I have four .HGT topography tiles (tile1,tile2,tile3,tile4 in the photo below). They are in geographic coordinate system. I would like to merge those four tiles, and then from that merged raster layer to cut off a piece (green rectangle in the photo) and to make a new raster layer from that cut off green rectangle piece.
The corners of the rectangle are suppose to be defined by adding 10 degrees of latitude and longitude to the central point (55,-2) of the green rectangle piece:
How can this be done in QGIS? How can four .HGT raster files be merged and then a new raster layer cut off from it?