draft for reference only. You should check the port and starboard draft at stern for your draft survey.
Regards,
Faisal
March 3, 2010
Hi Herah..
Thanks for your questions.
Refer to your first question, I will post soon: how to calculate ship bunker.
The second: For SG 0.9900 is included on 0.8595 to 0.9245 with Correction Factor Per Degree Celcius at 0.00065.
Regards.
Faisal
February 28, 2010
Pls advise if the draft marks aft are on the flat of the stern and on the after end of the rudder need any correction or not. I see many containerships with the draft marks aft on the flat of the stern.
February 26, 2010
Hi Darussalam,
Thanks for your comment. Simplify the calculation for tank sounding were as follows :
– Sounding resulting Quantity in Cubic Meter (see on Tank Quantity Table).
– Quantity in Cubic Meter (x) Volume Correction Factor (from ASTM Table 54B) resulting Quantity in Kiloliter @15C.
– Quantity in Kiloliter @15C (x) Weight Correction Factor (from ASTM Table 56) resulting Quantity in Metric Ton.
– ASTM Table 54B for VCF is gained by Oils Density @15C and Temperature.
– The complete calculation will be posting soon. Just check the blog later.
Regards..
February 25, 2010
Sir,
what is the coefficient factor if you have 0.9900 Specific gravity @ 15 degree celcius?
February 25, 2010
Sir, plz answer this problem for calculating bunker:
A vessel is to take a 1000 MT of IFO.Calculate correction made:SG at 15 degree celcius is 0.9900: TCF at 40 degree celcius is 0.9844:average combined SG+TCF is 0.9700.
Can you answer this problem ?
February 25, 2010
Dear colleuges I have done almost 3000 attendances on vessels for draft survey..one thing which I still am thinking about and not found answer is in some cases the second trim correction was larger than FTC ..? Why
warm regrads
mehdi
February 25, 2010
dear sir,
thanks for the information… can you give me a simple calculation for tank sounding for bunker??
Regards Darus,
February 25, 2010
Dear Ariz,
Thanks for comments. The above formula you have submitted is not correct. You’d better to check it, maybe you misplace the elements.
Regards,
Faisal
February 25, 2010
Let ROB = x
A – B / C – B = x – D / E D
(AB/CB)+D = x / (ED)
(AB/CB)+D
____________ = x
(ED)
February 25, 2010
is there any shortcut for the interpolation method shown above? I know my professor taught us but coudn’t remember.
thanks
Aris
February 6, 2010
Thanks Pandya,
You could check in my previous post and read the downloadable materials..
February 5, 2010
Hello, Sir,
I am also surveyor too, i want to know what is the MCTC and way they uses during draft calculation LCF and MCTC, kindly give me reply,
thanks,
February 4, 2010
Dear Ashveer,
Thanks for comment. Please take a look the sample of Interpolation on my post Draft Survey: Specimen of Calculation.
I think there is no formula or easy method likes you meant. Because we should consider the unique shape of the ship to make calculation for Draft Survey (except for box shape vessel).
January 23, 2010
Good day. I am a junior surveyor struggling to learn interpolation . Is there a formula or do you have an easy method for calculating the weight using the true trim that is not on the hydrostatic table eg. T1 given t3 given calculate weight found t2 between given trims for a specific sounding. Really would appreciate your help
January 2, 2010
Thanks for the blogpost!
December 9, 2009
I use this correction formula for ballast tanks:
A=STrim*Ltank/(2*LBP)
A – Adjusted Sounding at Aft Bulkhead Tank
S – Actual Sounding
Ltank – length of the tank
Trim – vessel’s trim(+ to aft, – to fore)
LBP – length between perpendiculars
So after getting A, refers it to the Tank Capacity Table to find the quantity on Tank.
This formula can be used only when the tanks have a almost paralelipipedic shape (no way to be used for forepeak and afterpeak).
If the vessel has no correction tables for ballast tanks is advisable to ask that the vessel to be put on even keel(if is safe).
