MoTeC USA
GPS
3
Introduction
Thank you for purchasing a
MoTeC USA GPS
receiver. This user’s
guide was written to help you understand how the MoTeC USA GPS
(Global Positioning System) device works. Please read it thoroughly.
Installation is very important, and understanding how GPS works will
help you get the most from this sensor.
The GPS device uses an
antenna on top of the vehicle to
track satellites in orbit around
earth. It takes a minimum of
three satellites to identify your
position on earth, and a fourth to
calculate accurate timing.
Satellites are constantly moving, and a satellite which the antenna sees
at the start of the race might not be visible 60 minutes later. Satellites
used in the GPS solution are dynamically added or dropped based on
signal quality. Ideally you should have 8 or more satellites being
tracked in order to get good results. Anything under 6 satellites is poor.
With more satellites, there is more information to correctly identify your
position with less error. So it’s easy to see the importance of your
antenna having a clear line of sight to the satellites in the sky.
The system is a 12 channel receiver, but two of the tracked
satellites are special geostationary SBAS which provide DGPS
(differential GPS) via WAAS correction. Therefore the maximum
reported satellites in the data will be 10. Differential GPS uses those
additional satellites to more accurately calculate your position.
Positional accuracy goes from 3 meters to under 1 meter with
Differential GPS.
Warm Up Time
When the GPS receiver is first powered, it will start searching for
satellites to lock onto. This process takes time. It will take longer the
first time you power up at a new location from where you had previously
turned it off. Normal “cold” start up times, meaning being in a new area
from the previous location, can be anywhere from 2 to 10 minutes.
Subsequent “warm” start up times at the same location normally takes
30 seconds to 2 minutes. If you are outside of North American, expect
the very first time to take up to 30 minutes.
