iGage iG9 User Manual
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ASH701945B_M NONE
ASH701945B_M
SCIT
ASH701945B_M SCIS
ASH701945B_M
SNOW
ASH701945C_M OLGA
ASH701945C_M
SCIS
ASH701945C_M SNOW
ASH701945C_M
SCIT
ASH701945C_M PFAN
ASH701945C_M
NONE
Each revision has a different calibration, you must select the correct model, or you will introduce
substantial height uncertainty to your solution.
Batteries In or Batteries Out?
Everything
inside an integrated receiver’s body changes the effective antenna calibration.
Everything.
Slight changes in the PCB’s, UHF radios being installed / omitted
, the cellular modem model: they all
result in a change in antenna calibration. Sometimes the change is very small and other times a
seemingly innocuous change will result in a substantial phase center change.
iG9 receivers are calibrated with two batteries inserted into the battery compartment. If you power
an iG9 with external power, you should still include batteries in the head to match the original
antenna calibration conditions
#12 Why does Modern RTK work where OPUS fails?
Yes, OPUS is substantially more finicky than modern GNSS RTK. OPUS jobs routinely fail in places and
at times that iG9 RTK works flawlessly.
There are two primary reasons: number of satellites and baseline length.
Number of Satellites and Signals
OPUS is GPS only. Modern GNSS RTK uses additional satellites (GLONASS, Galileo, BeiDou) and
additional signals like GPS L2C, GPS L5 and GLONASS L3.
Compare these two sky plots (same time, same location):
GPS Only
GPS + G G BeiDou
More satellites are better. More signals are better. Even though the iG9 tracks GPS, GLONASS,
Galileo and BeiDou satellites, OPUS currently only uses the GPS observations. So, a great
constellation like the one on the right is reduced to the minimal constellation on the left.
A modern GNSS RTK receiver has and uses more signals at all times than the OPUS processing tools.
Baseline Distance
OPUS processes GPS baselines from your receiver all the way back to each individual CORS station.
Typically, these will be 45 KM (28 miles) to 150 KM (93 miles) baselines. In some areas the nearest
CORS station might be 250 KM distant!
RTK processes the baseline from your RTK Base to your RTK Rover which typically will be less than 10
KM (6 miles.)
