External map layer

To add an external WMS layer to the tracking map.

sample map with swiss topo layer: https://racemap.com/player/swiss-topo-sample

URL to call external layer: https://wms.geo.admin.ch/?SERVICE=WMS&REQUEST=GetMap&VERSION=1.3.0&LAYERS=ch.swisstopo.swissimage&STYLES=default&CRS=EPSG:3857&BBOX={bbox-epsg-3857}&WIDTH=256&HEIGHT=256&FORMAT=image/png

more about swiss topo. https://www.geo.admin.ch/en/geo-services/geo-services/portrayal-services-web-mapping/web-map-services-wms.html

https://wms.geo.admin.ch/
     ?SERVICE=WMS
     &REQUEST=GetMap
     &VERSION=1.3.0
     &LAYERS=ch.swisstopo.swissimage
     &STYLES=default
     &CRS=EPSG:3857
     &BBOX={bbox-epsg-3857}
     &WIDTH=256
     &HEIGHT=256
     &FORMAT=image/png

SERVICE	WMS
REQUEST	GetMap
VERSION	1.3.0 or 1.1.0
STYLES	empty
CRS (1.3.0) or SRS (1.1.0)	EPSG:3857
BBOX	{bbox-epsg-3857} a variable
WIDTH	256; same as tile size respectively
HEIGHT	256; same as tile size respectively
FORMAT	image/png or image/jpeg
TRANSPARENT	true

LAYERS: different, available in GetCapabilities e.g. https://wxs.ign.fr/yourkey/geoportail/r/wms?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetCapabilities