SpatiaLite: A Spatial Extension to SQLite

• timezones-api

  0 25 0.0 HTML

  A Datasette-powered API for finding the time zone for a latitude/longitude point

  It had been quite a while since a major release, but then SpatiaLite 5.0 came out a couple of months ago with some very significant new features - the K-Nearest-Neighbor stuff is particularly interesting. https://www.gaia-gis.it/fossil/libspatialite/wiki?name=5.0.0...

  I've built a few fun demos using SpatiaLite and Datasette. Here's an API that tells you the timezone for a latitude longitude point:

  https://timezones-api.datasette.io/timezones/by_point?longit... - implementation here: https://github.com/simonw/timezones-api

  And here's the same thing for which US county a point is within: https://us-counties.datasette.io/counties/county_for_latitud... - implementation here: https://github.com/simonw/us-counties-datasette

  I've also built an experimental Datasette plugin that lets you draw a shape on a Leaflet map to generate a GeoJSON polygon, then uses SpatiaLite to show you geometries that are contained by that drawn polygon. I wrote about that here: https://simonwillison.net/2021/Jan/24/drawing-shapes-spatial...

• us-counties-datasette

  0 9 0.0 Shell

  A Datasette instance exposing names, FIPS codes and polygons of US counties

  It had been quite a while since a major release, but then SpatiaLite 5.0 came out a couple of months ago with some very significant new features - the K-Nearest-Neighbor stuff is particularly interesting. https://www.gaia-gis.it/fossil/libspatialite/wiki?name=5.0.0...

  I've built a few fun demos using SpatiaLite and Datasette. Here's an API that tells you the timezone for a latitude longitude point:

  https://timezones-api.datasette.io/timezones/by_point?longit... - implementation here: https://github.com/simonw/timezones-api

  And here's the same thing for which US county a point is within: https://us-counties.datasette.io/counties/county_for_latitud... - implementation here: https://github.com/simonw/us-counties-datasette

  I've also built an experimental Datasette plugin that lets you draw a shape on a Leaflet map to generate a GeoJSON polygon, then uses SpatiaLite to show you geometries that are contained by that drawn polygon. I wrote about that here: https://simonwillison.net/2021/Jan/24/drawing-shapes-spatial...

• Appwrite

  appwrite.io

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  Appwrite - The Open Source Firebase alternative introduces iOS support. Appwrite is an open source backend server that helps you build native iOS applications much faster with realtime APIs for authentication, databases, files storage, cloud functions and much more!

  

• OfflineReverseGeocode

  0 470 0.0 Java

  Perform reverse geocoding locally and offline

  A kd-tree is the generalized data structure that can do log(n) lookups of nearest in any dimensions. I wrote an implementation for nearest to a geographical point years ago (since ported to many other languages): https://github.com/AReallyGoodName/OfflineReverseGeocode

  A less generalized solution is to grid things up (quad tree and bsp trees) as you implied above but the kd-tree is the generalized solution without edge cases (what if the majority of points of interest end up in a single grid square in your example?). A kd-tree is essentially what a sort list is for one dimensional data but instead supports multiple dimensions.

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