Paul’s Blog

A blog without a good name

Golf From the Air

Rweait’s post on golf courses got me thinking about mapping some myself, but by aerial photos. To start with, I selected a golf course near the Serpentine River in Surrey, BC.

Opening up this area in JOSM reveals that the golf course was mapped as a multipolygon, essentially entirely by me. The source tags also tell me that the water was imported from Surrey GIS data and the other features are from 2010 aerial photos. Of course, I already knew this, but it’s good to check if anyone has come along and mapped more updated info.

Looking at the orthos, I can quickly see that all the water present is accurately mapped, and what exists agrees with the photos, with the exception of one stream. I also know from experience with this imagery that I do not need to apply an offset as it is already correctly aligned.

The one stream that stands out is an import from the NHN database, which often contains outdated ditch information in agricultural areas. What is likely is that this golf course was once farmland and contained a ditch that followed that alignment. Regardless, knowing how it got there and that my imagery is more accurate and up to date, I go ahead and remove it.

The first tracing to do is the paths. highway=track is what is currently used and seems sensible, as well as agreeing with a wiki proposal. The tag information tools wouldn’t be very helpful here, they would just tell me there are lots of tracks and paths world-wide.

Tracing this many tracks takes awhile, but once it’s done the course is starting to take shape. This step added about 1300 nodes, including adding some buildings and parking lots in the normal way.

Looking at one of the simpler holes, the one to the north-east corner of the course, I can see that putting greens are the lighest color in the 2010 orthographs, the long fairways are a medium color, and the tee areas are the darkest green. The bunkers are very obvious, being sand. But how to tag these? Rweait’s post, taginfo, and the wiki all agree on bunker, tee, green and fairway, with the additional value of golf=hole for the holes themselves.