[clug] GPS, GIS, GTS, SDI and FOSS

Jim Croft jim.croft at gmail.com
Wed Mar 2 16:49:19 MST 2011

Well it turns out that we (ANBG) do have a CORS subscription using the
Dickson base station and have been able to get accuracy on Black
Mountain of c. 10- 20 cm, which is good enough for our purposes (where
plants 'n stuff are).  Using post processing or in real time.
Apparently it cost us c. $ 2k for the subscription.


On Thu, Mar 3, 2011 at 10:34 AM, Scott Ferguson
<scott.ferguson.clug at gmail.com> wrote:
> On 03/03/11 07:21, Brad Hards wrote:
>> On Thursday, March 03, 2011 12:27:51 am Scott Ferguson wrote:
>>> * Another solution to ionospheric distortion is internet sourced
>>> corrective data - any suggestions/experience there?
>>> A local base station is unlikely to work due to the local topography.
>> I wouldn't have expected that there would be much variation in ionospheric
>> delay across the ACT (or anywhere roughly north / south). The variation is
>> strongest at dawn / dusk. Can you just put something on the roof?
>> Brad
> Even that tiny variation adds significant error. The best non-military
> GPS systems on the market cannot achieve less than 10m absolute accuracy
> without corrective data. I can't quickly locate the figures - but after
> local signal reflections the largest error factor is ionospheric
> distortion (40%?). Of course the DSE sales rep will disagree with me... :-)
> I was probably (late night post) a little unclear - my requirements are
> for reproducible 1/2 meter to 1 metre absolute accuracy in the ACT with
> sub-2 minute warm starts at less than $1K per unit.
> http://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Atmospheric_effects
> Not sure what you mean by "put something on the roof"... antennae?  If
> so it is a means of reducing signal reflection - doesn't correct for
> lens effects.
> I'm happy to discuss this further, time allowing, especially as it is a
> learning curve for me, but probably best either off-list or under an
> [OT] prefaced subject-line (lest I become a hypocrite!)
> Cheers
> --
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Jim Croft ~ jim.croft at gmail.com ~ +61-2-62509499 ~ http://about.me/jrc
'A civilized society is one which tolerates eccentricity to the point
of doubtful sanity.'
 - Robert Frost, poet (1874-1963)

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