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13 items tagged “geojson”

2024

mapshaper.org (via) It turns out the mapshaper CLI tool for manipulating geospatial data—including converting shapefiles to GeoJSON and back again—also has a web UI that runs the conversions entirely in your browser. If you need to convert between those (and other) formats it’s hard to imagine a more convenient option. # 23rd March 2024, 3:44 am

Claude and ChatGPT for ad-hoc sidequests

Here is a short, illustrative example of one of the ways in which I use Claude and ChatGPT on a daily basis.

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2023

Geospatial SQL queries in SQLite using TG, sqlite-tg and datasette-sqlite-tg. Alex Garcia built sqlite-tg—a SQLite extension that uses the brand new TG geospatial library to provide a whole suite of custom SQL functions for working with geospatial data.

Here are my notes on trying out his initial alpha releases. The extension already provides tools for converting between GeoJSON, WKT and WKB, plus the all important tg_intersects() function for testing if a polygon or point overlap each other.

It’s pretty useful already. Without any geospatial indexing at all I was still able to get 700ms replies to a brute-force point-in-polygon query against 150MB of GeoJSON timezone boundaries stored as JSON text in a table. # 25th September 2023, 7:45 pm

TG: Polygon indexing (via) TG is a brand new geospatial library by Josh Baker, author of the Tile38 in-memory spatial server (kind of a geospatial Redis). TG is written in pure C and delivered as a single C file, reminiscent of the SQLite amalgamation.

TG looks really interesting. It implements almost the exact subset of geospatial functionality that I find most useful: point-in-polygon, intersect, WKT, WKB, and GeoJSON—all with no additional dependencies.

The most interesting thing about it is the way it handles indexing. In this documentation Josh describes two approaches he uses to speeding up point-in-polygon and intersection using a novel approach that goes beyond the usual RTree implementation.

I think this could make the basis of a really useful SQLite extension—a lighter-weight alternative to SpatiaLite. # 23rd September 2023, 4:32 am

2022

geoBoundaries. This looks useful: “The world’s largest open, free and research-ready database of political administrative boundaries.” Founded by the geoLab at William & Mary university, and released under a Creative Commons Attribution license that includes a requirement for a citation. File formats offered include shapefiles, GeoJSON and TopoJSON. # 24th March 2022, 2:03 pm

2021

Weeknotes: Velma, more Django SQL Dashboard

Matching locations for Vaccinate The States, fun with GeoJSON and more improvements to Django SQL Dashboard.

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country-coder (via) Given a latitude and longitude, how can you tell what country that point sits within? One way is to do a point-in-polygon lookup against a set of country polygons, but this can be tricky: some countries such as New Zealand have extremely complex outlines, even though for this use-case you don’t need the exact shape of the coastline. country-coder solves this with a custom designed 595KB GeoJSON file with detailed land borders but loosely defined ocean borders. It also comes with a wrapper JavaScript library that provides an API for resolving points, plus useful properties on each country with details like telepohen calling codes and emoji flags. # 18th April 2021, 7:37 pm

2020

Things I learned about shapefiles building shapefile-to-sqlite

The latest in my series of x-to-sqlite tools is shapefile-to-sqlite. I learned a whole bunch of things about the ESRI shapefile format while building it.

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Weeknotes: Shaving yaks for Datasette Cloud

I’ve been shaving a lot of yaks, but I’m finally ready to for other people to start kicking the tires on the MVP of Datasette Cloud.

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geojson-to-sqlite (via) I just put out the first release of geojson-to-sqlite—a CLI tool that can convert GeoJSON files (consisting of a Feature or a set of features in a FeatureCollection) into a table in a SQLite database. If you use the --spatialite option it will initalize the table with SpatiaLite and store the geometries in a spacially indexed geometry field—without that option it stores them as GeoJSON. # 31st January 2020, 6:40 am

2019

togeojson (via) Handy JavaScript library and command-mine tool for converting KML and GPX to GeoJSON, by Tom MacWright # 18th January 2019, 11:50 pm

2017

simonepri/geo-maps. Neat project which publishes GeoJSON maps of the world automatically derived from OpenStreetMap. Three variants are available: country political maritime boundaries, country political coastline boundaries and a general outline of the world’s land territories. # 21st November 2017, 4:06 pm

2010

Polymaps. Absurdly classy: “a JavaScript library for image- and vector-tiled maps using SVG”. It can pull in image tiles from sources such as OpenStreetMap, then overlay SVG paths specified using GeoJSON. The demos make use of GeoJSON tiles for US states and counties hosted on AppEngine. The library is developed by Stamen and SimpleGeo, and released under a BSD license. SVG support in the browser is required. # 20th August 2010, 6:46 pm