I am trying to overlay a set of Landsat images for the same band that were taken for the same Path/Row number but which were taken one year apart, eg April, 1998, 1999, 2000, 2001 etc.
The aim is to reduce the effects of yearly variability as I am interested in the geology, and summing the pixel values will (hopefully) highlight that and reduce the effect of fires, regrowth etc.
The problem is that the images are not covering exactly the same geographic space. The LL x-value varies by over 1400m in the images. The overlay function seems to sum the pixel values for their same location in the image array and not their geographic location. This offsets the features in the composite image so I get e.g. three rivers in the composite of three images and general blurring of the composite.
A possible fix would be to pansharpen the images, change them so the pixels start on the same geographic location, mask them so they show the same geographic extent and then process them.
Please, Is there an easier way???
