# Questions tagged [dggs]

Questions related to Discrete Global Grid Systems (DGGS)

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### Why are discrete global grids vs. making a custom grid using a tesselation different in size and shape?

I need an equal area grid system that can vary in area (i.e. 100km2 to thousands). I have two ways of doing this at continental scales (Asia + Europe as an example). One way is to create a tesselation ...
• 193
1 vote
45 views

### How does the ISEA-projection work? Looking for a didactic algorithm description

Is it a direct projection on 20 faces or on 32 faces? Can I use PostGIS (with ISEA) to calculate and obtain cell-identifiers? For hexagons (like Uber H3) or for diamonds (like DGGRID's ISEA4D). The ...
• 2,304
262 views

### H3 Hexagon Geometry join on MSA Geometry

I have a pandas DataFrame with h3 hex ids and corresponding Polygon geometries and a geojson file with Texas Metro Area Geometries. I'd like to join the H3 hex ID to Metro area and identify which ...
• 483
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### How to obtain the minimal covering of a circle with H3 hexagons?

Given an EPSG:4326 lon,lat coordinate pair, and a radius r in meters, I want to find the smallest set of H3 hexagons at resolution res that completely covers the circle centered at lon,lat with radius ...
• 231
1 vote
437 views

### Safe upgrade of PROJ for PostGIS?

Is there a safe way to install fresh PROJ, for example v8.2, in a Debian Linux server, for use with (for example) PostGIS v3? The installation of PROJ was implicit in the PostGIS's, I never do ...
• 2,304
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### Converting line to set of H3 hexagons?

What is a proper way to convert a GeoJSON linestring to a set of H3 hexagons? I came up with an algorithm where I extract points from a line, calculate an H3 hexagon of these points geo_to_h3 connect ...
• 133
321 views

### How to use ISEA projection?

The projection named ISEA - Icosahedral Snyder Equal Area has a (supposedly) good implementation in the PROJ Library, proj.org/isea, that is used by PostGIS, QGIS, etc. The example is agnostic - was ...
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### Distorted h3 hexagons using h3js with Mapbox

When a user clicks on a Mapbox streets-v11 map, I'm attempting to: Take the clicked point, and identify the h3 hexagon (at resolution 10) around the point Convert the hexagon coordinates into the ...
• 121
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### Why are my icosahedron triangle subdivisions not equilateral (PostGIS)?

I am creating a geodesic polyhedron using PostGIS. I am dividing the base icosahedron points (see Appendix A), into the first level of Class I subdivisions. The setup For simplicity let's take just ...
• 183
470 views

### Generate global grid of circles with minimum overlap with PostGIS

I want to generate a table of geometry points in PostGIS which represent the centers of circles, each with the same radius of X meters, that together form a "grid" that covers the entire ...
• 183
338 views

### DGGS projections with PostGIS or pgLatLon

Important DGGS projections (like ISEA4T, ISEA4D or ISEA7H variants of ISEA) are free at https://github.com/sahrk/DGGRID , the DGGRID Software Project, but I not see how to use it with PostGIS. Only ...
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160 views

### Is there a FOSS implementation for Discrete Global Grid System & Global Statistical Geospatial Framework?

This 2019 document, "GSGF Europe -Implementation guide for the Global Statistical Geospatial Framework in Europe" describes the harmonization of two standards: INSPIRE D2.8.I.2_v3.1 of year 2014; OGC'...
• 2,304
1 vote
211 views

### Is there a piecewise-UTM coordinate system?

Is there an EPSG code, WKT or a proj4 string, for a single global piecewise-UTM coordinate system such as MGRS (the NATO military grid reference system)? I suppose this would work similar to the ...
• 476
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### Uber H3 DGGS: Table of largest hexagons per resolution?

I'm evaluating the use of H3 as a DGGS for a project, and so far I've been unable to find any reference of the area of the largest and smallest hexagons in the grid at each resolution. The "official" ...
• 257
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### Hex grid on EPSG:4326 globe (for use in Leaflet)

I'm looking for a way to evenly distribute a hexagon grid (x,y,z) on the EPSG:4326 globe. Knowing this is not mathematically possible I'm accepting the following limitations: Poles don't need ...
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