Hi Anna,
This situation comes up a lot. If the tiff data are regular in lat/lon, you'll need to know the extents (in lat and lon) of the data and the resolution (in degrees) of the data. If the data are in regular distance (meters or kilometers), you'll need to know the extents of the x,y coordinates and the spatial resolution of the grid. Then make a grid with meshgrid. So if your data are regular in geo coordinates, maybe it's
[lon,lat] = meshgrid(-180:0.25:180,90:-0.25,-90);
for a 1/4 degree global grid. There's a good chance the pixel centers would actually be offset by 1/8 degree, but you get the idea. Then should be able to use imread to read the geotiff, whether it does or does not have geo coded information. Something like
Z = imread('myfile.tif');
And then use interp2 to interpolate.
zi = interp2(lon,lat,Z,loni,lati);
You might have to tinker with flipping the image via fliplr or flipud, and you might have to do a rotation with rot90. Just check to make sure everything is in the right place with
pcolor(lon,lat,Z)
or
pcolor(x,y,z)
Before interpolating.
