Interactive web app for exploring HEALPix (and other DGGS) grids

[VeckoTheGecko]

Motivation

(point 1) Lots of the visualisations of HEALPix grids are either grainy diagrams or photos from astronomical HEALPix. This makes it potentially difficult to explain or understand HEALPix, especially in a geospatial context.

(point 2) I feel that users might be some usecases where users would want to "explore the globe" and see where the HEALPix grid cells lie at different resolutions:

• maybe they want to model a certain feature, and they want to quickly check what resolution they would need
• maybe they want to model a certain region, and want to make sure the region doesn't stradle gridcells in a weird way that will mess with analysis
• Maybe they want to select a region, but using a geopolygon isn't specific enough (they want to include/exclude specific cells)
• ... (please comment below your thoughts on usage)

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Both of these points could be addressed by a web app where users can explore the world and select HEALPix cells. They could then export these cells to a MOC file.

Scoping the project

in scope:

• Explore the world with a HEALPix grid overlayed on top with gridlines (OSM layer), and cells are labelled with the IDs

• Users can select cells

• Users can change the grid refinement level (their previous selection persists)

• choose grid (HEALPix for MVP, other grids later)

• Implementation details:

  • (not for the MVP, but in future) everything under the hood should be stored as MOCs for the sake of efficiency and easy export/import and import into xdggs

out of scope:

• Any sort of visualising real DGGS data. This would be mainly a tool to solve (1) and (2).
• Use a geopolygon/shapefile to highlight gridcells
  • this would be able to be done in xddgs via a polygon select and then ddgs.explore()
• non DGGS grids
• astronomical applications/features
• (for the MVP) looking beautiful

My questions:

• Do you think this would be useful to those working with DGGS?
• Thoughts on scope?
• Where would this project live?

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I don't propose that this would be incorporated into xdggs since (a) seems a tangent from the current goals, and (b) perhaps a standalone website is even more useful. I just didn't know where else to have this discussion.

[VeckoTheGecko]

Woah, ok a bit uncanny. I just came across a video posted last week by Qiusheng Wu about this for the MGRS

https://youtu.be/z2oXPh8QI04?feature=shared

[tinaok]

@VeckoTheGecko you might have already seen it but @tobi made this tool, https://github.com/d70-t/gridlook
Example of visualisation : https://gridlook.pages.dev/#https://swift.dkrz.de/v1/dkrz_41caca03ec414c2f95f52b23b775134f/reanalysis/v1/ERA5_P1M_7.zarr

Your suggested point "Explore the world with a HEALPix grid overlayed on top with gridlines (OSM layer), and cells are labelled with the IDs" might be able to added in the functionality of Tobi's tool?

It can today only visualise total healpix grid, not regional ones (indicated regional data in coordinate)

cc: @keewis

[tinaok]

p.s. may be better to make a section in https://github.com/pangeo-data/awesome-HEALPix listing visualisation tools?