Help Wanted: QGIS Mentor



My goal was simple, generate a heat map in QGIS that looked similar to the heat map that I generated using Google Fusion Tables with just a couple of clicks, or similar to what was eventually implemented on Garmin Connect.

This is what my test data set of 350,000 GPS points looks like in QGIS 1.9.0 on a PostGIS layer:

PostGIS Layer in Quantum GIS 1.9.0

PostGIS Layer in Quantum GIS 1.9.0

Several attempts resulted in either no visible heat map (above) or a large blobbish, weather map looking effect, not what I wanted.

I talked to the cartographer who took my Google Fusion Table prototype from concept to production. His process bears little resemblances to my prototype. Instead of a loose collection of GPS points, he extracted running and cycling activity polylines. Instead of using a heat map plugin he wrote custom C++ code to convert the vector data into raster data.

So, I’ll switch from loose points to polylines too. Oracle Spatial and Graph has a SDO_UTIL.FROM_GML311GEOMETRY function to export the polylines in GML format. Likewise, PostGIS has a ST_GeomFromGML to import GML data into a geometry. I’ll work on creating a data set of 20,000 – 30,000 polylines.

I sure could use a QGIS mentor to answer my basic questions and to help me avoid making wrong turns. It might be time to reach out some cartographers in other departments at work.  I also plan on reading “Learning QGIS 2.0,” by Anita Grase, when that comes out later this month. I guess Anita can be my virtual mentor.