Switch to Different Basemap than Mapbox

[rajadain]

Mapbox is deprecating Mapbox Classic styles in the spring:

Ahead of deprecation, here are the two key dates that you should be aware of:

• March 31, 2020 - you will no longer be able to upload new Studio Classic styles or modify existing Studio Classic styles via the Uploads API
• June 1, 2020 - you will no longer be able to make valid API requests using Studio Classic styles

They recommend switching to the Static Tiles API or Static Images API (both of which are significantly more expensive than the Raster Tiles API we're currently using), or switching Leaflet out in favor of Mapbox GL JS, which is prohibitively complex and expensive given the extensive use of Leaflet in the app.

Given this, the only option we have is to switch away from Mapbox for the default basemap. Evaluate basemap alternatives and replace the current one with it. Try to find something visually similar, so as not to be too jarring a change.

Some initial places to look:

• https://www.arcgis.com/home/group.html?id=702026e41f6641fb85da88efe79dc166&view=list&categories=%5B%22%2FCategories%2FWeb%20Mercator%22%5D#content
• https://viewer.nationalmap.gov/help/3.0%20TNM%20Base%20Maps.htm
• https://leaflet-extras.github.io/leaflet-providers/preview/

[rajadain]

The USA Topo Map looks good from afar:

But isn't really usable at higher zoom levels:

[rajadain]

Streets with Relief looks promising:

I suspect it is using a combination of vector layer (for the streets) and raster (for the relief). Not sure if our Leaflet setup can handle vector layers.

The topographic features are not as prominent as USA Topo above. Furthermore, the map is less legible, both in terms of labels and topography, than our current MapBox:

[rajadain]

The USGS has a topographic basemap of their own, which looks like this:

The labeling and topography on this is pretty neat, although with a greater emphasis on streets than we've had before. Unfortunately, this map colors urban areas red (probably a nod to NLCD), which will conflict with our NLCD overlays.

[rajadain]

The simple topographic map from ESRI is also promising:

The colors are plain and friendly, will not conflict with overlay layers. It does not have an oppressive amount of streets highlighted. The labels aren't the prettiest: most of them have significant kerning issues, but that may be nitpicking.

[rajadain]

The USGS also has a HydroCached basemap designed for hydrological study, which looks like this:

This seems to mainly add some relevant information above the simple topographic map above. Unfortunately, the labels overlap and clash in many places.

It should also be noted that the USGS provided maps seem to have worse performance than the native ESRI ones.

[rajadain]

The Terrain with Labels map has really prominent terrain:

But with no green on the map looks really bland. Furthermore, as another combination of vector and raster data, the zooming is janky.

[rajadain]

The National Geographic map is also a good contender:

It has good state outlines, labels, and topography. The strong colors give it quite a bit of character, although the usage of different fonts may be too interesting.

[rajadain]

I've deployed a version to staging that has the ESRI World Topo and the National Geographic basemaps.

Of the two, I would recommend ESRI World Topo, for the following reasons:

• It does not focus on streets and political boundaries like National Geographic does
• It has labeled contour lines for assisting with custom shape drawing:
• The muted colors are a good fit for interacting with the rest of the app, which frequently has overlays