I'm using Drone2Map and Collector for field surveys. Drone2Map does not support Web Mercator Auxiliary Sphere for the GCPs and the Collector map is made in ArcGIS online that has a default coordinate system of Web Mercator Auxiliary Sphere. I have tried to add my own basemap to Arc GIS Online with the coordinate system I need--but when I try to share it the warning comes up that the web layer will used WGS 1984 Web Mercator (Auxilairy Sphere). I found a basemap in the portal that was GCS WGS84 and used that as a basemap and it worked in Collector (which I could use in Drone2Map, but I would really like UTM), so does anyone know where a UTM basemap of California is already in the portal, or how I can add a basemap with the coordinate system I need? Thank you very much!