Specifications

269
Assessing MobileMapper Beacon
Reception Quality
As long as the green lock indicator light on MobileMapper
Beacon stays on, you can be certain that ProMark3 can readily
deliver a DGPS solution using the incoming correction data
packets from MobileMapper Beacon.
But if you notice that the green indicator light on MobileMap-
per Beacon sometimes temporarily turns off, this means the
signal received is not as strong as it should be. The reasons
for this are the following:
- Too many obstructions between you and the station. See
how you can limit these obstructions.
- Or you are nearly out of range of the station. Consider
working with a closer station, if possible.
- Or atmospheric noise has significantly increased thus
reducing the SNR. Consider working with a station that
would give a better SNR.
ProMark3 gives you the ability to analyze the key reception pa-
rameters of the MobileMapper Beacon. You can do this any-
time, when setting the DGPS beacon mode, or later while
using the beacon provided you first ask ProMark3 to stop pro
-
cessing the incoming correction data packets. This is done by
tapping the Disconnect button in the DGPS Configuration win-
dow. You can then tap on the Settings button and then on the
Details button to view the Beacon Details screen. (See also
page 213.)
Among all the parameters displayed on this screen is the Sig-
nal to Noise Ratio (SNR). This is the most important parameter
to look at.
The table below gives indications on how safe DGPS operation
with MobileMapper Beacon will be, depending on the value of
the SNR.
SNR DGPS Data Reception Quality
SNR<10 dB Very Critical; DGPS mode steadiness is very unlikely.
10 <SNR<20 dB
Good but critical; if signal deteriorates, even slightly,
ProMark3 won’t be able to maintain DGPS mode.
SNR>20 dB
Excellent; there is signal level “in reserve”, which means even
if the signal slightly deteriorates, DGPS mode will be main-
tained.