From Leica's website (straight copy and paste, no 1st hand user experience here, but am a long time Leica user so follow their stuff closely):
What makes the GS18 T different? How does it work?
The?ÿLeica GS18 T?ÿis different from any other product in the market because it does not rely on a magnetometer to correct the pole tilt for each measurement. A magnetometer is affected by metallic objects, like vehicles, iron fences and beams or even reinforced concrete, all of which are often found on construction sites. In order to provide accurate and reliable tilt values, Leica Geosystems developed an application-specific, powerful and lightweight inertial micro unit (IMU), which is built into the GNSS antenna. The real -time tilt compensation combines GNSS data with the IMU??s tilt and direction values. Different to magnetometer-based GNSS antennas, the GS18 T??s tilt compensation does not need to be calibrated and is immune to metallic object interference.
And how accurate are the measurements made with tilt compensation?
The accuracy depends on many factors. There is the accuracy of the GNSS position. If we look at the specified RTK solution, it is the same as with the GS16 ?? typically 8?ÿmm + 1?ÿppm (single baseline length) Hz and 15?ÿmm + 1?ÿppm (single baseline length) V. The accuracy of the tilt measurement is divided between the tilt accuracy and the direction of tilt accuracy. The tilt accuracy will typically be better than 0?ø12'00" and the direction of tilt accuracy typically better than 1?ø00'00". This means over a 1.8 metre pole length, the overall tilt accuracy is typically better than 20 mm at the pole tip with a tilt angle of 30?ø. This accuracy is comparable and most of the time better than using a conventional GNSS pole with a 20?? level bubble to make the pole vertical.
If the pole is tilted more than 30?ø, the accuracy of the tilted measurement reduces for two reasons:
- Tilt accuracy declines as the tilt is increased and the direction of tilt accuracy has higher impact
- With increasing the tilt angle, the antenna starts to lose track of some satellites, therefore reducing the GNSS position quality.
In any case, the position quality indicator in?ÿLeica Captivate?ÿshows the combined GNSS position quality and tilt quality, therefore representing the true pole tip accuracy.
Pole tip accuracy of 0.0175 metres, shown in Leica Captivate v3.0 on the field screen.
Other brands may also have a no calibration needed tilt sensor??
SHG
This accuracy is comparable and most of the time better than using a conventional GNSS pole with a 20?? level bubble to make the pole vertical.
I test drove one of these when they first came out and my Leica reps advise was unless you're fastidious about checking and adjusting your rod bubble just plumb the pole by eye and go.?ÿ?ÿ
South have their version due out soon. The Tersus is similar pricing to South G1.
Sweet. I understood that the G1 had a compensator as of a couple of years ago, but SurvCE wasn't at that time able to process it, so there wasn't much point having it.
I experienced the Data Collector telling me there is excess tilt, when the ebubble and the rod bubble are perfectly centered and the unit is on a bipod. This is shortly after a calibration routine has been completed. Two indepedent shots match exactly.
How is the Data Collector evaluating the GPS instrument's calculation of vertical?
results that are very close to plump measurements.
I resemble errr resent that remark.?ÿ
Reviving an old thread as there are now several other instruments with GNSS tilt.?ÿ Just curious what kind of accuracies these GNSS tilt measurements are getting with only half a sky and adjacent to a building.
?ÿ
Never one to shy away from tech development. For example, in my private practice, bought a Wang Laboratories 720C ($11,000) in 1970, bought the first Wild Di 10/T2 ($11,000) sold in the state of Florida by Florida Level and Transit in 1972, began GPS with a pair of Trimble 4000SSE's in the early 1990's, started aerial imaging using hexacopters in 2010, etc. etc.
However, I have never been intrigued in the least with the idea of leaning a rover rod over to take a shot. In early 2018, not long after they were introduced, I purchased a Leica GS18t. I can honestly say that I have never taken one shot with the pole purposely leaned over. Nor, have I ever explained to my people that the GS18t has that kind of technology built into it. I have seen others do it on Youtube, and I have (likely) a fair understanding of why, but it just doesn't do anything for me. Just recently picked up a slightly used Trimble R12, that it's owner was willing to take a beating on just for the pleasure of getting the new R12i(??). If you use tilt, and think it's the cat's meo I am happy for you. But, for anyone who doesn't have it and don't know how they can possibly go on another day, lighten up. Take it from this old codger, you don't need it...now do you(?). No you don't.
