Robinia pseudoacacia (Black locust, False acacia). There are several Mop Top Robinias in gardens adjacent to HWG and their offspring has been a nuisance in HGW
Hi Ruth Cameras take a while to link up to the satellites for the GPS. If they haven’t linked up properly then the location may be out by a few hundred metres or more. This seems to be what has happened. You have the status of Trusted Contributor. So you should be able to edit the sighting and adjust the location.
This is a bit difficult to distinguish from Gleditsia triacanthos (not included on CNM) at this stage. Robinia has pairs of broad spines and Gleditsia has narrower spines. Check sighting http://canberra.naturemapr.org/Community/Sightings/Details/3343560 which looks more like Gleditsia spikes.