Open Topo Map https://a.tile.opentopomap.org/$z/$x/$y.png 16 4UMaps http://4umaps.eu/$z/$x/$y.png 15 Open Street Map http://tile.openstreetmap.org/$z/$x/$y.png 19 USGS Topo https://navigator.er.usgs.gov/tiles/tcr.cgi/$z/$x/$y.png 15 USGS Imagery https://navigator.er.usgs.gov/tiles/aerial_Imagery.cgi/$z/$x/$y 15