Mr. “surveyors”
Your formula show more ballast water in tank when vessel’s trim is to aft, which is not true.
October 29, 2009
Dear Sir,
i was wondering if you could post any example of procedure in draft survey on calculating the ballast considering trim and when ballast in cargo hold corrections for add. height when measuring from top. Also procedure when calculating fuel.
Regards,
student
October 28, 2009
Thanks Suhendar,
The Draft Survey and Shore Scale / Weight Scale were the same function to determine quantity of cargo. as long as I known there is no rules to arrange the percentage of differences for both techniques. Caused each Technique should be accurate. Draft Survey is depends on the Hydrostatic Table calibration, and the Scale is depends on the accuracy of calibration of unit of Scale.
Both of them are recommended. And if the Techniques has the same accuracy, it should be resulted the same figure of weight quantity. For Bulk Cargo, it is recommended to use draft survey, because you never know how much cargo losses or spillages during discharging and conveying by truck to the Scale. The Scale is essensially uses for actual quantity received by the Receiver.
For other readers, please submit your comments if you have got the rules as Suhendar asked for.
Regards,
Faisal
October 23, 2009
Dear All,
Kindly pls advise the rule for percentage of different between draft survey with shore scale/weigher.
Thanks/Suhendar
October 14, 2009
Alex,
You have to consider the trim of tug boat to obtain the correction of sounding that you have done, due to on tug / vessel with trim the liquid on tank were at different level between sides (fore and aft sides of tank). The correction is made to flat it on the same level (being actual liquid level) for calculation.
As your sounding quantity still in Cubic Meter, the density of fuel oil is needed to converted the Cubic Meter to Kilo Liter, and than from Kilo Liter to Metric Ton. ASTM Table 54b (for Volume Correction Factor or VCF) and Table 56 (for Weight Correction Factor or WCF).
Regards,
Faisal
October 13, 2009
Dear Sir,
What if we have to consider the trim of the tugboat and the density of the fuel oil?
Please advise.
Regards,
Alex
October 13, 2009
Thanks, that was really helpful.
October 8, 2009
Dear Capt. Valter,
Thanks to comment.
Although in calculation the differences of both methods (1 and 2) in small quantities as well, but it could be a question to standard of draft survey that we have to use from the our customers.
I am in opinion that the Displacement corrected to density should be the displacement after corrected by the 1st and 2nd trim correction. By mean, the vessel displacement should be free from all vessels unbox shape and uneven keel correction before correcting by density. This method is commonly use for bulk carrier and it recorded on vessel hydrostatic table.
The UN ECE might be mean the same, the D they meant is D after 1st and 2nd trim correction, where we mentioned as DispT.
Waiting for your next comments. :)
Best Regards,
Faisal
October 7, 2009
Dear sir,
I have find discrepancy between your way to calculate density correction and UN ECE recomandations (which is used as a standard for many customers). I’m asking You for the opinion becouse we have discousssed a lot among my coleagues.
The difference is in Displacement where by you Displacement corrected for the trim should be used, while by UN ECE standard the displacement from the table (line 161) should be used.
1. Your way and also my opinion is the same
Denc = DispT x {(Aden – 1.025) / 1.025}
2. UN ECE method
Denc = D x {(Aden – 1.025) / 1.025}
Please tell me your opinion.
Regards
Capt Valter Suban, M.Sc.
October 3, 2009
Thanks that was helpful.
October 3, 2009
Hi Milind,
– Expect to read the Draft maximum sea vessels, although it is not possible or dangerous.
– In circumstances like this, read the Draft and land next to the sea with the help of manometer, consisting of clear plastic hose, strong, mounted on both ends of the pipe to facilitate water level measurements.
– If possible, pipes installed along the width of the entire ship – the size is taken from the overall width.
– Reading Draft sea side obtained through adding to or subtracting from the land side of the manometer readings
– The surface is measured from the same base line and taken to the same distance from both sides of the ship’s centerline.
