Base map + projection questions

[Dan_Weaver]

I’m planning on doing a lot of refactoring related to projections in a WPF app. I was reading through https://thinkgeo.com/blog/map-projections and noticed it mentions “base map” a few times. What is considered a base map in this case? My app is strictly offline and I just create some overlays and have various layers in them.

I have many different layers from different formats that could be one of many different types of projections. Do I only have to worry about making sure the external projection of these layers are the same and that the map unit matches what the external projection’s measurement of unit is?

I’m still on v13* if that matters.

Currently I only allow two projections: WGS84 and web mercator. Whenever I switch between them, I simply change the map’s MapUnit to either DecimalDegree or Meter, and then loop through all the layers to set their external projection. There is no projection on the map object itself though right? I don’t see any properties related to it at least.

Thanks!

[ThinkGeo_Products]

Hi Dan,

In the context of the blog post, a basemap is something like googe, azure or other online provider. Often times, these providers will only offer their maps in Web Mercator. As a result, it’s easier to just reproject your data to Web Mercator (3857) since it’s more time-consuming to try and reproject the basemap data provided by google, azure, etc.

You’re correct that there’s no project on the map object itself and you’re correct in just setting the external projection of each layer that needs reprojected.

Thanks,
John