Has anyone tried a Choke ring antenna as apposed to a ground plane and is there any advantage ?
A choke ring is better at rejecting multipath and may have a slightly better S/N ratio, but unless you're doing very long sessions (i.e. an infrastructure installation) and processing against other fixed sites, I don't think you're going to see any advantage over a modern ground-plane antenna used in a decent location.
Choke rings are way too heavy and bulky to be suitable for rover use, and because all the ones I've seen are milled from a solid block of aluminum, they're very expensive.
I have a couple (just the rings, no antenna elements) that I picked up years ago just for fun (and for very little money). They're pretty cool as machined devices go.
This depends. Multipath signal to noise many things come into play and technically the statement one is better than the other depends on many factors. Near far ranging what the specific area is like what is causing the signal interference etc. if you are on the ground doing surveys and not setting up a semi or permanent station then depending on what type of work you are wanting to do a regular ground plane is sufficient in most circumstances. Having repeated measurements at different heights would be better than worrying about the extra cost and hassle of lugging a choke ring antenna around. Having a good all the same set model of antennas is better in most situations. GPS in general is a unique beast. So many different ways to accomplish canceling or mitigating errors. We all discuss multipath often. However there are clock bias in each receiver, absolute vs relative antenna calibrations how different manufacturers account for radio bias and handle that. These are just a few things and we have not even touched on the centering over a point like we do on this side of the house and height measurements etc. If I were setting up a permanent station I would possible lean towards a choke ring and depending on geographic area how much snow or pigeons were in the area maybe add a radome which comes with it’s own pros n cons.
For what’s it worth a zepher geodetic can achieve the same accuracy of a choke ring when fabric is used in certain situations. If you want the best then lay your antenna within the earth and let the ground become your ground plane. Topcon also has some very good geodetic antennas at least they use to highly repeatable in there builds. I forget which particular model it is was but relative it was the tightest in that precision realm.
what are you trying to achieve and requirements you are looking at acquiring.
For what’s it worth a zepher geodetic can achieve the same accuracy of a choke ring when fabric is used in certain situations.
Fabric? Can you clarify?
I used to use Microcentered and Compact L1/L2 antennas with the big ground planes for GPS (only) static work, but about 10 years ago I picked up 5 each Zephyr Geodetic units for $35 apiece. They're smaller, lighter, and perform at least as well.
https://geospatial.trimble.com/en/products/hardware/trimble-zephyr-3-geodetic
https://geospatial.trimble.com/en/products/hardware/trimble-choke-ring
fabric was a spelling mistake.
I want to establish a highly geodetic network.
Which of the above are better?
@jim-frame different types of fabric have been tested and utilized in scenarios to lay down on building roofs etc. beneath the mounted antenna which has aided in reducing noise multipath etc. nothing we would use on a daily basis etc.
We had one site that was on a bldg next to ocean. That antenna was mounted above the wall at top of flat roof. No other objects surrounding it. We tried chokerings zepher geodetic and other antennas. For giggles we took it out of the network solution and simply raised it a couple feet with an extension pole temporarily. That alone was enough to make the noise go away from near multipath which I believe was from the water. Ocean bay. Now for fabrics and meshes those have been tested and do quite well in certain environments. I will see if I can find any online studies on the subject. I think geo++ did some. I will look around at other universities etc as well when I get some free time.
@johnymal The NGS uses the regular ground plane antennas when on marks. So zepher. On a station that will be staying put I would go with choke ring as the heat cold weather it would last longer. I have seen zepher’s on a station aka CORS stationary year around separate before . If you are in some areas that you need and must have observations to and bad multipath such as tin meta shiny roofs big signs etc I might would use a choke ring. But if you are on the ground doing this and setting marks in the ground don’t waste the money on choke ring. The zepher is going to give you great results if you are following the minimum double occupy and setting these marks in good areas. Get a klinometer and do obstruction diagrams on all proposed new and any control that exist. Plan the survey well. Give your self a 3 hr gap in time between. Nice long observation times for longer baselines etc.
@olemanriver I have a thought to establish control network in each floor of a 15 story building as I can not transfer it after 3rd floor. Due to fact that we have narrow spaces and there are not availiable holes or a shafts.
The building will have a kind of net like the foto in all floors.
Well you are not planning on using gps inside a building I hope. Thats not a good use for gps and even if you could get signal that’s some very short baselines . You probably need a total station or robot for that work.
@olemanriver I am a surveyor.
Ι was thinking if was easy to establish local network with zephyr antenna as Trimble advertise that is accurate. Just asking for an easiest solution.
Gotcha. I see no difference in either as they both have an antenna cable and both fit 5/8 thread. So using is no different. If hauling them around I would choose zepher. If setting up and leaving for infinity the choke ring.