I know I am late to the party. I picked up this thread in a search and there are some questions which occur to me.
The pictures I posted above are of an aluminium 100mm extension and a carbon fibre 100mm extension. There is a different consideration due to effect on the internal antenna of the metal pole extension.
For a static survey and post processing I always use the 100 extension with a tribrach and adapter.
I can use the appropriate designation.
My GPS pole is carbon fibre.
Most of the Trimble poles I have seen have an aluminium inner pole within the carbon fibre outer and I am sure there are others.
Surely the extended inner pole has an effect on the antenna height ?
In my opinion there is no way nearfield multipath with a 10 cm piece of metal under the unit can cause 5 cm of difference.?ÿ Maybe a millimeter or three, but not 50 mm.?ÿ
I??m planning an experiment to see if things under my GPS antenna affect the measurement of height. I??ll use an antenna mounted 1) close to a metal tripod, 2) with 20 cm of wood added, or 3) with 20 cm of metal tube added. It won??t be exactly on the tripod because I need a layer of masonite and a nut to hold a fixed position for the tube and wood.
Although 10 cm is of more interest on the particular antenna discussed in this thread, the additional height is a little more relevant to me because I often use either on the tripod directly or on a 2-meter metal pole. I figure 20 cm will be enough to see if there is an effect and easier than rigging 2 meters of wood.
I plan to set up two receivers (4000sse) a few feet apart, with one using a TRM14532-00 ground plane antenna as the reference and a TRM33429-00 ??microcentered? as the one in each of the three positions. The choice is because I would expect more effect, if any, without the ground plane. I??ll take maybe 5 minutes in each position at 10-second rate, and process together in Topcon Tools to get vectors between them to compare the relative heights values.
If I get a significant difference then I??ll probably repeat using the 33429 as the fixed reference and moving the 14532-00 ground plane antenna, since that is the one I??ve always used for GPS on Benchmarks.
I??d rather have you throw rocks at the plan now, rather than tell me afterward that I did it wrong. How long for sessions and at what rate would you use??ÿ?ÿ Other comments?
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My conclusion is that I found no significant difference with various things under the Trimble 33429.00 "microcentered" antenna.
Measured height of the nut above an arbitrary reference:
?ÿ 3 mm with 20 cm metal tube
?ÿ 7 mm with 20 cm wood
20 mm antenna on nut
?ÿ 8 mm antenna on nut, repeat
It turns out I set the sample rate in the wrong place in the menus and they were at 10 seconds.?ÿ I ran each session 20+ minutes, at least 120 epochs.?ÿ I barely had enough common satellites for the earlier sessions, and more toward the end.
I know this is an old topic. But thought this might help some of you and seems to make this topic more cloudy
, and I would like feedback if any of you are still watching this forum because I'm not confident in this...
According to this NGS/OPUS response I got, the resulted orthometric height difference is actually .037 meters in the other direction (compared to ARP measured on receiver and NOT selecting +10 option).?ÿNot .052 meters?ÿas stated earlier in the forum See reply below and my?ÿ my results from the same log file. This considering the guy from NGS is actually right. Also note you have to measure from the bottom of the the 10cm topcon part. NOT the ARP on the antenna itself if that makes sense, according to NGS.
NOTE: These scenarios were OPUS'd two months ago and I resubmitted them today and are they Precise Ephemeris, not Rapid.
- ?ÿ?ÿ Scenario 1.
- Antenna selected on OPUS page: TPSHIPER_V NONE
- Measuring point-ARP on the bottom of receiver
- ARP height entered in OPUS: 1.698 meters
- Ortho Height: 427.636 meters
- ?ÿ Scenario 2.
- Antenna selected on OPUS page: TPSHIPER_V+10 NONE
- Measuring point-ARP on the bottom of receiver
- ARP height entered in OPUS: 1.698 meters
- Ortho Height: 427.573 meters
- Scenario 3.
- Antenna selected on OPUS page: TPSHIPER_V+10 NONE
- Measuring point-BOTTOM of 10cm/100mm piece. 1.598 meters
- ARP height entered in OPUS: 1.598 meters
- Ortho Height: 427.673 meters
All scenarios were from one project where we had no recently verified NGS marks and the one we had was in thick vegetation, and we had no cell service to access the network here in Nebraska, so we differential leveled out to open area on a control point, closed, and I OPUS'ed this point 6+/- hours. Scenario 3 was actually the farthest elevation of the three Scenarios I put into OPUS. The mark's elevation was 427.488 meters from leveling off the NGS benchmark, a difference of .185 meters from Scenario 3, which doesn't give me a lick of confidence. I need to keep testing this, though.
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Hello Quinton,
For the Topcon Hiper_V+None?ÿ that does not use the factory spacer, the ARP is measured to the bottom center of the antenna (
).
For the Topcon Hyper_V+10+None that uses the factory spacer (part # 51949), the ARP is measured to the bottom center of the spacer as is shown in the drawing that you provided (
).
As you can see, the ARP location that you measure to is determined by whether or not you are using the factory spacer.?ÿ ?ÿIf you would like further assistance, please reply to this email.
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Regards,
Dave
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