I got a shaded-relief image for North America from the USGS but it is not georeferenced.
Attached are the characteristics of the image in ArcCatalog, and the extent was filled-in by the .tfw file I made, as attached.
Looking at the image, I guessed the upper-left corner was long -130 and lat +60. Still according to the image, I found the upper-right corner long -50 and lat +60 while bottom-left long -130 and lat +15
With 9600 columns, the cell size would be: (130-50) / 9600 = 0.008333333°, which is 30''. Looks good
And with 7240 rows, the cell size would be: (60-15) / 7240 = 0.006215469°, whi ch is roughly 22''. Not as good.
Even with a .tfw with these values do not update the Cell Size in the image in ArcCatalog. Why? Usually, it does...
Also, would it be possible to have rectangular pixel? I guess why not...
Does the number of bands, which are 3, change anything in georeferencing the image? How could I convert the image from 3 bands to 1 bamd only?
Thanks for your help