AUSPOS - GPS Antennas
- Question 5.1 - Why do I have to specify the antenna used?
- Question 5.2 - What is the antenna height?
- Question 5.3 - What type of antenna do I have?
- Question 5.4 - What happens if I choose the DEFAULT(NONE) antenna?
To achieve the highest quality processing results, attention needs to be paid to the type of antenna used. Using the incorrect antenna type can introduce significant bias (more than 10 cm in the vertical component) and noise into the computed coordinates.
The actual observation point on a GPS antenna is called the electrical phase centre. The location of this phase centre is represented by a mean constant offset from the physical point on a GPS antenna, known as the Antenna Reference Point (ARP), and an additional variable offset that is dependant on the transmitting satellite's elevation.
The properties of the electrical phase centre are different for every type of antenna. Importantly, the electrical phase centre can be modelled provided you know the antenna type.
The antenna height is the vertical distance from the ground mark to the Antenna Reference Point (ARP). The ARP is the physical point on a GPS antenna that measurements are typically reduced to. The ARP varies between antenna types. As a WARNING, the ARP is rarely the top of the Antenna Ground Plane. The ARP height should NOT be confused with slant and other instrument height measurements commonly used in GPS processing.
AUSPOS uses the IGS antenna naming convention. The IGS - Naming Convention Document provides more information.
Further information regarding the specifications of antennas can be found on the National Geodetic Survey (NGS) antenna calibration web site.
If you choose the DEFAULT(NONE) antenna type; no antenna phase centre model or offset is applied.
If you set the antenna height to 0.0000 m and choose an antenna type, then the position of the ARP is computed.
Topic contact: firstname.lastname@example.org Last updated: February 10, 2012