4. Convert GIS formats
4.3. Spatial queries of vector data
For our map of Delft
we want to do the following GIS analysis:
- Select the community of Delft
from the community map and save it into a new shapefile;
-
Intersect the community boundaries of Delft with
the road map of the Netherlands.
We can
use a spatial query to select a feature from a vector map.
1. What is the attribute in the community map containing the names of
the communities? You can use either ogrinfo or QGIS to answer this question.
2. Execute the following command:
ogr2ogr
-f "ESRI Shapefile" -where GM_NAAM='Delft'
-a_srs EPSG:28992 delft.shp gem_2011_gn1.shp
This
will save the feature with GM_NAAM
Delft to a new file called delft.shp. The
argument -a_srs EPSG:28992 is used to assign the Amersfoort/RD New projection
to the output file. The argument -f defines the output format.
3. Now open in QGIS the reprojected DEM (dem_rd.tif), the
reprojected road map (roadsreprojected.shp) and the community of Delft (delft.shp).