Tags » PostGIS

How to correct a linestring for the antimeridian (180 longitude)

When making a GEOMETRY linestring that crosses the antimeridian, it is common to see a horizontal line across the map. This is because the GEOMETRY data type deals entirely in map units, so interprets the world as being flat. 208 more words


Airline route maps

Some airline route maps, showing the routes flown by each airline.

British Airways, whose flights remind me a bit of a daddy long legs. None of these maps show code shares, where you book with one airline, but are flown by a collaborator. 95 more words


How to make a great-circle linestring

The postGIS GEOGRAPHY type connects two points on the Earth’s surface by the shortest route (the great-circle line). Unfortunately when displayed in Quantum GIS, this will appear as the shortest route between two points in map-space (actually a… 47 more words


How to name your road

In Motorway or motornay? I coloured UK roads by the first number in their name. To make the nomenclature clearer I have grouped these roads into regions, then coloured the map below. 114 more words


KNN with FLANN and laspy, a starting place

FLANN is Fast Library for Approximate Nearest Neighbors, which is a purportedly wicked fast nearest neighbor library for comparing multi-dimensional points. I only say purportedly, as I haven’t verified, but I assume this to be quite true. 502 more words


Drivetime analyses, pgRouting

We’ve got some quick and dirty pgRouting-based code up on github. I say quick and dirty because it directly references the table names in both of the functions. 410 more words


Importing Large Spatial Datasets into PostGIS

Is PostgreSQL/PostGIS suitable for Big Data? This is a question I have been asking myself for a while, and I now have the opportunity to test it with a PostgreSQL instance from Amazon Web Services (AWS); after all, if such a service… 1,015 more words