iGage iG4, Руководство пользователя

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#11 Be Procedure Smart: avoid Blunders
Assuming that your receiver is in a location that is suitable for GPS observations, at a suitable time,
there are several procedural blunders that you can do to force a bad result:

Mounting system is not level and receiver is not centered over the ground mark.

Antenna height (HI) is wrong.

Antenna is mis-rotated, doubling antenna compensation errors.

Wrong antenna type is selected.

No battery in head with external power
Use a Fixed Height Tripod, Get the HI Correct!
The #1 OPUS procedure failure is a blundered instrument height. The ONLY HI that
OPUS will accept is the vertical height above ground to the ARP (Antenna Reference
Point) in meters.
If you use a tribrach, you are going to have to make a slant measurement and then
reduce the slant distance and SHMP (Slant Height Measurement Point) vertical
offset to a metric vertical height. The process is described on page 56 in the ‘Slant
Height’ to ‘Vertical Height’ section of this User Manual.
Slant reduction error is also very common source of blundered instrument height.
The iGx_Download tool makes this computation automatically for you, however you must keep track
of Slant vs. Vertical and Feet vs. Meters.
Transposition of digits in random heights that occur with tribrachs on tripods is a common source of
error. Measurement to the wrong place on the antenna is a common source of error. Mixing slant
measurements in feet with metric SHMT and radius constants is a common source of error.
Confusing slant heights between multiple occupations is a common source of errors. Using ‘inch’
tapes instead of ‘tenths’ tapes is a common source of errors.
All of these errors are eliminated if you use a fixed height 2.0 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 it 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
iG4 receiver: