Optimal pole height for GNSS

Taller is better for sky visibility and usually multipath reasons. However with taller pole easier to be out of plumb assuming your looking at a bubble half way or less up the pole and you get more run out (i.e. banana shaping in pole) in a longer pole typically. Also longer pole feel less balanced to carry if that matters to you.

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1.8-2m hopefully has been arrived at for a reason.

It depends.?ÿ As long as the antenna has a clear sky view down to 10?ø or so above the horizon, any height above about 5 feet is fine for modern antenna designs.?ÿ I still use 2m fixed-height tripods for static work, but for RTK I mostly run a 5.05 pole (5.00 feet on the pole graduations) with no problems.

@jim-frame?ÿ

Doesn't your head/shoulders start obscuring the horizon with a pole that short?

That's what I thought would happen, but after experimenting I found that in wide-open areas raising the pole above my head made no discernable difference.?ÿ In compromised sky view situations all bets are off, sometimes you need all the help you can get.

I've been using a 2-meter rod since forever and it seems to work out alright.?ÿ Now a days I'm far more nitpicky about the weight.?ÿ The TSC7s permanently rubbed me the wrong way I think. ???? My GPS setup right now is the best one I've ever worked with-- 2-piece carbon rod with a TD600 collector and a 12i receiver, R8s base with a cowbell so I don't have to screw with batteries.?ÿ The rod is so light it's like surveying with a pencil.

I frequently use a 10-25 foot pole for my base in order to lower the horizon line in these NH and Maine woods. When the base is up that high, I donƒ??t set it on a known point, but I set it within a few feet of the known point, then localize in with the two-meter rover. As long as the base is stable, Iƒ??m OK with it.

I have always used an extendable pole with graduations. One that works well is a graduated pole with insert stops along the length. That helps when it's extended to not get the incorrect pole height. The 2 meter fixed poles just didn't work well with 4-wheelers, trucks and the type of work I do.?ÿ

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The first GDM4400 had poles with pin stops - due to the weight of the first RPU heads you couldn't rely on the usual twist lock to hold solid.

The same reasoning will apply to a GPS on a pole - you don't meed to change the height very often and changing the pin position "SHOULD" remind you to change the rod height in the controller.

I've seen in the past where some field crews would use something extendable like a grade rod with threaded rod or double ended 5/8-11 adapter to elevate older receivers when in deeper woods. Usually this helps and worked well for things like wetlands boundaries needed to be located but the horizontal & vertical locations might not have needed to be super tight (~1' as these areas were well enough away from the limits of disturbance). But I would hate to drop the receiver attached at the end of a pole from say 20-25' up

Those really high-rod setups won't be good for much better than a couple tenths unless they're braced extremely well, which rules out your average setup kicking around in the back of your average survey chariot. There's a point of diminishing returns where your centering errors overcome any benefit that increased sky gets you.

That happens pretty quick unless you have a super-solid setup and a super-sensitive rod bubble.

Sometimes all you need is a couple tenths, though.

Thanks for the info

I will play the other side of the coin just to get the brain waves thinking. If you use no rod and allow the earths surface to become your ground plane you just might be surprised. Now that is not practical for everyday survey work nor for rtk really. ?ÿBut a little test you can do is get a small rod on a nice clear sky to a very good known point about 3 ft high roughly. Keep your body away and observe for say 4 hours at say 15 minutes intervals. Then do the same with the 2m rod most use the next day same time. See which you think comes closer to truth. But even this little test is not practical either. But when studying for days and many hours worth of data some things will really surprise you. Especially the earth as a ground plane. You can play that test fairly easy by burring an old zepher type antenna where the top is above the surface or equal to it and just let it burn logging data.?ÿ

I like the adjustable rods idea. Because in a sticky situation you can observe and change the environment a little by changing the height of antenna. ?ÿ

yƒ??all donƒ??t beat me up to bad just wanted to chime in. All had great ideas. Just a little testing I have been around that as a surveyor we donƒ??t ever get to do. Manufacturers and geodetic and orbital scientist types do these crazy things.?ÿ

Like Jim Frame, I use a Triumph-LS with a short (~5 foot) rover pole. It's better balanced and has less runout and less centering error than a longer pole. Most of my shots are out in the open and I keep my body away from or below the antenna to avoid blocking its view of the sky. The Triumph-LS shows a scatter plot of the epochs as they are being collected, so you can see in real time how much blocking part of the sky has on the computed position in all 3 dimensions. It's generally less of a problem than you might think. If the sky gets blocked for a few seconds, I either reject the shot and start over or let it collect long enough that the problem epochs don't significantly affect the average.

I'll use the 4.40' height sometimes when working in woods.?ÿ Extending the rover pole up to 6.562' into a mess of Elm or Juniper branches and wondering why you can't get a solution never made sense.

Posted by: @olemanriver

use no rod and allow the earths surface to become your ground plane you just might be surprised. Now that is not practical for everyday survey work nor for rtk really. ?ÿBut a little test you can do is get a small rod on a nice clear sky to a very good known point about 3 ft high roughly.

Laying the antenna on the ground point makes some sense if that leaves a good sky view, which would not happen often for most people.

At 3 ft, the antenna is multiple wavelengths above the reflective ground, so if multipath off the ground is an issue at 2 meters, it still is here.

If I remember right, I was told at a seminar recently that being too high can cause multipath problems from below because the software isn't programmed for something like that and possibly wavelength issues.?ÿ?ÿ

I absolutely despise a fixed 2 meter rod with a bulky data collector stuck on the side.?ÿ Going through the brush with that is impossible to not get perpetually hung up on sawbriars and wild grapevines.?ÿ My favorite setup is with the Javad where the data collector is integrated into the head instead of a separate unit and a collapsible rod that allows the whole thing to literally tuck under my arm.?ÿ At first, I was wary of my body being in the way at a 5' or less HR but my head seems not to matter.?ÿ It may be empty and not block the satellites.

Not recommended. Taken from: https://www.photolib.noaa.gov/Collections/Geodesy/emodule/519/eitem/7001

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@bill93 well the earth actually is the best rf filter not water or shiny grass but bare earth. This is simulated through materials that are tested when placing antennas on roofs etc with different materials to help reduce multipath or noisy data. Les of a chance in open sky of multipath at 3ft vs 6ft to be honest. But yes at 3 ft you can still get multi path. Remember also at whatever your elevation mask is itƒ??s supposed to reject those signals. But hey we have folks thinking lol. 3 ft is tough to do as my big head and body gets in the way. Lol.

Back in the early 90's we were doing a USGS project in northern California. This was in the days before RTN and there were very few CORS around, so we ran static and tied in existing passive marks. I sent one of the observers to occupy an existing NSRS station at a USFS helipad. He got there, and there was a choke ring antenna sitting right on top of the disk. So he proceeded to try and setup over the crossed dipole, thinking that was the station. Someone came running out of the building in a panic yelling at him. At the time I thought it was pretty strange that they placed the antenna directly on the mark, at basically ground level. There is now a CORS at the site. It is still on the ground, here is a photo from the NGS web site...someone set a target on it also.?ÿ

In the same job I went to occupy a "HARN" station, which was shown on the data sheet as order B and occupiable with GPS. It was under/between two very large pines. So I wondered how it could be order B and a HARN. I found out that someone in NGS had tried to classify all Trans Continental Traverse (TCT) stations (the survey was nominally 1:1,000,000) as order B, and in the process they got classified as GPS occupiable.?ÿ