Boston GIS Articles and Tutorials

Part 1: Getting Started With PostGIS: An almost Idiot's Guide

Paragon Corporation (mailto:support@paragoncorporation.com) — 2015-10-12

What Is PostGIS?

PostGIS is an open source, freely available, and fairly OGC compliant spatial database extender for the PostgreSQL Database Management System. In a nutshell it adds spatial functions such as distance, area, union, int

pgRouting: Loading OpenStreetMap with Osm2Po and route querying

Paragon Corporation (mailto:support@paragoncorporation.com) — 2013-04-11

For this exercise we are going to demonstrate how to use OSM2PO and an OSM pbf to create a routing network. Much of this is borrowed from Anita Graser's tutorial O

Part 1: Getting Started With PostGIS: An almost Idiot's Guide (PostGIS 2.0)

Paragon Corporation (mailto:support@paragoncorporation.com) — 2012-05-12

What Is PostGIS?

Part 3: Using your own custom built OSM tiles in OpenLayers

Paragon Corporation (mailto:support@paragoncorporation.com) — 2011-06-19

In this third Part of our OpenStreetMap series we will demonstrate how to use the osm tiles we built in Part 2: Building Tiles with PostGIS OpenStreetMap data.

Part 2: Building Tiles with PostGIS OpenStreetMap data and Mapnik: Your Own OpenStreetMap

Paragon Corporation (mailto:support@paragoncorporation.com) — 2011-05-19

This is a continuation of our Loading OpenStreetMap data in PostGIS. In this tutorial we will build a tile cache of the Massachusetts data we loaded in Part 1 and then

Part 1: Loading OpenStreetMap data into PostGIS: An Almost Idiot's Guide

Paragon Corporation (mailto:support@paragoncorporation.com) — 2011-05-15

For this exercise, we will download Massachusetts OSM data and then load it into our PostGIS spatially enabled PostgreSQL database. The OSM data contains roads, points of interests, building footprints, administrative boundaries, addresses, and too man

PostGIS Concave Hull

Paragon Corporation (mailto:support@paragoncorporation.com) — 2010-06-04

This is a work in progress, and demonstrates the ST_ConcaveHull function that will be available in PostGIS 2.0. The basic approach is that it first creates a convexhull of the geometry and then uses the ST_Clo

OSCON 2009: Tips and Tricks for Writing PostGIS Spatial Queries

Paragon Corporation (mailto:support@paragoncorporation.com) — 2009-07-30

We gave a presentation on writing PostGIS spatial queries at OSCon 2009 last week. Slides will be available on the site, but you can download them

PostGIS ST_Dump, Dump

Paragon Corporation (mailto:support@paragoncorporation.com) — 2008-06-23

What is ST_Dump, Dump

ST_Dump is a function that takes a geometry and returns a set of Postgis geometry_dump structure. Geometry_dump is composed of 2 properties. geom and path. The geom is a geometry and path is a mu

PLR Part 3: PL/R and Geospatial Data Abstraction Library (GDAL) RGDAL

Paragon Corporation (mailto:support@paragoncorporation.com) — 2008-03-14

What is GDAL and RGDAL?

GDAL stands for Geospatial Data Abstraction Library and is a popular open source GIS library originally developed and maintained by Frank Warmerdam with contributions

PostGIS: ST_Translate

Paragon Corporation (mailto:support@paragoncorporation.com) — 2007-10-16

ST_Translate, Translate

The ST_Translate function takes any geometry (linestring, multiline etc) returns a new geometry that is the original geometry moved by a vector defined by X,Y,Z. Note the units of measurement are always in the units

Intersects Intersection: PostGIS - ST_Intersects, ST_Intersection

Paragon Corporation (mailto:support@paragoncorporation.com) — 2007-09-21

ST_Intersects, Intersects

ST_Intersects is a function that takes two geometries and returns true if any part of those geometries is shared between the 2. In PostGIS versions before 1.3 you would use the following syntax to utilize indexes <

Summary (pre 1.3.1 name), ST_Summary (+1.3.1)

Paragon Corporation (mailto:support@paragoncorporation.com) — 2007-08-24

ST_Summary(geometry) gives you a brief summary of a geometry telling you how many simple geometries, rings and type of geometry it is.


select ST_Summary(the_geom) from neighborhoods;

Output of the above ran from psql looks like

PostGIS Nearest Neighbor: A Generic Solution - Much Faster than Previous Solution

Paragon Corporation (mailto:support@paragoncorporation.com) — 2007-08-01

A generic solution to PostGIS nearest neighbor

After some heavy brainstorming, I have come up with a faster and more generic solution to calculating nearest neighbors than my previous solutions. For the gory details on how I arrived at this s

Solving the Nearest Neighbor Problem in PostGIS

Paragon Corporation (mailto:support@paragoncorporation.com) — 2007-07-21

A common problem encountered in GIS is the Nearest Neighbor problem. In a nutshell the problem is to find the x number of nearest neighbors given a geometry and n geometries of data.

The nearest neighbor crops up in other disciplines as wel