Add H3 hexagons page: the globe on H3's icosahedron, unfolded

README.md

@@ -290,6 +290,27 @@ checked against s2sphere in `test/fixtures/s2-cells.json`. Hash keys: `lvl`
 (0 to 12), `t` (unfold, 0 globe, 0.5 cube, 1 net), `cell` (a token),
 `curve`, `grid`, `coast`, `uvgrid`, `cam`.
 
+## H3 hexagons
+
+`h3.html` puts [H3](https://h3geo.org/), Uber's hexagonal grid, on the
+icosahedron it is built on. A light at the centre of the globe casts every
+point onto one of twenty faces (the gnomonic projection, twenty times), and
+on each face's plane H3's hexagons are exactly regular. "Unfold" swells the
+globe to the icosahedron (placed as Fuller placed it for the Dymaxion map,
+every corner in the ocean) and opens it into the strip net. The twelve
+pentagons, one at each corner, are outlined at every resolution; "Children"
+shows the seven children of the picked cell spilling over its edge, and the
+19.1 degree turn between Class II and Class III resolutions.
+
+Click a cell for its index, resolution, base cell, faces and area, or paste
+an index. Parent and Child step through resolutions 0 to 15; GeoJSON copies
+the cell. The cells come from [h3-js](https://github.com/uber/h3-js) 4.4.0
+(from jsDelivr); `src/core/icosa.js` builds the icosahedron from H3's twelve
+pentagons, its gnomonic face frames and the hinges of the net, checked
+against h3-js in `test/check-icosa.mjs`. Hash keys: `res` (0 to 3), `t`
+(unfold, 0 globe, 0.5 icosahedron, 1 net), `cell` (an H3 index), `grid`,
+`kids`, `coast`, `col` (`base`, `digit`, `none`), `bm`, `cam`.
+
 ## MGRS and Sentinel-2
 
 `sentinel.html` shows UTM as one transverse Mercator cylinder laid on its
@@ -817,6 +838,7 @@ spilhaus.html, js/spilhaus.js          Spilhaus page
 globals.html, js/globals.js            globals and interrupteds page
 catastrophes.html, js/catastrophes.js  map catastrophes page
 cells.html, js/cells.js                s2 cells page
+h3.html, js/h3.js                      H3 hexagons on the icosahedron
 grids.html, js/grids-page.js           model grids page
 indexspace.html, js/indexspace.js      index space page
 structure.html, js/structure-page.js   tiles and overviews page
@@ -863,6 +885,7 @@ src/core/geotiff-write.js         GeoTIFF writer with user-defined CRS keys
 src/core/cellexport.js            GeoTIFF of one cell, tile or lobe in its own CRS
 src/core/mishaps.js               catastrophe steps, vertex-by-vertex and spherical drawing
 src/core/s2.js                    S2 faces, cell ids and tokens, from s2geometry
+src/core/icosa.js                 icosahedron from 12 vertices, gnomonic face frames, strip net hinges
 src/core/roms.js                  ROMS s-coordinate, synthetic grids and data, Zarr grid reader
 src/core/regular.js               which CRS makes a lon/lat array regular; example grids; geos scan angles
 src/core/structure.js             grid, tile and file structure of COG, Zarr, WMTS, ArcGIS, XYZ and specs

aatgrid.html

@@ -28,7 +28,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html" aria-current="page">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html" aria-current="page">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section class="embed-keep">

affine.html

@@ -25,7 +25,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html" aria-current="page">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html" aria-current="page">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section>

bins.html

@@ -28,7 +28,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./bins.html" aria-current="page">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html" aria-current="page">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section class="embed-keep">

catastrophes.html

@@ -29,7 +29,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html" aria-current="page">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html" aria-current="page">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section class="embed-keep">

cells.html

@@ -28,7 +28,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html" aria-current="page">s2 cells</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html" aria-current="page">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section class="embed-keep">

cones.html

@@ -29,7 +29,7 @@
   <aside id="panel">
     <header>
       <h1>playproj</h1>
-      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html" aria-current="page">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
+      <nav class="pages"><span class="group"><a href="./">Perspective</a><a href="./cones.html" aria-current="page">Cones and cylinders</a></span><span class="group"><a href="./spilhaus.html">Spilhaus</a><a href="./globals.html">Globals and interrupteds</a><a href="./tissot.html">Distortion</a></span><span class="group"><a href="./ellipsoid.html">Ellipsoid</a><a href="./geoid.html">Geoid</a><a href="./ortho.html">Orthorectification</a></span><span class="group"><a href="./cells.html">s2 cells</a><a href="./h3.html">H3 hexagons</a><a href="./bins.html">L3 bins</a><a href="./grids.html">Model grids</a><a href="./indexspace.html">Index space</a><a href="./sentinel.html">MGRS and Sentinel-2</a><a href="./aatgrid.html">AAT grid</a><a href="./structure.html">Tiles and overviews</a><a href="./rasterize.html">Rasterize</a><a href="./affine.html">Affine</a><a href="./regular.html">Regular in what?</a><a href="./hull.html">Convex hull</a></span><span class="group"><a href="./catastrophes.html">Catastrophes</a><a href="./texture.html">Texture mapping</a><a href="./example.html">For example</a></span><span class="group"><a href="./homage.html">Homage</a><a href="./vicgrid.html">VicGrid</a></span><span class="group"><a href="./nuyina.html">Nuyina</a><a href="./rhumb.html">Rhumb lines</a></span></nav>
     </header>
 
     <section class="embed-keep">