I'm writing with a question regarding unexpected returns on a slope analysis using DTM LiDAR data at the scale of 2m in QGIS.
This is for my MSc dissertation (UK) which is due in about 6 months, so I want to be thorough.
I carry out the analysis I transformed the DTM raster data into slope raster data using QGIS slope Raster Terrain Analysis function - output format = GeoTIFF with Z factor of 1. I then converted the raster slope data into vector data (polygon) using the raster to polygon function. When I review some points on the map, they don't seem to align with what I know of the land (a few degrees off).
I should note that I have my map (including vector point data) in the WGS 84 Pseudo Mercator CRS whereas my DTM in data requires OSGB 1936 to overlap.
Perhaps I'm missing something, or are the slope outputs are correct?
LiDAR data was sourced from link provided below. https://data.gov.uk/harvest/gemini-object/33e78ae5-27d9-44db-9e2c-2e75c049e09c