I have extracted a DEM tile from the UK Ordnance Survey's free OS Terrain 50 dataset The tile contains spot heights for a grid comprising 51 nodes (West to East) by 51 nodes (North to South) with inter-node spacing 50m giving areal coverage of 2500m x 2500m.
Now I wish to copy (for private use only) a satellite image from Google Earth (non-pro version) and apply it as a texture to the 3D viewer app. I can do this in a rough and ready way by screen-snapping an image from Google Earth, then pasting the image into a paint program and then cropping and re-sizing. I have done this manually in a rough way but getting accurate location and boundaries for the image will be laborious. Also I expect that there may be horizontal positioning errors due to differences in the projections used by OS Grid and Google Earth.
I would like to know if there is a better way of extracting and processing the satellite image (using free software) to fit it to the DEM grid?