vq = griddata(x,y,v,xq,yq)
For that syntax, x, y, and v need to be vectors.
Your equivalent to v, Z in your code, is a vector of length 24 x 1, which is fine in itself.
Your x and y start out at 76 x 88 . Neither of those are vectors. They also are not multiples of length 24 (your Z). Your x and y need to be the same length as your z.
Now, if you had an x which was 76 x 88, and a y which was 76 x 88, and a z the same size, then you could
griddata(x(:), y(:), z(:), xq, yq)
for some xq, yq
Your variables give the impression that you have data for a single X/Y plane, and you have a vector of Z values that you want to make predictions at. That is not going to work: you (x, y, z) triples as input to make predictions against.
