Some of the documents on this webpage may be in PDF Format. Please download the Free PDF reader from Adobe to view these files.
|
Updated:
28 June 2005
AUSPOS FAQ-1. Introduction to AUSPOSOnline GPS Processing
Question 1.1 - What is the AUSPOS Online GPS Processing Service?The AUSPOS Online GPS Processing Service provides users with the facility to submit dual frequency, geodetic quality, GPS RINEX data to the AUSPOS GPS processing system and receive rapid turn-around ITRF coordinates and GDA for Australian users. This service works with data collected anywhere on Earth. It is a FREE service. This service is designed to process high quality GPS data that has been observed in long occupation sessions. A major aim of this service is to provide users with easy access to GDA94 (or ITRF for International users) using GPS 'base-station' type observation sessions. The service uses the latest available International GPS Service (IGS) products including precise orbits and Reference Frame. Question 1.2 - Where do I find it?The AUSPOS Online GPS Processing Service can be found at http://www.ga.gov.au and then follow "Geodesy & GPS" links. Alternatively you can go directly to http://www.ga.gov.au/geodesy/sgc/wwwgps/. Question 1.3 - Who can benefit from the service?The service targets users in a wide variety of application areas. Users include Differential GPS (DGPS) service providers, private GPS surveyors, government agencies, research and defence organisations. The service has clear benefits for remote regional users. Australia users benefit by improving access to the Geocentric Datum of Australia (GDA). Applications that are suited to this service include:
Question 1.4 - What do I need?Geodetic quality dual frequency GPS receiver data in RINEX format, web-browser, email address and an Internet connection. All the GPS processing occurs in the AUSPOS GPS processing server, so the type and capability of your computer is NOT important. Question 1.5 - What do I submit?
Question 1.6 - How do I get the results?The results are both emailed and a link is provided to our anonymous ftp server where the report is placed. If you receive no email message about your processing job it means that the email message has gone astray. However, if you take note of your processing Job Number and then visit our ftp site at ftp://ftp.ga.gov.au/sgac/wwwgps/ a file gps#####.pdf (where ##### = is your five digit Job Number) will contain your GPS processing report. Your GPS processing report is placed on our ftp server immediately after processing, but it may only reside on this ftp server for a short time. Question 1.7 - How accurate are the computed coordinates?The quality of the computed coordinates will depend upon:
Typically, a good quality geodetic receiver and antenna, with 24 hours of data using the IGS final orbit product, should give results to better than 10mm horizontally and 10-20mm in the vertical. However, 2 hours of data generally gives coordinates to better than 20mm horizontally and 50mm in the vertical. Remember the closest IGS station might be over 1000km away and the more data that is processed the more reliable the result. We recommend 6 hour observation sessions as a minimum. If your GPS station is greater than 100km from the nearest IGS station, then with good quality GPS data an indicative estimate of positional accuracy (3D) as a function of session length will be as follows: However, if you submit a network of stations that have observed simultaneously, then the relative accuracy between your GPS stations will be significantly better than those indicated above for short (<2 hours) observation sessions. Additionally, the absolute accuracy of your network, in ITRF and/or GDA, will become a function of your station with the longest observation session. The AUSPOS system will always use the latest available IGS products. The IGS final product is available ~2 weeks after observation, the IGS Rapid product is available ~2 days after observation and the IGS Ultra-rapid product is in part a predicted product available in real-time. The quality of these products and impact of the orbit error on a 1000km baseline can be summarised as follows (note the broadcast orbit is included for comparison only):
A poor coordinate solution might result if the submitted data:
The final coordinate will also be impacted if a user:
Question 1.8 - How fast is it?This depends on how much data you have submitted. A single site with 1 day of data should be completed within 15 minutes. A multiple site solution might take up to and over 1 hour. The processing times will also depend upon system load. Question 1.9 - How much does this service cost?It is FREE! Question 1.10 - What happens to my RINEX files?AUSPOS will NOT retain a copy of your data set. It will NOT, in any circumstances, release any submitted data sets to anyone. The only information of a processing job we will collect, is the user email, antenna type and height, and the final computed coordinates - just for our record keeping. Question 1.11 - What can't it do?The service does NOT process kinematic 'stop-and-go' or 'rapid-static' or 'single frequency' GPS observations. The service does NOT process 'GLONASS data', however if you submit GPS/GLONASS RINEX the GLONASS will just be ignored. Question 1.12 - Does any one else provide a similar service?The GPS processing service provided by AUSPOS is not offered by the Australian private sector. The service was designed as an additional free tool to be used by the Australian private sector GPS community. The AUSPOS service is an easily accessible Internet application that enables the Australian GPS community to obtain ultra-precise coordinates, to which they can value add. The AUSPOS service provides all processing results in both a nationally consistent Australian datum (GDA94) and an International Scientific Datum (ITRF). Processing services of this type have been traditionally fulfilled by the National Mapping Division. This service however, represents the first attempt by the National Mapping Division to provide access to a complex analysis system, via a simple to use WWW page, that is freely available 24 hours a day. Other International groups providing similar FREE services include: Other International groups providing similar COMMERCIAL services include: Please note that these services generally provide the processing results in "International Scientific Coordinate Datums" that are INCOMPATIBLE to the "Australian Geodetic Datum". Question 1.13 - Why do we make the service free?While no Australian private sector organisation provides similar services, AUSPOS provides the service freely to encourage consistency of all precise coordinates used by the public and private sector GPS community. By making the service free, the Australian Survey/GPS community can better compete for contracts throughout the world. Feedback from Australian private sector survey firms show positive support for the service. They are competing Internationally for contracts using the AUSPOS service as an important 'selling' point for own services. Effectively every small survey/GPS organisation in Australia now has access to a sophisticated GPS analysis system. For more information contact: geodesy@ga.gov.au
|
|||||||||||||||