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iGage iG9 User Manual
All these errors are eliminated if you use a fixed height 2-meter tripod or a 2-meter pole with a
Hold-a-
Pole for every static occupation. The answer is always just “2.0” meters. Which is very easy
to remember.
Rotate your Receiver Correctly
Every antenna has a ‘correct’ rotation. It is VERY important to spin the antenna so that i
t faces the
correct direction.
You can determine the correct rotation for any modeled antenna by looking up the antenna
definition on the NGS Antenna Calibration website. Here is the information from the NGS site for the
iG9 receiver:
The iG9 should have the MMI (the button/LED panel) turned to face the North.
What happens if you don’t rotate the antenna correctly?
OPUS has a calibration file for every
antenna that relates a change in L1 height offset by the position of the satellite in the sky and the XY
offset of the center of the antenna from the center of the mounting nut.
OPUS compensates for the northing, easting offset assuming the antenna is facing North. If you
rotate the antenna 180
°
so that the MMI is pointing to the South, then the offset error is doubled,
and your final solution will be in error by double the centering offset!
Bad rotation alignment can also be responsible for making an occupation appear noisy. OPUS
compensates for the antenna vertical offset changes depending where satellites are in the sky. If
you mis-rotate the antenna then the compensation will be applied incorrectly, perhaps doubling the
receiver’s centering error
.
Use the Correct Antenna Model
Make sure that you have the correct antenna model selected. Some antenna have multiple radomes
and revisions listed.
For example: the Ashtech version of the Dorne Margolin chokering (which is a replacement of
ASH700936 which has even more models and revisions) has 10 revision and dome combinations:
