geoblacklight
Add imagery basemaps
Descriptive summary
It would be nice to provide options for imagery basemaps. (None of the current GBL basemaps include imagery.) Imagery would provide useful context for users previewing certain types of datasets.
Some possibilities are listed in leaflet-extras. HERE, Mapbox, and Esri all offer global imagery, but do require registration. Similarly, leaflet-bing-layer provides access to Microsoft Bing imagery, and again registration is required.
Each provider may have specific limits or terms of use, so we'd want to investigate and perhaps collate that info here, and perhaps make a recommendation for which providers would be easiest to incorporate into GBL.
Another possible source is https://viewer.nationalmap.gov/services/ -- several layers are listed under "Base Maps (Cached)":
- USGS Topo Base Map (not imagery, but very detailed)
- USGS ImageryOnly Base Map
- USGS Imagery Topo Base Map (imagery, plus topo lines and labels)
These USGS layers are quite detailed for the US, but also have global coverage, although only at lower zoom levels.
I'm not sure if these layers would be something that could be added to https://github.com/geoblacklight/geoblacklight/blob/master/app/assets/javascripts/geoblacklight/basemaps.js or whether it would be better to just add a wiki page with instructions.
I'd lean towards a wiki page. This should already be customizable doing something like this: https://github.com/sul-dlss/earthworks/commit/ebc9bb501b983c45532b724149de43f59674db61
Originally we had decided not to include proprietary based basemaps just to remove any questions of licensing. I'd be happy to revisit that if others want to do something else.
Yes, the licensing part is an obstacle. I've only started to investigate this, and it's not easy to even find the appropriate terms of service and free usage limits. If others are interested (during the next sprint, or Geo4LibCamp) maybe we could try to tackle this info-gathering as a group.
Also, what would you think of adding the HOTOSM and standard OSM basemaps to basemaps.js? I think people would be more likely to use those than others on the current list (like worldAntique) that don't have much detail.
To preview layers available in Leaflet-providers https://leaflet-extras.github.io/leaflet-providers/preview/
My vote is follow the advice of documenting the general approach to baselayer configuration more robustly in the customizations section of the wiki. Especially since there is now function for the base OSM layers, and adopters can insert layers of their choosing from the menu in the Leaflet-providers site.
