measuring issue with imageJ

[mizuki]

For my research i have to measure snails(physa acuta) , i've measured them both with a caliper and imageJ, imageJ does not give me the proper measurements, i think it could be because of the concave nature of the shell. Does anyone know a way to accurately measure concave structures?

[Michael Doube-3]

Hi Mizuki,

On 23.08.11 11:11 PM, mizuki wrote:
> For my research i have to measure snails(physa acuta) , i've measured
> them both with a caliper and imageJ, imageJ does not give me the
> proper measurements, i think it could be because of the concave
> nature of the shell. Does anyone know a way to accurately measure
> concave structures?

Perhaps the 'rotating calipers' measurement is what you need (but maybe
not; it's for convex structures).  It is implemented in ImageJ as Feret
Diameter (which you can select in Analyze > Set Measurements), and the
result is listed as MinFeret in the Results table.

See this for more info on rotating calipers:
http://cgm.cs.mcgill.ca/~orm/rotcal.html

I hope this helps - if you need more assistance please make a diagram of
the problem so we can help you better.

Michael