Greetings. In Gang-gang, May 2007, there was an announcement from COG's
Records Management Sub-committee about a formal decision on map datums
for us to use, as follows:
Notice to all contributors to the COG database: A change
to the recommended map datum.
Until recently the maps produced in Australia have used a local map
datum known as Aus Geod 66. This has now changed to an international
map datum known as GDA or WGS 84. Google Earth is set to WGS 84 as are
all GPS units although in the latter case the datum can be changed. The
consequence of this change is that a geo-coordinate will mark a
different spot on a map depending on the datum used. For instance, a
location marked with a the WGS 84 datum will be approximately 218
meters to the north-east of a location marked with the Aus Geod 66
datum. After consideration by the Records Management Sub-committee, the
COG Committee has decided to change the default map datum from Aus Geod
66 to GDA or WGS84 and the standard geo-coordinates to
Latitude/Longitude degrees, minutes and seconds (hdddo mm’ ss.s”). It
will no longer be possible to record geo-coordinates as Universal
Transverse Mecator (UTM). The COG data entry sheet, the on-line data
sheet and the base maps published on the Web and in the ABR will be
changed as soon as possible after 1 July to reflect these changes.
Please note it is important to know the datum of any maps that are
being used to determine locations. It is possible that many of the maps
used by members are based on the old datum of Aus Geod 66. If there is
no reference to the datum on the map then it will be based on the old
datum. For those using GPS units the datum will need to be checked and
changed to WGS84 or GDA and the geo-coordinates changed to hdddo mm’
ss.s” if necessary. If connected to the Internet then the appropriate
coordinates of your location can easily be determined using Google
Earth. For any points of clarification please contact Chris Davey on
62546324 (h), email m("aapt.net.au","chris_davey");">.
Regards - David
Paul Fennell wrote:
Paul
Sounds like a good idea to me. I am not familiar with KML format, but am
interested to know what the final product will look like, and how we would
use it.
I assume you would be using the WGS84 projection. This would give a final
map slightly different from those maps prepared by Malcolm Fyfe which COG
members now use, because they were based on AGD. As I understand it the
grids would move about 80 metres to the southwest. Or put another way, the
points on the map would move 80 metres to the northeast relative to the old
grids.
This may or may not cause some problems with Grid References. The main hot
spot would be I think the Sewage Treatment Ponds which would appear to move
from L14 to M14.
Anyway, COG has to bite the bullet about new maps some time. Your approach
may precipitate a bit of policy reconsideration.
All the best with your project.
Cheers
Paul
Paul Fennell
COG Database Manager
02 6254 1804
0407 105 460
-----Original Message-----
From: m("ozemail.com.au","birder");"> [m("ozemail.com.au","birder");">]
Sent: Thursday, 17 July 2008 5:13 PM
To: m("canberrabirds.org.au","canberrabirds");">
Subject: Grid for Newline Paddock
On Thu, Jul 17, 2008 at 04:10:46PM +1000, Paul Fennell wrote:
Comments anyone? Maybe someone can knock up a map?
I'm working on a COG grid overlay in KML format for Google Earth;
I'll make it available once it is complete. The basic grid is
laid out, but need to rename the grid squares to match the COG
naming system and do a little fine tuning.
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