Q & A Information Sheet
What is TrigNet?
TrigNet is a network of continuously operating GNSS base stations covering South Africa all managed and controlled by a single control centre situated in the offices of National Geospatial Information (NGI). The first stations in the network were installed in 1999 and by September 2010 consisted of more than 55 operational stations, further stations are planned to expand the network.
What is GNSS?
GNSS is the generic term used for Global Navigation Satellite Systems and includes the United States of America Global Positioning System (GPS), the Russian Global'naya Navigatsionnaya Sputnikovaya Sistema (GLONASS), the Chinese Beidou or Compass system, the European Union Galileo system and other similar systems.
What is the purpose of TrigNet?
In order to achieve sub-metre positioning accuracy using GNSS, users must operate at least two receivers one of which must be placed on a point of known position which implies that users must purchase two or more GNSS receivers. TrigNet effectively provides the second receiver thus eliminating the need for the user to purchase more than one receiver which reduces the capital outlay to get started in high accuracy GNSS positioning.
How does TrigNet work?
Each of the TrigNet remote stations records GNSS data on the two frequencies of GPS at all stations and GPS and GLONASS (for 12 stations only), at a rate of one observation per second commonly known as a 1 sec epoch rate. The data is streamed to the control centre at NGI using dedicated land line connections. The data is processed at NGI and made available to users for either post processing or real time applications. Post processing data is made available in the Receiver Independent Exchange (RINEX) format and real time data is made available in the Radio Technical Commission for Maritime Services (RTCM) format and as the names imply, both formats are independent of any specific receiver manufacturer. Real time data is made available to users via the cell phone connections to the internet while in the field.
What products are available?
Post processing data provided in RINEX format:
- 1 sec L1, L2 1 hourly data available within 30 minutes after the hour;
- 1 sec L1, L2 24 hourly data;
- 5 sec L1 24 hourly data; and
- 30 sec L1, L2 24 hourly data.
Real Time data is provided using the Networked Transport of RTCM via Internet Protocols (NTRIP):
- DGPS (~0.35m accuracy) countrywide;
- RTK (~0.05m accuracy) within 30 – 40 kms of each station using a single base technology; and
- Network RTK (~0.03m accuracy) within the Gauteng, Western Cape and KwaZulu Natal clusters.
All products and services from NGI are free of charge.
Where can I get further information on TrigNet?
Tel: 021 658 4362 or 4363 or 4304
Fax: 021 658 4357