Open Topo Map https://a.tile.opentopomap.org/$z/$x/$y.png Open Street Map http://tile.openstreetmap.org/$z/$x/$y.png USGS Topo https://navigator.er.usgs.gov/tiles/tcr.cgi/$z/$x/$y.png USGS Imagery https://navigator.er.usgs.gov/tiles/aerial_Imagery.cgi/$z/$x/$y