[talk-au] Increased precision options for Australia - QZSS, SBAS or Galileo

Leith Bade leith at bade.nz
Tue Jun 12 10:49:51 UTC 2018

The GA claim is bit exaggerated. An cell phone is unlikely to ever get 3cm
as you just can't build a good GPS antenna in the form factor. Future self
driving cars however will be designed to meet this specification with mass
market RTK receivers (think sub $100) and correctly integrated antennas. I
think it will be 5 or more years before cm level car positioning is common

Yes you can map to within 0.3cm, but what reference frame? E.g. the
Canberra imagery I've seen is in GDA94 which is ~1.8m away from the current
WGS84 reference frame. So I guess locally it might be accurate
street-to-street. But if you were to survey the road compared to data in
NSW it could all be shifted by a metres.

Leith Bade
leith at bade.nz

On 12 June 2018 at 20:29, Andrew Davidson <theswavu at gmail.com> wrote:

> On 12/06/18 20:04, Leith Bade wrote:
>> Our receivers work fine in Australia as I live in Canberra and work for
>> the Swift Navigation engineering department. Using one of the free CORS
>> stations here I can get 2cm positions from my car. Mind you the setup cost
>> ~$2000.
> This is the bit I'm a bit dubious about. The blurb on GA suggests that we
> are going to be getting 3cm accuracy from our smart phones, but I'm
> wondering how the development of GPS antennas small and cheap enough to go
> into phones is coming along.
> Unfortunately OpenStreetMaps only uses "WGS84" as it's datum which is not
>> that well defined compared to a surveying datum like GDA94/2020 or ITRF,
>> and most existing data has only been measured to a few metres (at most). So
>> I wouldn't worry too much about the drift as there are other larger sources
>> of error in OpenStreetMaps.
> Reminds me of a paper I read on the the subject where the author pointed
> out that anyone who says they are mapping to "WGS84" doesn't know what they
> are talking about. However, I do think you are being a little pessimistic.
> So long as there is good aerial photography or some external dataset
> available it's possible to get closer. In Canberra, provided that the
> mapper traces carefully, you can easily map things to within 0.3m.
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