Satellite Differential GPS

[Bonus]

Howdy all, I have looked on the internet and there apparently is SDGPS in Australia. Can anyone give me some info on the system in Australia?
Thanks Russ

[25_ponies]

Russ,

Satellite based augmentation systems such as WAAS and EGNOS aren't available in Australia, so I don't think there's such as thing as Satellite Differential GPS in Aus.

There is an LF ground based augmentation system which offers DGPS in Australia, run by AMSA:- http://www.amsa.gov.au/Shipping_Safety/Navigation_Safety/Differential_Global_Postitioning_System/DGPS_Fact_Sheet.asp

Unless you really need the accuracy, the cost of the differential GPS and receiver is going to be quite prohibitive. Unless normal GPS units which are consumer goods, differential GPS kits are quite specialised and therefore very expensive. Having a look at a couple of sites around the place (eg - http://www.ja-gps.com.au/dgpsprod_csi_backpack1.html), looks like you are up for a starting price of around $2K for the receiver alone.

Hope this helps.

Alan.

[Bonus]

Thanks Alan for your info. I have a Raymarine 435 chartplotter and it has GPS status settings of SDGPS enable or SDGPS disable. When SDGPS is not available the unit fixes on anything that is available - I gather. I have tested it out and it does not seem to make a great deal of difference to fix strength when you try one or the other, but it may use more power if enabled as it is continually searching for what is not there. Does anyone have any thoughts on this.

[KAGEY1]

Diff Gps Was Designed To Take Out The Inaccuracy Of Standard Gps By Letting It Fix A Ground Base Station. Since The Us Has Increased The Accuracy Of The Normal Satellites, It Seems Superfluous To Me To Have It. During The Gulf War, They Deliberately Dialled In Discrepancies So As To Limit The Usefullness Of The System To The Enemy.they Had The Software To Eliminate These Discrepancies. Most Units Today Can Get A 3d Fix As Close As 5m. Good Enough For This Little Black Duck.
Cheers, Geoff

[Simmo2]

I think some radio stations could be potentially, or are used as beacons. This I think removes the 'second receiver' scenario. However the soft/hardware for this is dear.
I remember down at Kurramine Beach, comparing gps pozzies with a surveyer.... I was pretty much spot on with my Garmin....but then he said 'right. put it on paper, and mark the boundaries!' I was out by metres! His GPS was $25k?, mine was a grand!
I agree with the post by Kagey, the yanks can change the goal post position at will, but generally nowadays, the mark you hit last week will be within a cooee when you visit it again.

Hey, the yanks could put a missile through a window in a building via gps....the technology is there!! We just aren't allowed to use it to its potential...even if we could afford it!

[SatNav]

1. There is no SDGPS (such as WAAS. EGNOS etc) available in Australia

2. SDGPS (such as WAAS, MSAS, EGNOS etc) if activated in Australia will degrade accuracy not improve it

3. Differential is available in Australia but most recreational users do not require the added integrity

4. Hardware for AMSA type differential is quite inexpensive and most GPS receivers are differential ready. Many manufacturers no longer produce DGPS beacons although most of the world outside the USA have the system to use it.

5. Subscription GPS augmentation services are available but well beyond the normal user's requirements (and budget ~ $2000-$4000 PER year)

6. SDGPS will certainly degrade accuracy if enabled

7. SDGPS should be disabled on all receivers in Australia but unfortuneately some models do not allow this to be done

8. The US has NOT effectively increased the accuracy of GPS satellites apart from the normal upgrade program and discontinuing Selective Availability

9. The US did NOT "During The Gulf War, Deliberately Dial In Discrepancies So As To Limit The Usefullness Of The System To The Enemy" This thinking that the US deliberately altered the accuracy of the system is totally and completely incorrect.

10. There is now very little difference between military and civil GPS accuracy and any gap that does now exist will close even closer in due course.

11. New civil GPS accuracy specifications are being written as we speak and will be available around April 2008

12. The US has never used Selective Availability since it was terminated in May 2000 and next generation satellites will not even be fitted with Selective Availability hardware. Hopefully this will end selective Availability excuses in due course.

13. GPS alone is not used to put missles through windows and the real difference between military and civil GPs accuracy is not as much as some people would like to believe.

14. SDGPS in Australia? Turn it OFF

[Simmo2]

9. The US did NOT "During The Gulf War, Deliberately Dial In Discrepancies So As To Limit The Usefullness Of The System To The Enemy" This thinking that the US deliberately altered the accuracy of the system is totally and completely incorrect.



Prove it.....

[SatNav]

Prove it.....

1. During the gulf war GPS had not reached any stage of being declared operational with a limited number of satellites in orbit and the requirement to use civilian handsets as there simply were not enough military units to meet the demand

2. Selective Availability was in fact turned off during the gulf war for the main reason of being able to use civil receivers

3. Selective Availability was re-implemented on November 15, 1991 and was maintained at this level until May 2, 2000 when it was terminated and has never been implemented since.

4. There is simply no reason or need to turn Selective Availability back on and subsequent to this the next generation satellite design does not include an SA module. This is the US response to backing up thier claim that SA is not required as if it is not required then there is no need for the hardware and this is already a done deal.

5. There are several thousand continously monitoring ground stations around the world that record GPS 24/7 at 1 second (some even a 10Hz) intervals and there has never ever been a station record any Selective Availability spike since SA was terminated.

6. Comments such as yours is nothing more than peoples expectations based on incorrect information commonly spun by the press.

7. Your statement is totally and completely incorrect.

[Bonus]

SatNav, Thanks for your info and I will disable the Raymarine from SDGPS.

[marco]

1
11. New civil GPS accuracy specifications are being written as we speak and will be available around April 2008



would there then be gps updates needed for current gps receivers to handle any new specifications that you speak of ?

[SatNav]

1. No these new system specifications update specifications (such as accuracy) more in line with what the system actually provides as the current spec is getting outdated and now over 6 years old. A lot has changed in the past 6 years.

2. From about 2011 on (at this stage) will be a time when to look at GPS hardware updates to make proper use of additional signals.

[oldboot]

Ahh there's no substitute for quality information;D

thanks

cheers