@i-ben-havin?ÿ Actually I especially don't need or want it. A lot of my shots involve the location of the antenna, not the point of the rod - the corners of covered parking is one example, and a corner of the top of a wall is another. I don't need an additional level of complexity, remembering to turn the feature on or off. When i want an accurate shot at the point of the rod I use a bipod.
@i-ben-havin?ÿ We have tilt compensation on two different instruments, both with full constellations - Not GS18.?ÿ I tested tilt, tested against buildings with half sky of SV's and know the accuracies.?ÿ I'm trying to find a project where we can use it and save money.?ÿ So far, tilt stays turned off.
Just wondering if anyone has taken a tilt enabled GNSS RTK and locate 4 corners of a building and meet survey standards for urban surveys.
@bruce-small I realize it's a personal thing, but I trained all my people to plumb the rod and make sure the bubble is centered, etc. I have not told my people about the tilt capability, mainly because (also, as you pointed out adds another level of complexity, and just 1 more way to introduce the possibility someone will likely take a crap shot) I believe it could lead to picking up a bad habit.
I would have loved to have the tilt when doing staking with GPS. Having to look at the bubble and the screen on my way to finding the point was always something that I felt awkward with. Sure, I made it work, but if I only had to look at my screen on the way to the point to getting the hub location, that would have shaved off a large amount of time and effort. Could still take a careful shot on the final location and/or on the hub...
I wish that I could have tilt on my prism pole. I have never worked with anyone that could hold a rod absolutely steady for every topo shot. I think it would increase real accuracy on common topos by an order of magnitude.
Been using a 12i for a couple months now and the tilt compensation is actually incredibly nice.?ÿ I think I've mentioned this before here but I thought the canopy tech would be the real lifesaver but honestly it's been the tilt compensation.?ÿ It was one of those things were I didn't realize how convenient it would be until I experienced firsthand how many fences I didn't have to shove upright, utilities I didn't have to lean the rod over or do an offset, pipe inverts I didn't have to balance the tip on, thalwegs I couldn't reach from the bank, and a dozen other scenarios in everyday topoing.?ÿ I don't mean to sound like a commercial but it really is a slick feature.
I don't mean to sound like a commercial but it really is a slick feature.
That's been our experience as well.
We had a lot of PLS naysayers (admittedly those who don't understand error propagation) who insisted the tilt function introduces grievous and permanent error into measurements, and forbade their crews from using it.
But after a lot of arguing (and some of us pointing out that buying a feature and not using it is ridiculous) they are finding that what you see is what you get for precisions, and with good measurement technique a compensated point is on par with a typical RTK observation.
There's also the Multitilt measurement method which significantly improves the final position and minimizes impact of the IMU standard errors.
I am anxiously waiting for an active track prism + IMU combo....
What does that mean?
Are you telling me you use a bi-pod for each topo shot? That sounds...slow.
@rover83?ÿ
Yes! Prism pole with IMU (you can keep the active track).
The problem is too much weight on the top of the rod
BUT...if you had a unit with prism, gps, imu...and active track if you must...and it all weighed less than the current rube goldberg devices they currently market as "hybrid"...then you would have a great tool.
The weight is a real issue, and perhaps they only way to fix that would be a dedicated rod with the battery at the bottom. Top heavy is not good.
Carbon fiber rod with batteries in the core, reinforced grip areas for DC, USB C plug in at the top and middle, run the prism, gps, and possibly the DC off the rod battery. The form factor would be much more stable...would also be a lot more expensive.
I realize that I am talking about something that would probably only be attempted by Javad...and he is gone. Makes me wonder if the current company will keep trying crazy stuff and trying to break the mold, or if they will try to go mainstream.
I'm sure you have the right idea, and I applaud you. I've just used a prism pole without tilt for taking all manner of shots since about the mid 1980's. Usually, I could manage to hold the rod steady/plumb enough for a total station to take the shot, and it would be ok for what we would be doing. Some monuments I felt it necessary, from time to time, to actually set up a prism/tribrach/tripod for the shot. Also, with the total station I never had to hold the rod plumb for several minutes to get the reading.
GPS is another matter. It usually takes me awhile to finish the reading, so I take along a bi-pod for shots on monuments. Edges of sidewalks, driveways, power poles, man hole covers, water meters, trees, edge of pavement, etc., etc. I just hold the rod as plumb as I can without worrying too much if it's out a few hundredths (we primarily only do boundary work).
But, yes...I am very s..l..o..w.......
