# Least Square Method (linear) - Freeboards and drafts

Discussion in 'Education' started by Transom6.3, Sep 22, 2009.

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### Transom6.3New Member

Hi Guys,

I have seen the least square method (linear) in a number of inclining test reports when used to get the inclined waterline from a number of freeboards measurements and drafts.

I have no idea what the formula/process is, does anybody know?

I realise there will never be a perfect straight line through all the freeboard measurements so this method must average the differences out.

Thanks for help.

2. Joined: Oct 2008
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have you looked at the ISO code?

3. Joined: Jan 2004
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### Raggi_ThorNav.arch/Designer/Builder

It's a lot of work to do this math manually.
Say you have measured some heights (y1, y2, y3 etc) at some given locations (x1, x2, x3 etc), then find a straight line Y = ax + b (calculate the constants a and b) so that the sum of the squared differences between all your measurments and the calculated Y is minimized.
Excel or OpenOffice does it for you.

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### Transom6.3New Member

Thanks guys,
I'll look into it and try and set up an excel spreadsheet.
Does anybody have an excel template.

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### Raggi_ThorNav.arch/Designer/Builder

6. Joined: Jan 2004
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### Raggi_ThorNav.arch/Designer/Builder

#### Attached Files:

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• ###### TrendLine.xls
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14.5 KB
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### Transom6.3New Member

Thanks alot Raggi,
That's a big help.

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