arthur-e

Managing the PostgreSQL Service

The service name is postgresql and it accepts the usual commands for a background service:

• start
• stop
• restart
• status

arthur-e

Installation

# Requires Node.js and NPM
sudo npm install -g topojson

# Install the geojson-cli
sudo npm install -g geojson

Tasks

arthur-e

/**
    Returns an object which can be used to calculate statistics on the
    the passed numeric Array.
 */
var Stats = function (arr) {
    arr = arr || [];

    // http://en.wikipedia.org/wiki/Mean#Arithmetic_mean_.28AM.29
    this.arithmeticMean = function () {
        var i, sum = 0;

arthur-e

Introduction

Drivers

These are the exact names that OGR recognizes; in parentheses are the file extensions, not to be included in the driver name:

• ESRI Shapefile (*.shp)
• KML (*.kml)
• AVCE00 (*.e00)
• AVCBin

arthur-e

import math

def tweensegs(longitude1, latitude1, longitude2, latitude2, num_of_segments):
    ptlon1 = longitude1
    ptlat1 = latitude1
    ptlon2 = longitude2
    ptlat2 = latitude2

    numberofsegments = num_of_segments
    onelessthansegments = numberofsegments - 1

arthur-e

# Credit goes to my colleague Tyler (http://tylerickson.blogspot.com/2011/09/installing-gdal-in-python-virtual.html)

ENVDIR=/usr/local/pythonenv/
ENVNAME=nasabaer-env
OWNER=arthur

# Install GEOS if necessary
# sudo apt-get libgeos-3.2.2 libgeos-dev

# Install GDAL on the system

arthur-e

Overview

In general, it seems there are roughly five (5) ways to get "file data" (e.g. a GeoTIFF) out of a PostGIS geoprocessing workflow:

• Export just the raster field as an ASCII grid
• Connect to the database using a desktop client (e.g. QGIS) [1]
• Use a procedural language (like PLPGSQL or PLPYthon) [2]
• Use the COPY declaration to get a hex dump out and convert it to a binary file
• Fill a 2D NumPy array with a byte array and serialize it to a binary file using GDAL or psycopg2 [3, 4]
• Use ST_AsTiff() or the more general ST_AsGDALRaster() to get a byte array, which can be written to a binary file

arthur-e

Apparently even a difference of the least precision of the upper left-hand corner causes an alignment error in PostGIS. Consider this example, where I am comparing a land cover raster subset by an MTBS raster and the MTBS raster itself (with the goal being to add the latter to the former, creating the "burned" land cover).

```
SELECT ST_MetaData(r1.rast)
  FROM
(SELECT rast
   FROM geowepp_burnedarea
  WHERE geowepp_burnedarea.rid = 2) r1
UNION
SELECT ST_MetaData(r2.rast)

arthur-e

# Clear out any old ppa's that might conflict
sudo rm /etc/apt/sources.list.d/*mapnik*
sudo rm /etc/apt/sources.list.d/*developmentseed*
sudo rm /etc/apt/sources.list.d/*chris-lea*

# Add new ppa's
echo 'yes' | sudo apt-add-repository ppa:chris-lea/node.js
echo 'yes' | sudo apt-add-repository ppa:mapnik/nightly-trunk

# Update