Gps pole height

I think that would depend on how dense he is.

What's his cross-sectional area?

The higher the better to clear obstructions and better sky visibility would be the general rule.

However the longer the pole the more run-out/banana it's likely to have (no pole I've ever used is perfectly straight at 1.8m+, may only be a mm or two but always something.  Plus with the longer pole any maladjusted bubble makes a bigger difference (one bump in field can knockit out sometimes, need to baby that pole).  You can cancel these out by taking a shot, rotating the pole 180°, taking a second shot and averaging.

Or if you are just setting up an RTK base not over a mark and observing all points with rover facing exactly same direction (i.e every shot facing north) the bias are all consistent and relative precision is maintained but that takes a lot of discipline!

Lazy pole plumbing also makes more difference the longer the pole but that can only be fixed one way...

If he is blocking satellites with his head or body that could cause issues. If he has reflective materials clothes etc multi-path could come into play. However on the scientific side the earth makes the best ground plane. So if you placed the antenna where the APC was only visible thats the best solution.  I often change the height between observations enough to get a different part of the wavelength of the signals.  As far as rotating pole for plumbless. A practice i which has been done before gps with prism poles and such it works. But with gps every antenna has a north reference position. The antenna calibration files not only correct for the APC to ARP for the height offset but also horizontal. So it is a North East and Up.  Every model every manufacturer has different values. Even the same exact models can differ by mm between the known.  Now some antennas if you rotated say 180 you could introduce errors in the cm range from not having it oriented correctly.  I never worry about this doing topo or mapping. I do pay attention for my control and any property corners i am setting or locating. Understanding errors is something we all have to deal with and we all deal with error sources sometimes differently. Lets say my pole is out of adjustment not plumb.  Well if I rotate the pole i can mean this out. If i don’t then I create a systematic error.  This is just in the pole not the measurement itself. My systematic error keeps me relative to each of the other control points and and property corners in this scenery but causes a systematic error to the datum or coordinate system i am on at the time. It takes 5 minutes or less to set up pole and bi pod and slightly loosen and rotate and check bubble. Now to look for the banana effect its not done daily because that takes setting up instrument and sighting and such.  

It depends on what I'm doing.  I'll run it at 4.5ft if I'm doing an as-built of a landfill gas system where I'm generally getting 20-29 satellites.  If it's windy and I'm hitting a control point, I'll set it low and just grab the DC and move away before I start observing.

I see no reason to set it any higher than just above your head.  Whatever gain there is in running a 2m pole is quickly cancelled by the fatigue to joints, the increased chance of bashing the receiver when navigating through the woods or in and out of vehicles etc..

A human body will block signals, no question. Nevertheless, I've run RTK with rods lower than 2m plenty of times and it doesn't cause any real problems.

Now some antennas if you rotated say 180 you could introduce errors in the cm range from not having it oriented correctly

Which receivers are this bad off centre?? Looking at antcal for anything I've used lucky if it's a couple of mm.

@lukenz 

I agree. In the earliest days of GPS maybe. The documentation for my Leica GS18 makes no mention of antenna orientation. I’m confident that if Leica thought there was a fraction of a millimeter to be gained they would. 

I was skeptical about claims that orientation of my Javad Triumph-LS mattered, but then a few years ago I did some calcs using the antcal file.  As I recall, it was particularly important for vertical results, on the order of 0.1' in a worst-case scenario.  Ever since then I've paid attention to the orientation.

@lukenz I would just go to the NGS site and look at the file for your antenna and do the math. Remember no matter what it is you double that at 180 degrees.  I hqd never tho and it much since the old days until someone who actually performs these calibrations on all antennas said to me you might want to consider that. Some in rtk would be in the noise. But some he said could be a few centimeters so i figured if doing static most definitely if doing rtk for control or position property corners i better just be safe.  We only use the r10 and r12 here so i have not cked personallyall brands.

@olemanriver 

Yes that's the antcal file I was referring to and like @mark-mayer the Leica GS18's I mostly use (and everyone other one I looked back that I've used last decade) are mm differences only.

