In order to simplify code, most terrainr functions expect a set S4 class representation of coordinate pairs and bounding boxes. If the provided data is not in the expected S4 format, these functions are used to cast the data into the target class.
bl, tr: The bottom left (bl) and top right (tr) corners of the bounding box, either as a terrainr_coordinate_pair object or a coordinate pair. If the coordinate pair is not named, it is assumed to be in (lat, lng) format; if it is named, the function will attempt to properly identify coordinates.
coord_units: Arguments passed to terrainr_coordinate_pair . If bl and tr are already terrainr_coordinate_pair