Using OpenStreetMap Data - P.2

Lets talk about QGIS for a lit­tle bit before we go ahead and install it on our sys­tems. QGIS is an open source GIS pack­age that is under the GNU pub­lic license. It offers enough func­tion­al­ity for some­one with a ArcInfo Stu­dent License (myself) to want to explore. The usage of QGIS in day to day tasks has me spend­ing less time scratch­ing my head about why some­thing has crashed (ArcMap any­one?) nor am I sit­ting here wait­ing for hours on end while the geo­pro­cess­ing occurs (on and on and on), and ulti­mately fail­ing to com­plete. OK ArcMap isn’t so bad! I just love the idea of a com­mu­nity dri­ven GIS project. Even more-so, I love the fact that I can run it on my Mac­book Pro with­out hav­ing to load MS Win­dows. It is at a point in its life where it has matured and is ready to be used in pro­duc­tion. With its vast sup­port for almost every file­type (vec­tor or raster), as well as func­tion­al­ity with Post­GIS and other data­bases, it is def­i­nitely a uni­ver­sal GIS. Put it this way, if this is your first time using QGIS, you will be adding just another tool to your geospa­tial arsenal!

Installing QGIS and its dependencies

The QGIS depen­den­cies and the QGIS installer are located on the Kyn­gChaos Wiki.

• nav­i­gate to http://www.kyngchaos.com/software/qgis
• down­load the ‘GDAL Com­plete 1.8 frame­work pack­age’ to your ‘/Desktop/osm_tutorial/downloads’ folder
• down­load the appro­pri­ate ‘GSL frame­work’ to your ‘/Desktop/osm_tutorial/downloads’ folder
• down­load the appro­pri­ate ‘QGIS 1.7.x.x’ build to your ‘/Desktop/osm_tutorial/downloads’ folder
• pro­ceed through the instal­la­tions of GDAL and GSL before QGIS. Make sure to accept all the default configurations/options.
• QGIS instal­la­tion is also straight for­ward, install this after GDAL and GSL

Querying PostGIS inside QGIS

Lets launch QGIS for the first time and query our PostgreSQL/PostGIS data­base and load some Open­StreetMap data.

• launch QGIS from the appli­ca­tions folder
• ‘file > save project as’ and save the project before we get started and for­get to!! Name it some­thing relavent and place it in the ‘/Desktop/osm_tutorial/data’ folder
• the tool­bar at the top of the appli­ca­tion win­dow holds the tools that allow us to add new data to our map
• by hov­er­ing over the icons we can locate the “Add Post­GIS Layer” tool. Select this tool to open the Add Post­GIS Tables dialogue
• select ‘new’ to add our Post­GIS database
• con­fig­ure your new Post­GIS layer as so (remem­ber that the Post­GIS layer uses your Post­greSQL con­fig­ured user­name and password):

If this works you will be able to con­nect to your Open­StreetMap Post­GIS layer and you will get the fol­low­ing screen

I will show you how to add some data using the query builder. All that you will need to do is get a grasp of the query builder syn­tax and the OSM tables so you can build your own cus­tom queries and add OSM data to your projects at your hearts content.

• select the first row, ‘public|planet_osm_line|LINESTRING|way’
• select ‘Build Query’
• using the inter­ac­tive query builder, repli­cate the fol­low­ing query syntax:

*Tip* select ‘all’ in the ‘Val­ues’ col­umn to see all the avail­able headings

• choose ‘OK’
• select ‘Add’

The data will be queried from your PostgreSQL/PostGIS data­base and added to your map. If you have fol­lowed the tuto­r­ial using the Ontario extract you should have some­thing that looks sim­i­lar to this:

That is it! You are now ready to start using OSM data in your GIS. Note that you can export to shape­file in QGIS so that you can take the data and move it across com­put­ers and open it up in other GIS appli­ca­tions (*cough* ArcMap *cough*). Remem­ber to save often incase QGIS crashes. I would hate to have lost some lengthy queries because of a crash… some­times try­ing to remem­ber exactly what I included in a query is the hard­est part of the project I am work­ing on!

If you have enjoyed this tuto­r­ial or if it has helped you to some extent please share your expe­ri­ence below!

Any sug­ges­tions or rec­om­men­da­tions? I would love to hear from you as well.

Cheers!