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Trying to Understand GPS Antenna Offests  

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The Pseudo Ranger
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Solutions Locus Antenna Offsets

If I go to the GNSS Solution: Tool/GNSS Antennas/Double Click Ash_Locus

I get this:

Am I misreading that? Why a difference between the antenna.inf and what it shows internally?

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The Pseudo Ranger
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Solutions Locus Antenna Offsets

There are actually two entries in the .inf file for the Locus:

[ASH_LOCUS NONE]
Description=Integrated L1 only Display to South
Radius=0.0
SHMPOffset=0.0
L1Offset=1.9 1.3 158.0
L1Phase=0.0 0.0 -8.2 -3.9 -0.7 1.6 3.1 4.1 4.5 4.5 4.1 3.6 3.0 2.2 1.5 0.9 0.4 0.1 0.0
L2Offset=0.0 0.0 0.0
L2Phase=0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

[800372]
Description=Locus
Radius=100.0
SHMPOffset=125.0
L1Offset=0.0 0.0 125.0
L1Phase=0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
L2Offset=0.0 0.0 0.0
L2Phase=0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

I beleive the [800372] is the left over one from Ashtech Solutions.

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Paul in PA
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GNSS Solutions Locus Absolute Antenna Offsets

[ASH_LOCUS]
Description=Integrated L1 only Display to South
Radius=0.0
SHMPOffset=0.0
L1Offset=2.5 0.9 139.9
L1Phase=0.0 0.0 -3.7 -3.2 -3.0 -3.0 -3.1 -3.3 -3.6 -3.7 -3.8 -3.5 -3.0 -2.4 -1.7 -1.0 -0.5 -0.1 0.0
L2Offset=0.0 0.0 0.0
L2Phase=0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

The absolute antenna offsets differ from the older relative offsets. You can use either but you must not mix and match. International antennas probably will not get an old style NGS relative test, so if you use any of those antennas then you have to use the absolute for all your future work.

Notice radius is zero, so if you use slant height measurements in the field you may have to do the math yourself. When I query the antenna in GNSS Solutions I get an h value which is needed because the slant height is to a point on the measurement hat which needs to be accounted for.

Paul in PA

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X-PAD Ultimate from iGage

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