Buffers, cost surfaces, least cost path with OSM

buffers_cost_osm.rst

Geospatial Analysis II: buffers, cost surfaces, least cost path

http://courses.ncsu.edu/gis582/common/grass/buffers_cost.html

Tested with QGIS 2.4 and GRASS GIS 7.0.

Download the OpenStreetMap data in QGIS

Start QGIS.

Plugins > Manage and install

Install GRASS plugin.

Plugins > GRASS > Add GRASS raster layer

Select GRASS database directory with the NC SPM sample Location (probably grassdata in your user home directory or in documents directory). Select nc_spm_08 for Location (or whatever is the name of NC SPM Location you downloaded) and Mapset PERMANENT.

Vector > OpenStreeMap > Download data
Extent: From layer: elevation
Output file: raleigh.osm in Downloads, Documents or in gisdata directory
OK (and wait)
Close the dialog when import is finished

Vector > OpenStreeMap > Import topology from XML
Set Input XML file to `.osm` file downloaded in the previous step
OK
Close the dialog when import is finished

Vector > OpenStreeMap > Import topology from XML
Set Input XML file to `.osm.db` file downloaded in the previous step (`raleigh.osm.db`)
Export type: Polylines
Output layer name: raleigh_osm_roads
In Exported tags, click Load from DB
Select tags: highway, name, oneway, lanes, maxspeed, ref, proposed
OK
Close the dialog when import is finished

Right click on the roads layer and select `Save as`
Choose a filename
CRS: Project CRS
Save

In GRASS GIS, Search module > Import, export and link data > Import vector data > Common import formats (TODO: the string should be changed in GRASS to Common formats). Select the exported file and import.

Additional materials about OpenStreetMap and QGIS

• http://learnosm.org/en/osm-data/osm-in-qgis/
• http://wiki.openstreetmap.org/wiki/QGIS
• http://wiki.openstreetmap.org/wiki/Highways
• http://docs.qgis.org/2.2/en/docs/user_manual/osm/openstreetmap.html

Cost surfaces Compute cumulative cost surface to a given accident site based on speed limits