I'm attempting to create a DEM from OS Terrain 50 data (ASCII Grid data) in QGIS.
The data is provided as multiple zipped folders representing sub divisions of OS grid squares. Each zipped folder contains an .asc file, a .gml file, and two .xml metadata files.
Dragging and dropping an .asc file into a layer gets me a DEM raster. The problem is that when I add adjacent .asc files, the created rasters don't blend. The edges have different brightness levels giving a tiling effect.
What am I doing wrong?