Use Case: Display map coverages or other custom tile data

[AmeliaBR]

This issue is for discussion of the map viewer use case “Display map coverages or other custom tile data”, its examples & list of required capabilities.

I've combined these two use cases — data coverages and custom tiles, including aerial/satellite imagery — because they are technologically equivalent; the required capabilities are the same.

But maybe it would be helpful to separate them out for the examples?

When talking about coverages separate from custom tiles, though, the examples will often cross into the multiple layers use case. So maybe the data coverage examples can be part of that use case, and this one can focus on custom imagery or coverages that have been server-rendered onto a base map?

[AmeliaBR]

Data coverages (= heatmaps) is one of the items mentioned in Mila Frerichs JS map framework comparison table

When I sketched out this use case, I was assuming that a heatmap would need to be pre-rendered in other software, and that's why I was grouping it with custom tile/image layers. But it seems many of the libraries can generate a heatmap from vector data, with dynamic styling client side.

Links to reference tools:

• OpenLayers docs, example

• Leaflet: doesn't seem to be a standard built-in feature, but there are multiple heatmap-related plugins in the official directory

• Mapbox: docs, example, tutorial

[prushforth]

Are you using "data coverage" as a synonym for heatmap? This could reflect the need for a definition. It seems heatmap is a term common to the libraries you link to. "Coverage" has a specific raster geo data connotation i.e. satellite imagery or other pixel-based format that contains data on a per-pixel basis.

But maybe it would be helpful to separate them out for the examples?

I think perhaps that's a good idea. I believe that most coverage data isn't rendered as such, but images which represent the coverage data can be/are. The content can be served up in a similar interface, however, so putting my MapML hat on, I think it could be useful to be able to link to coverage data while simultaneously displaying images representing that data. A GIS system could use the coverage links for retrieving coverages for calculations/operations, while a browser might ignore the coverage links and only render the image links.

In briefly reviewing the heatmap examples you link to, it seems like an area that CSS/SVG and MapML could work together in a suitable browser equipped to support the use case.

[AmeliaBR]

Heatmaps, as a special way of displaying vector data (points + intensity data), is now a separate use case. Sorry for confusing that. Of course, heatmaps generated ahead of time or on the server and displayed as custom data coverage layers would still be covered here.

That said, I think we still need another use case. After merging the widget & API use cases, I find that this one is trying to do too much. For authors, the two use cases are wanting to use existing map services or map tile sets, vs wanting to use your own content. However, from a technical/API perspective, for the example files, the main distinction is between using a tileset and using a single image.

[AmeliaBR]

Either way, we should probably change these examples to use map sources that aren't "built in" to the libraries, like OpenStreetMap is.

[AmeliaBR]

So maybe there should be four use cases, remembering that these are also now the use cases for the data format / server API section:

• use a WMTS-conformant web map tile service
• use a tileset that is defined by a REST API/URL template
• use a WMS-style single-image map source as a map layer
• use custom imagery as a map layer (either single image or dividing it into tiles, but without hosting a full GIS server)

[shepazu]

It seems like "maps of non-Earth bodies such as Mars and the Moon" is out of place here. Those would be separate maps, not layers or coverages on a map of Earth.

[prushforth]

It seems like "maps of non-Earth bodies such as Mars and the Moon" is out of place here.

Such maps could easily be accommodated in a standard if the coordinate systems associated to the non-Earth bodies is known/standardized (as a TCRS).

[prushforth]

But to your point, coverage support the subject of this use case, and I agree with you.

[caseymm]

Just wanted to give a heads up that the title for this issue in the maps4html use case doc doesn't quite align with the title for this issue here (and that the title here makes more sense).

[Malvoz]

Thanks @caseymm, I think the title as described in https://github.com/Maps4HTML/HTML-Map-Element-UseCases-Requirements/issues/38#issue-448626305 is even clearer, and more consistent with other use case titles, changing to that.