I downloaded some DEMs from the USGS with a resolution of 1/3 degrees for different areas in the US.
Now I am looking at the files and saw that all DEMs have the same number of columns and rows.
I measured the dimensions of the area covered by different DEMs and found that all have a similar length in N-S direction, but that their dimension in W-E direction varies a lot, being larger towards the south.
So now I am a bit confused. I know that the length of one degree longitude is larger near the equator than at the poles, so if my DEMs have a resolution of 1/3 degree I thought the number of columns in the DEMs for areas located in the north would be smaller than for areas located towards the south, but this is not the case.
On the other side, if DEMs at the north and south have the same number of columns, but cover areas of different dimensions, then the resolution must be different in both cases ...
Can someone help?