@mark-mayer 15 years ago about. A manufacturer sent in the 3 antennas to be calibrated all the same model. Those 3 antennas all agreed to a few mm of each other.  At that time that antenna group had the lowest numbers of any manufacturer. Of agreement between the 3.  Thats in the build quality. Relative antenna calibration.  So the antex file is derived from 3 of same model at minimum. 3 mm is not a lot but that’s only in the 3 that were tested of who knows how many to derive the antex file. So i tend to lean in the direction that its not only the antex file not just the bubble but try and eliminate or control what i can within reason. If 3 mm was low between exact same models of a geodetic antenna what are our chances we have more error in an all in one. To me i can only look at the facts and try and mitigate or accept and control those error sources and weigh them against time (money). To me it takes no longer to orient to north on a control point than to not do it. One of the first things i ask of a new hire when i get on site is tell me which way north is. One it helps me t teach them to orient the plat and site right from the beginning. 2nd as they learn to set up a base or rover over a point i am also re emphasizing that and I am also being consistent around the site with my equipment. I will not argue that in most cases its in the noise of rtk. But when its not i have covered that hopefully in the muscle memory as a new piece of equipment lands in my hands.  Yes the old days we had a big arrow engraved or marked on the antennas ground plane which was removable for rtk use and or marked on the antenna itself. Now we have something the size of my starter coffee mug in the morning lol. We also today vs then have more than a L1 and L2 band and none of the signals come in at the same exact location. So if i am wrong and I always face orient in the same cardinal direction both antenna and bubble at-least i am consistent and relative .  But i don’t think its as tight as we assume and I assumed it didnt matter either. But after processing several jobs least squares and applying the same centering and height error and looking at the same rms raw i can see where it gets me over the hump in short baselines or points between corners for ALTA specs. And such. I could be over kill for sure.

@lukenz how many mm on your system now add atleast 3 mm to that plus or minus because no one antenna exact same model would be much closer the. Double it at 180.

https://geodesy.noaa.gov/ANTCAL/docs/NGSantcalprocedures.pdf .  One of the things is in all of this that the whole file antex etc is based off facing the antenna north. Its a map of signals that dynamic not stationary. North east and up are relative to ARP. All based off the antenna facing north. True North. But i eyeball that or know roughly compass mag declination. Or convergence in my job site. I am not perfect just try to eliminate all. Now ngs calibrations are different than manufacturers as well. 

the Leica GS18's I mostly use (and everyone other one I looked back that I've used last decade) are mm differences only.

It depends on the azimuth and your mask angle.  With a 10° mask the GS18 maxes out at about 4mm at certain azimuths.  With a 0° mask that runs up to almost a centimeter.

And I misremembered about the Javad, it maxes out at about 14mm, not a tenth of a foot.

@jim-frame 

Are you looking at antex or antinfo? Assume you are looking at L1 differences? I really need to look on PC with a proper screen much harder to make sense of on phone!

Also I would make the assumption that for base/rover RTK which I thinking here using less than a 10° is borderline negligent and I'm often using 15° (at least at the rover) which is the 2mm level in the antex file for GS18 as best I could see.

@olemanriver 

I can accept that if you are doing static GNSS using well adjusted high quality tribrachs then pointing all the receivers in the campaign to north is important.

But for RTK GNSS on a 2m pole (no matter how much you baby it) the run out/bubble going off adjustment (a minor bump during the day your assistant forgot to tell you about) is a bigger source of error to me; one the 180° observation 'pairs' solve.  One is a cm issue and the other is mm issue.  However if your pole is well adjusted (both bubble for plumb and run out accounted for) along with well adjusted tribrach under the base then having base and rover facing north will yield the most precise results.

As an aside run-out of the pole is not so much of a problem if you adjust your bubble so the tip and top are plumb at a fixed height and only take observations using that height, perhaps a good argument for fixed height poles? However this kind of like adjustment requires a total station to sight up and down pole plus lots of iteration compared to those pole jigs on the office wall so less likely to be done as often as you really need to.

@lukenz Also this will probably throw you for a loop. static. if you process with an absolute antenna cal file and do not orient the antenna correctly it can throw off the vertical. test show up to a cm in that as well. I agree that in rtk mode DEPENDING on receiver especially newer ones it is possible to be in the mm range. and lets say rtk is 8 mm accuracy + 1PPM just pulling a spec.  thats in a perfect world and say the offset is 3mm its in the weeds. BUT it is something I can control and that 3 mm turns into 6 mm that's .02 ft plus the random error of the 8mm. Now let's say that we have only a few mm in the specs built  between the same model base and rover. If no attention to detail is paid we have more random error and if we pay attention to details we control some of that error to me it's just makes for sound field procedures and takes no more time and allows me to control and be a bit better when things get close. if it were only .01 ft I am gaining then so be it. Yes pole run out 40 min buble. we deal with all sorts of errors we have as surveyors for years. Direct and reverse readings on total stations and transits multiple readings methods were designed to reduce those. I dont topo orienting it but when I am now establishing RTK control and a 1 mm + 1 ppm edm is shooting distances from that control and I am getting .025 at most 95% of the time on ground verifications at distances between 300 to 1000 ft on my job sites with good tribrachs and traverse kits I can trust that my procedures are doing what I want and I am happy. Yes we get the tenth or so sometimes we get .05 ft sometimes. Vertical is coming in very tight as well. I only do it for control and property corners and in the east we do more RTK for control why MONEY TIME but I dont buy it I did static fast static a lot when I was out west and wish we did more of that here but its just get rtk control and move on. Many of our projects here in my opinion should be static for primary control but its not in the budget they say.