Lua H3 provides a Lua binding for the H3 library. H3 is a hexagonal hierarchical geospatial indexing system.

Here is a quick example:

local h3 = require("h3")

local lat, lng = 47.37, 8.55
print(string.format("Coordinates: %.4f %.4f", lat, lng))
local cell = h3.latlngtocell(lat, lng, 8)
print(string.format("Cell at resolution 8: %x", cell))
local lat, lng = h3.celltolatlng(cell)
print(string.format("Centroid coordinates: %.4f %.4f", lat, lng))
local parentCell = h3.celltoparent(cell, 7)
print(string.format("Parent cell at resolution 7: %x", parentCell))
local childCells = h3.celltochildren(parentCell, 8)
for i, childCell in ipairs(childCells) do
        childCells[i] = h3.h3tostring(childCell)
end
print(string.format("Child cells at resolution 8: %s", table.concat(childCells, " ")))

Output:

Coordinates: 47.3700 8.5500
Cell at resolution 8: 881f8ed957fffff
Centroid coordinates: 47.3711 8.5488
Parent cell at resolution 7: 871f8ed95ffffff
Child cells at resolution 8: 881f8ed951fffff 881f8ed953fffff 881f8ed955fffff 881f8ed957fffff 881f8ed959fffff 881f8ed95bfffff 881f8ed95dfffff

You may need to build and install H3 in order to build Lua H3. Please see the H3 installation documentation.

To build a shared library, you can add -DBUILD_SHARED_LIBS=1 to the H3 cmake call. Alternatively, you can add -DCMAKE_POSITION_INDEPENDENT_CODE=1 to the H3 cmake call to ensure the static H3 library can be linked into a dynamically shared object.

To build and install with LuaRocks, run:

luarocks install lua-h3

Lua H3 comes with a simple Makefile. Please adapt the Makefile to your environment, and then run:

make
make test
make install

Please see the release notes document.

Please browse the documentation folder for the extensive documentation.

Lua H3 supports Lua 5.3, and Lua 5.4.

Lua H3 has been built and tested on Ubuntu Linux (64-bit).

Lua H3 is released under the MIT license. See LICENSE for license terms.