Google Earth map overlays for Wee Jasper (Dip Series) and Bungonia caves

[Ben Low]

Attached are two Google Earth overlays, one of Dip Series at Wee Jasper and the other the surface map of Bungonia. If you open these in Google Earth you should be able to zoom in to WJ and Bungonia and get a plan view showing WJ Dip Series and the Bungonia surface map. The latter, in particular, may be helpful in using the 'Under Bungonia' maps with modern (correct) topo maps and GPS.

The Dip Series cave map is from the book "Wee Jasper Caves" (Dunkley, Spate, Wells), which in turn seem to be from Helictite 02.02 1964 (Jennings). The overlay scale and orientation was by eye and the Google Earth measurement tool. The map doesn't quite match up with GPS waypoints, presumably due to both GPS and 1950's cartography errors; so accurate give or take a few meters.

The Bungonia Caves surface map is from 'Under Bungonia' (J&P Baur), 1998. The surface map is incorrectly labelled as True North when in fact it was drawn to Magnetic North (ref. p 141 of Under Bungonia). The map grid is also unconventionally drawn aligned to Magnetic North, not the usual Grid North. The 'magnetic north' grid lines get in the way in the Google Earth overlay, so I (mostly) removed them. (This unconventional grid also explains why I've never been able to reconcile the UB grid refs with the Caoura 1:25k topo map and my own gps recordings).

Speaking of to map errors: I compared some landmarks (Ranger station, Lookdown, Fossil Cave, Grill Cave) between aerial imagery, the Under Bungonia sketch map, and NSW Govt Land and Property Information SIX database, and with GPS waypoints recorded myself. I found that the SIX database seems to have some caves mislabelled, e.g. they have Kellys Cave where Fossil Cave is, and Fossil where Hogan's is, and Hogan's where Shaduf is; the others seem ok. I also note the SIX map shows the two Permanent Survey Marks near the ranger station as being some 150m NE of where the UB surface map places them; UB mentions on p. 143 that the data for these markers were "difficult" to obtain and was taken from a 1970 reference. So either SIX is incorrect (unlikely) the markers were moved between 1970 and 1995 (also unlikely) or the 1970's map and thus UB surface map is incorrect.

Anyhow, I've aligned the UB surface map to magnetic north (+12.5deg rotation in 1997) and scaled it by eye going by the aerial view (i.e. aligning the roads, the ranger station, the campsite and lookouts). The results seem to agree within 5-10 metres with a handful of GPS markers I've recorded in the area over the last year or so.

Yours in Scouting,

Ben Low

Venturer Leader
1st Balgownie Scout Group
0407 17 25 21
ben...@balgowniescouts.org.au