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Topology of Hex Cells

A year ago I had modified code from here to make a set of about thirty million hex cells across the continental United States, using the projection from the National Map, EPSG:2163. Today, topology wizard strk was building a set of hex cells to test conversion to topology in PostGIS 2.0. The question arose, would […]

PostGIS Geocoder behavior

I became interested in the practical behavior of the     PostGIS TIGER 2010 Geocoder when I started doing statistical profiling of the results of geocoding 100,000 standard addresses in my county and got results that looked like what you see in the image at right. That inquiry morphed into this short paper PDF. Why statistical profiling? […]

ST_DWithin on a Grid

As part of a larger inquiry, I wanted to know how ST_DWithin() behaved on a regular grid – that is, what is the relationship of the input radius, and the number of grid cells that could be selected in the result. The manual implies that it is an intersects relationship not a contains relationship, and […]

California in Green and Rust

I set out to create a map that showed urban sprawl in the central valley of California. Geoserver, OpenLayers and PostGIS are the technologies in this demo. (the linux server itself is being relocated) Introductory Overview An overview of the central valley from a natural perspective, overlaid with two prominent marks of human development, highways […]