[rav]

Digital elevation models typically represent terrain elevations in a grid of square cells of some cell size, e.g. 1 meter by 1 meter. Such a model is rarely useful unless it also has georeferencing information, i.e. coordinates for the bounding box of the grid. Such coordinates can of course be arbitrary, but for large-scale mapping some convention is typically used so that adjacent models of the same cell size will "line up" without small gaps or overlaps. For example, this can be achieved by making sure that the grid corners are on integer coordinates - from my experience this is the convention I've seen in most European countries. In Poland, they instead use the convention that the centers of the corner cells are on integer coordinates, meaning everything is "off" by 0.5 meter (half a cell). This has caused me quite some difficulties at $WORK...