I've been trying to map an area of 35 images. Since they were in UTM I converted to Mercator projection using
gdalwarp. I then tried to merge the images with the command:
gdal_merge -init 255 -o I:\newfilename.tif --optfile imagelist.txt
which produced a mosaic that had missing data where each image would have overlapped, similar to black grid lines.
I made sure that the order of images in my text file was arranged in order but can't figure out what else it could be. I'm completely new to coding so anything helps.