– All air must be expelled from the hose and the pipe surface is maintained at a higher elevation than the deck on the centerline.
– The height of the water surface on both sides of the ship measured above deckline (h) or other fixed surface. The difference between the height divided by two and the result (d) is added to or subtracted from the readings Draft one to get the mean on Draft centerline.
SAMPLE OF CALCULATION
– QUESTION:
Draft midships left = 8.00M, the right side of the manometer readings 8.50M on both sides of centerline.
Full width of the ship = 20.85m. Draft midships Calculate the mean, the centerline Draft, if the difference between the 2 readings manometer manometer readings higher right = 25cm.
– ANSWER: The width of effective 8:50 x 2 = 17.00M, with the triangle at 0:25: 17 = d: 20.85
d = 20.85×0.25: 17 = 0.307m wide differences in management.
Differences halfwidth = 0307: 2 = 0.153m. Centerline Draft = 0153 8:00 = 8.153m
DRAUGHT SURVEY
THE U.K. VERSION, 1994
October 3, 2009
Hi Alex,
Thanks, you have to use interpolation to get the mentioned quantity.
Let’s assume 2.380 = A, 2.375 = B, 2.400 = C, 26.15 = D, and 26.50 = E.
The Formula is: ROB = D + {((A – B) / (C – B)) x (E – D)}
As per the above formula the ROB found 26.157 m3. You can try it. :)
September 24, 2009
Dear Sir,
I would like to know the formula to calculate the remaining bunker (MGO/Fresh Water/LO/GO/DO) on board based on the tank sounding table.
For example:
Sounding – 2.38m
Tank sounding table shows:
1) 2.375 – 26.15m3
2) 2.40 – 26.50m3
How to get the value (ROB) at 2.38m?
Regards,
Alex
September 23, 2009
Can some one please guide me on the procedure of calculating overside drafts of a vessel with a list and where over side drafts cannot be successfully read.
September 8, 2009
Hi Myo..
Thanks for your comments.
As I know, there is no differences for formula between the Ship and Hopper Barge Draft Survey. Draft Survey formula is for general uses.
For references, you could download the complete Draft Survey Standard and Procedures at this LINK
September 6, 2009
Dear Sr,
Your posted were support me to learn about Draft survey.I’m a junior surveyor in our country,Union of Myanmar at South East Asia.
I want to request you that to explain about Draft survey for Barge carrier and Hopper calculation.Because the technique in our country were very poor to learn.I want to know the formula to calculate the water content of Sea Sand cargo.
Regard,
Myo
September 6, 2009
Hi James, thanks for your question..
I have made try to adopt from Petroleum Calculation named Weight Formula. The formula is as follows:
A = S + {(U – DF) x F}
Where :
– A : Adjusted Sounding at Aft Bulkhead Tank
– S : Actual Sounding
– U : Sounding point distance to Aft Bulkhead
– D : Total Height of Tank
– F : Trim Factor, where the formula is Trim divided by LBP.
– DF = D x F.
So after getting A, refers it to the Tank Capacity Table to find the quantity on Tank.
For example No. 2 Water Ballast Tank Portside:
Sounding = 1.27 meters,
U = 3.00 meters,
D = 19.00 meters,
Trim = 2.50 meters,
LBP = 182.00 meters
So we can calculate,
F = 2.5 : 182 = 0.014 and
DF = 19.00 x 0.014 = 0.261
Then,
A = 1.27 + {(2.5 – 0.261) x 0.014}
A = 1.27 + (2.239 x 0.014)
A = 1.27 + 0.031
A = 1.301. (check on Tank Capacity Table).
Does anyone has the other correction ways? I would be plesant if you could submit reply to this comment.
September 3, 2009
I found your brief on draught surveys very informative. Can you advise if there is a standard correction formula for asertaining the amount of ballast in a tank where there are no trim corrections available.
Regards,
James Barr