Subtracting 3d datasets

I have two datasets both with the same amount of X,Y,Z points. I wish to subtract one from the other obtaining the change in the depth from the 2 sets. Is a mesh grid still the best option or do I lose the Z values?

Answer 1

[Kirby Fears]

Hi Jessica,

Can you store the data in a three dimensional array?

Can you also try to explain the operation more clearly? I'm not exactly sure what you meant:

"I wish to subtract one from the other obtaining the change in the depth from the 2 sets."

Here's a simple example that might help:

>> threes=3*ones(5,5,5);
>> twos=2*ones(5,5,5);
>> result=threes-twos;

[Jessica Sanow]

The datasets are point cloud images of an area, one with snow and one without. So the goal is to take dataset 1 and subtract it from dataset 2 and hopefully giving a snow depth. So what I am trying to figure out is if I should make some sort of interpolation or if there is a simple way to subtract the two datasets. Hopefully this helps clarify what I am looking for.

[Kirby Fears]

I see. Hopefully a user of the Computer Vision System toolbox can answer this. It would be good to update your post to specifically say 3-D point cloud.

Sorry I'm not familiar with manipulating the point cloud data structures.

If you can extract simple arrays from your data structure, it sounds like each point clouds could be simplified to a A x B matrix where each element of the matrix is the Z value. Where element (a,b) of the first pc's matrix has the same (x,y) coordinate as element (a,b) of the second pc's matrix. Then you could simply subtract the two matrices.