Add USGS tileset options

[FishheadNate]

Expand map_service and map_type options to include U.S. Geological Survey (USGS) tilesets:

• USGS Hydro Cached

  basemap_ggplot(ext, map_service = "usgs", map_type = "hydro_cached") + theme_void()

  

• USGS Imagery Only

  basemap_magick(ext, map_service = "usgs", map_type = "imagery_only")

  

• USGS Imagery Topo

  basemap_magick(ext, map_service = "usgs", map_type = "imagery_topo")

  

• USGS Shaded Relief Only

  basemap_magick(ext, map_service = "usgs", map_type = "shaded_relief")

  

• USGS Topo

  basemap_magick(ext, map_service = "usgs", map_type = "topo")

  

[16EAGLE]

Thank you for taking the time to add this tile service! Would be nice to have this in the package.

When testing this with the default ext object of basemaps, I am getting 404 errors. Is there a limitation on the zoom level for these tile servers?

library(basemaps)
data(ext)

set_defaults(map_service = "usgs", map_type = "imagery_topo")
basemap_ggplot(ext)
#> Loading basemap 'imagery_topo' from map service 'usgs'...
#>  |                                                                                                     | 0 % ~calculating  
#> Error: Tile download failed: HTTP error 404.

Also, when I check the start tile and end tile links at https://basemap.nationalmap.gov/arcgis/rest/services/USGSHydroCached/MapServer, I get 404 errors starting with Level 9.

Any ideas?