Thanks for the answers, but none answer me if Chinese receivers are worth the effort.
Maybe they have changed their confidence level from 99.9% to 90%? That's why they give easily fixed soloutions?
Chinese receivers are worth the effort
Yeah, sure. ?ÿHappy with mine.
Maybe they have changed their confidence level from 99.9% to 90%? That's why they give easily fixed soloutions?
Pretty difficult to debate conspiracy theories.
I have read how IMU works and i Can not trust them 100%.
I would hope that you're not trusting your GNSS results 100% either...
We currently have about ~20 R12i receivers in the field. We have found that RTK+IMU solutions are generally repeatable to ~3-4cm under typical conditions. The IMU adds about ~5mm of positional error (RMS) plus less than 1cm if tilt is below 30 degrees. That's about 15mm on top of the ~2cm that is common for RTK, so it generally lines up with the specs.?ÿ
I wouldn't go with a particular manufacturer based on a single feature, or the fact that a single item does slightly better than a competitor in one area. Other things are at least as (I would say far more) important for productivity, such as how intuitive the field software is, mechanisms to push data to/from the office, and ease of post-processing. It's better to evaluate the whole package.
From your experience if an IMU ads some cm error is better to work with IMU closed when not need it?
I used to be able to guess what the options were by price and full part number, but I can't do that anymore. I have to connect to a head with a serial cable, put in passthrough mode and then use PPP to connect to the internal engine and poke around. WinFlash reports 5.46 for devices with 6.06, and the web interface matches winflash.
Dear, please, please, tell me more, how exactly? They gave me a MaxPro code, but I don't know how to connect WinFlash to the board for my G1+ with BD990 ... Or i can to see WEB of BD990 ??? Thank you !
I shot points very nervously under heavy canopy, as we were staking line my checks on line points were visual. However, I wanted the end points (monuments) to have better checks. The second worst location was a 1/4 on the west end of a E-W center section line. I had originally located it 6 months prior, located it a second time that same day within .02x.04'. Then six months later located it again with the same accuracy from a different base point. Other monuments along the property line were also located with similar results, some had been visited in the original search from 6 months before. Only one required extra surveying, it was against a large yellow pine and had to be set from offsets.?ÿ
I've done many surveys in canopy with my R8-2's and have good luck with them. I agree, the displayed error on the DC screen is not something to be treated as gospel. But second locations lately have been changing my mind somewhat. They seem to concur more with the screen than before.?ÿ
I'm not about to state that bad fixes are a thing of the past, but error-trapping is causing them to be very rare.?ÿ
Presume you are checking against previous surveys or conventional surveying which is known to be tight as two GNSS shots in canopy/ multipath/challenging conditions I find can still be giving you the same result twice but against tight traverse work is not right. I.e expect two 30 epoch rtk GNSS shots in open to be within 10mm at 95% CI but in cover/next to tree/utility pole you can get the same repeatiblity but the result is biased by the obstruction ~20mm. Have observed this with different brands of gear (including the magic Javad box & no I don't think it was better than a top end Trimble/Lecia in canopy when checked against total station traversing known to be reliable) and making sure to use different satellite geometry. I'm in the southern hemisphere but still using the same satellites. Canopy here is usually pretty dense, as in no sunlight filters through, not gaps between trees.
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If you have verified and still getting those results I take my hat off else suggest some conventional checks to be sure.
I'm using a 12i at the moment.?ÿ I think the IMU is great, but that canopy busting stuff they talk about seems extremely hit or miss (mostly miss).?ÿ I spent all week working in leave-less trees and I couldn't get very good accuracy anywhere, even in the lightly wooded areas.
@bstrand?ÿ
Possible to define the accuracy you were after but couldn't get, and if it was just CQ's or some higher confidence interval? Also distance from base receiver or NRTK?
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Think it's super helpful in these discussions to have actual numbers else some who work to 10-20mm think GNSS no good in canopy whereas others only after 30-50mm think its fine (and some others claim their flavour still gives the lower figures in any canopy).
Yeah, I really should have more specific data than "sometimes it sux and sometime it's gud!".?ÿ ????
Anyway, I think for the project I've been working on lately we have a .06 residual tolerance set in the equipment with 2 sigma confidence, and this is what I seem to have trouble hitting in the field.?ÿ These are just run of the mill topo shots in varies degrees of canopy so it's unlikely any particular area will be revisited unless something looks completely whacky in the office.?ÿ Also, we're using a base and rover setup with an external radio even though we're working less than a mile from the base.
@lukenz?ÿ
Nah, I'm good, check-ins to points months apart that check within 8mm on the boundary of a large parcel is the chef's kiss. Chasing ghosts is against my nature.
I think the IMU is great, but that canopy busting stuff they talk about seems extremely hit or miss (mostly miss).?ÿ I spent all week working in leave-less trees and I couldn't get very good accuracy anywhere, even in the lightly wooded areas.
You are turning the IMU off for under-canopy shots, right?
I wasn't, no.?ÿ But the IMU on the receiver I'm using seemed to have stopped working recently anyway.?ÿ I spent some time yesterday trying to do a calibration on it but it didn't seem to work.?ÿ Anyway, are you suggesting the IMU causes problems in canopy??ÿ if so, this is the first I've heard of it.
I also noticed that if IMU of the R12i is on under heavy canopy measurements are not so precise. Also check it with total station measurements!
I wasn't, no.?ÿ But the IMU on the receiver I'm using seemed to have stopped working recently anyway.?ÿ I spent some time yesterday trying to do a calibration on it but it didn't seem to work.?ÿ Anyway, are you suggesting the IMU causes problems in canopy??ÿ if so, this is the first I've heard of it.
I also noticed that if IMU of the R12i is on under heavy canopy measurements are not so precise. Also check it with total station measurements!
IMUs, by definition, require some movement to maintain orientation/heading, but the GNSS antenna solution, by definition, will not be able to converge unless it is stationary. There's a trade-off when working with the IMU enabled.
The R12i documentation specifically recommends that IMU compensation be disabled when in difficult environments:
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