[talk-au] Geoscience NATMAP 250K Topo Maps

[mick]

On Wed, 20 Nov 2013 08:34:46 +1100
David Bannon <dbannon at internode.on.net> wrote:

> On Wed, 2013-11-13 at 19:13 +1100, Andrew Harvey wrote:
> > Just a heads up that GA have a tile service for their NATMAP 250K Topo
> Maps.
> > 
> 
> Thanks Andrew, I thought the list might be interested in a few comments
> about this service.
> 
> Firstly, really cool that they are doing it !
> 
> Putting aside the licensing issue, I am not sure how useful the data is
> wrt populating OSM. Its all pretty dated, I spotted a number of age
> related errors in just the areas I am familiar with. So, I'd suggest
> that armchair mappers could not use it to to update roads, park
> boundaries and things like that. 
> 
> On the other hand, it might be useful (licence permitting !) when
> working on geographical features that don't change much and are
> difficult to survey. Creek and river beds come to mind.
> 
> Lee was interested in historical location names from memory...
> 
Some gotchas I've found using the topo 250k combined with higher resolution subsets (e.g maps derived from the 10K & 50k sets) is that they are not consistant in the placement of objects, with variations of up to 300 metres. The completeness of labeling of objects also falls off as resolution reduces.

I have also noticed that projection seems to be inconsistant between sets.

These observations may well be my incompetence.

To gain some confidence in what I've collected I plan to drive as many roads in my area of interest (Glen Innes, NSW) several times with my two GPS units recording and find an acceptable level of coincidence before I add anything to OSM.

Mick aka 'sparrowhawk'