Chord length to measure moments of area

[Robert Jones]

Hello all,

I'm trying to measure the shape of insect wings. Specifically I would  
like to be able to calculate moments of area.

The Circularity and Moment Calculator plugins don't give me quite the  
details I need as I'm looking for measures of chord length. To do  
this, I just need a plugin that will give me coordinates of x at set  
increments of y.

So, if my figure has attached properly, I'm looking for measures of  
'c' at set increments of 'r' along the major axis 'R'. The strip  
diameter 'dr' could be something like 10 pixels (I can manually  
orientate each image so that 'R' lies horizontally). From this I can  
then calculate the first, second and third moments of area and their  
non-dimensional radii. The idea is to use imageJ to make the same kind  
of measurements that were taken by hand in the old days (eg Ellington  
1984 Phil Trans Roy Soc, 305:17-40; Betts and Wootton 1988 J Exp Biol  
138:271-288).

Please let me know if you know of a plugin that I could use. I don't  
have any programming experience so it would take me forever to put  
something together myself.
Thanks very much
Robert

[Michael Doube-3]

Hi Robert

> I'm trying to measure the shape of insect wings. Specifically I would
> like to be able to calculate moments of area.
BoneJ's Slice Geometry calculates second moment of area, and maximum
chord length for calculation of section modulus.
http://bonej.org/slice

> The Circularity and Moment Calculator plugins don't give me quite the
> details I need as I'm looking for measures of chord length. To do this,
> I just need a plugin that will give me coordinates of x at set
> increments of y.
Chord length as a function of axial displacement is not implemented in
BoneJ, but could be with a bit of a hack.

> So, if my figure has attached properly,
Yes, it did - very informative, thank you.

>(I can manually orientate each
> image so that 'R' lies horizontally).
That won't be necessary. Let me know how far you get with Slice Geometry
and then we can discuss if you want any further features.

Cheers,

Michael

[Robert Jones]

Hi Michael,

This is terrific thanks. I can use the second moment of area output  
directly in my equation for the non-dimensional radii, so this is  
really all I needed the chord lengths for.

I've been very impressed with the tools available for ImageJ.

Thanks again
Robert


Quoting Michael Doube <[hidden email]>:

> Hi Robert
>
>> I'm trying to measure the shape of insect wings. Specifically I would
>> like to be able to calculate moments of area.
> BoneJ's Slice Geometry calculates second moment of area, and maximum
> chord length for calculation of section modulus.
> http://bonej.org/slice
>
>> The Circularity and Moment Calculator plugins don't give me quite the
>> details I need as I'm looking for measures of chord length. To do this,
>> I just need a plugin that will give me coordinates of x at set
>> increments of y.
> Chord length as a function of axial displacement is not implemented in
> BoneJ, but could be with a bit of a hack.
>
>> So, if my figure has attached properly,
> Yes, it did - very informative, thank you.
>
>> (I can manually orientate each
>> image so that 'R' lies horizontally).
> That won't be necessary. Let me know how far you get with Slice Geometry
> and then we can discuss if you want any further features.
>
> Cheers,
>
> Michael
>
>