-------- Original Message -------- Subject: How to determine landmark density in patches and curves for a specific area? Date: Thu, 27 Oct 2011 06:25:23 -0400 From: hmi hmi <[email protected]> To: morphomet morphometrics.org <[email protected]> Dear morphometricians, How do you determine the amount of landmarks needed for patches and curves for a specific area? Does over-landmarking generate meaningful results? Landmarking a surface very sparse would result in under representation. Is there some sort of golden rule to follow? I've used resample.exe to resample down a 100-90+ landmarks to 20 of the orbital shape of human skulls. I notice that some skulls have supra-orbital notch, some don't. The resampled results show a circular shape without the notch, though in morphoJ I could see the vector arrows around the region of the notch, though that is only found on the 7th PC (around 2.5%). Another example would be using a patch function in the IDAV landmark software. Lets say I place a patch on the temporal bone. Since this region is quite smooth I am not sure how dense I have to make the patch. It would be useful if there is some sort of virtual 3D scale/ruler which could wrap around the surface of the object as the density could be referenced to scale. However I am not sure if that kind of software exists. Thank you Helmi Pritam [email protected]
