In February Jamesgeo Team NZ flew on Air Safaris’ Grand Traverse and took lots of photos. For the record, this was an excellent experience. The Air Safaris guide shows the proposed flight path… but where did we really fly?
Step 1: Georectify image
I have used QuantumGIS’s georeferencer plugin to turn the above image into a map by identifying a number of Ground Control Points (GCPs), such as Lake Tekapo airport, Glentanner Park and various road junctions. This results in a georectified (and georeferenced) image, displayed in WGS84, the coordinate reference system of the GPS points used as the GCPs.
I made a new postgreSQL table with columns for both 2D and 3D geometries, then inserted each point (see bottom of page for SQL commands). This gives us 1410 points, coloured here by altitude. I have reprojected the map into the New Zealand map grid (EPSG:27200).
Step 3: Compare these points with the guide
Displaying this route on top of the Air Safaris map:
So our blue track is pretty close to the advertised red track. Well done Air Safaris!
To create the postgreSQL table:
CREATE TABLE nz.scenicflight
gid serial NOT NULL,
dt timestamp without time zone,
elev double precision,
To insert each data point:
INSERT INTO nz.scenicflight (dt, elev, geom, geom3d) VALUES (‘2015-03-29T14:16:12Z’, 763.9, st_geomfromtext(‘POINT(170.4411594 -44.00242729)’, 4326), st_geomfromtext(‘POINT(170.4411594 -44.00242729 763.9)’, 4326));