[MLB-WIRELESS] New Node Coordinates?

[Tim Hogard]

> Ian Donaldson wrote:
> 
> | Nick, you are most welcome. I haven't even gone into the whole datum
> thing
> | which are different 'models' of the world and give different
> co-ordinates.
> | I think melbwireless unofficially uses AGD66 which is what Melways and
> | VicMap also use but I don't think its stated anywhere.
> 
> As far as I know, this sounds correct. However, given that I was the
> main contributor to our mapping software, you should all be scared by
> that statement :P
Most of the melways seems to be AGD but my GPS gives WGS84 by default
and it appears that the outer maps of Melways is WGS84.

At least it isn't the Kiwi-Datum-200? which is the 1st datum based
on the fact that some parts of the country are moving at nearly 1m
a year away from other bits.  The problem is that one of the base
stations they used to measure that moved about 10m in about a week.

For thouse that are going "what the **** is a map datum?"....
Everyone should know that coordinates are based on the equator and
Greenwich.  The problem is that now we can tell where the observatory
at Greenwcih is within about .001 meters how do you figure the
absolute coordnates of some point.  Thats what map datum are all
about.  150 years ago theMelbourne datum would have been based on
some point at the local observatory.  In 1966, it was based on a
few things that wer a bit off.  Now with WGS84, things are better
for some reason everthing is moving faster than WGS84 can cope with.

And your GPS can't cope with the modern kiwi datum even when the hills
aren't going for a walkabout.

-tim
http://web.abnormal.com

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