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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 ...
Leo Ohyama's user avatar
1 vote
0 answers
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 ...
Peter Krauss's user avatar
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-1 votes
1 answer
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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 ...
kms's user avatar
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3 votes
1 answer
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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 ...
shadowtalker's user avatar
1 vote
0 answers
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 ...
Peter Krauss's user avatar
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3 votes
3 answers
2k views

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 ...
gman's user avatar
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5 votes
2 answers
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 ...
Peter Krauss's user avatar
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2 votes
3 answers
2k views

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 ...
amatur's user avatar
  • 121
8 votes
1 answer
212 views

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 ...
poshest's user avatar
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5 votes
0 answers
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 ...
poshest's user avatar
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6 votes
1 answer
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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 ...
Peter Krauss's user avatar
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4 votes
1 answer
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'...
Peter Krauss's user avatar
  • 2,304
1 vote
0 answers
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 ...
benjimin's user avatar
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4 votes
1 answer
1k views

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" ...
DanM's user avatar
  • 257
5 votes
2 answers
2k views

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 ...
ajthinking's user avatar