Working with Vector Data –The Basics - PostGIS - page 116

Working with GPS data
In this recipe, you will work with GPS data. This kind of data is typically saved in a
.gpx file.Youwillimportabunchof. gpx filestoPostGISfromRunKeeper,apopular
social network for runners.
If you have an account on RunKeeper, you can export your .gpx files and process
thembyfollowingtheinstructionsinthisrecipe.Otherwise,youcanusetheRunKeep-
er .gpx filesincludedinthe runkeeper-gpx.zip file,locatedinthe chp03 direct-
ory included in the code bundle available with this topic.
Youwillfirstcreatea bash scriptforimportingthe .gpx filestoaPostGIStable,using
ogr2ogr . After the import is completed, you will try to write a couple of SQL quer-
iesandtestsomeveryusefulfunctions,suchas ST_MakeLine togeneratepolylines
from point geometries, ST_Length to compute distance, and ST_Intersects to
perform a spatial join operation.
Getting ready
Extract the data/chp03/runkeeper-gpx.zip file to working/chp03/run-
keeper_gpx .Incaseyouhaven'tbeenthrough Chapter1 , Moving Data In and Out
of PostGIS , be sure to have the countries dataset in the PostGIS database.
How to do it...
First,besureoftheformatofthe .gpx filesthatyouneedtoimporttoPostGIS.Open
oneofthemandcheckthefilestructure—eachfilemustbeintheXMLformatcom-
posedofjustone <trk> elementthatcontainsjustone <trkseg> elementthatcon-
tainsmany <trkpt> elements(thepointsstoredfromtherunner'sGPSdevice).Im-
port these points to a PostGIS Point table.
1. Createanewschemanamed chp03 tostorethedataforalloftherecipesin
this chapter using the following command:
postgis_cookbook=# create schema chp03;