Archive for the 'linux' Category

Using OGR to convert GIS Vector formats

Published by Jonah on July 18, 2008 in geospatial, gis, linux and oss. 1 Comment

OGR is a part of GDAL and is very useful for converting between geospatial vector formats. What does that mean? When storing Vector GIS data there are a dizzying number of formats it can be stored in, some of the more popular of late, or at least well known are KML and SHP. A friend of a friend was looking to convert some SHP (Shapefiles) into KML so that he could make a Google Maps mashup and I helped him out. Here is a workflow for how I went about performing the conversion.

OGR can be installed on debian/ubuntu machines by installing the package gdal-bin:

sudo apt-get install gdal-bin

Once you have GDAL/OGR installed you get a slew of command line utilities, I’ll try to cover some others in later tutorials, but for now we’re interested in ogr2ogr. ogr2ogr converts between the vector formats that OGR understands.

Example using a shapefile at the city of chicago website:
Download the data

wget http://egov.cityofchicago.org/webportal/COCWebPortal/COC_ATTACH/TIFS2008.zip

Unzip it

unzip TIFS2008.zip

Now we have to do the hard part (not really that hard, but important), look for the projection information in the metadata. I looked in the tifs.shp.xml file and found that the projections is:

NAD_1983_StatePlane_Illinois_East_FIPS_1201_Feet

Google uses WGS84 spatial reference system.
Now we have to lookup EPSG codes that OGR understands for these projections. A good spot to do this is spatialreference.org. EPSG codes provide a short form of expressing projection and spatial reference information.
Once we have that all sorted out we’re ready to run ogr2ogr:

ogr2ogr -f "KML" -s_srs "EPSG:102671" -t_srs "EPSG:4326" tifs.kml tifs.shp

The -f “KML” specifies that we want the output in KML. -s_srs is the source (tifs.shp) spatial reference system and -t_srs is the target spatial reference system found at spatialreference.org, then we specify the output file tifs.kml and the input file tifs.shp. That is it!

Lets shrink it down into a kmz (compressed kml) so that it takes up less disk space.

zip tifs.kmz tifs.kml

Scanning with sane’s scanimage from an ADF scanner to PDF and OCRed Text

Published by Jonah on January 5, 2008 in Uncategorized, hacks, linux, scanning, software and ubuntu. 4 Comments

Using libsane and tesseract, you can scan from an ADF (or non ADF) scanner in Ubuntu 7.10 to a PDF and OCR’ed text document with a few easy steps.

First we need to make sure we have the necessary packages installed.

apt-get install tesseract-ocr sane-utils

Continue reading ‘Scanning with sane’s scanimage from an ADF scanner to PDF and OCRed Text’

ntfsundelete

Published by Jonah on December 20, 2007 in linux and software. 0 Comments

Just did a stupid thing and deleted a whole tree of file on a windows partition. Never fear…ntfsundelete is here.

sudo ntfsundelete -u -d /destination/directory -f -m *.jpg /dev/sda1

Run without the -u option and -d options to show what can be recovered.

On ubuntu/debian to install it do:

apt-get install ntfsprogs

Getting to know PostGIS

Published by Jonah on November 6, 2007 in database, geospatial, gis, linux, software and ubuntu. 3 Comments

I am making the plunge to get more informed with how to use PostGIS. It is pretty impressive so far. Here is a quick tutorial which shows you how to get started and loading in a shapefile to play around with some fun SQL querying. I assume a basic understanding of the linux command line and some basic SQL skills.

To get started in ubuntu 7.04 (should work in 7.10 and debian too):

$ sudo apt-get install postgis postgresql-8.1-postgis

Next we’ll start setting up the PostGIS environment.
Continue reading ‘Getting to know PostGIS’

Synergy

Published by Jonah on March 2, 2007 in linux, oss and software. 0 Comments

Synergy is a network KVM. It is great if you have multiple computers. I have a setup with a Powerbook, WinXP and Ubuntu Laptop all controlled by the same keyboard and mouse (across four screens) merged together into one desktop. It is a beautiful thing… Some simple config examples after the jump.

Continue reading ‘Synergy’