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High Frequency Continuous Points
Posted by mov_hp on December 30, 2021 at 8:10 amA question about Trimble Access. Can one collect data at high frequency with Access? Since the receivers are mostly 20 Hz, but what is the highest frequency one can collect continuous points with Access? Any other software that can do this?
Sincerely
john-hamilton replied 2 years, 3 months ago 6 Members · 14 Replies- 14 Replies
I believe 0.5 Hz is the “fastest” rate you can collect with an R10. When running mobile LiDAR we collect static positions at 1 Hz. File size gets very large at these rates.
- Posted by: @mov_hpCan one collect data at high frequency with Access? what is the highest frequency one can collect
Why do you want or need to collect anything faster than the equipment already does now?
In GPS, the more data collection in less time doesn’t provide better results.
The satellites need to move across the sky to change positions to create the solution on the receiver/DC.
Recording data for the most minute change only provides more noise and potential for poorer data overall.
@jitterboogie While probably not directed towards me…We collect at those rates in order to process the trajectory of the mobile lidar unit. The mobile lidar unit has 1 to 2 GNSS reeceivers on it that are moving, quickly. The base data captured at 1 Hz enables the trajectory to be processed at every second’s location of the unit. If we collected at 30Hz the vehicle will have moved, well possibly 100’s of meters.
Understood. I remember your posts regarding the mobile LiDAR for road surface collection.
I was just curious about their own process to elucidate the usage, and maybe even initiate a discussion about the collection hardware and proprietary software for the cause.
LiDAR and InSAR are special animals and usually have pretty awesome robust supporting software that you can utilize and hit the ground running without the other solution seeking to get products or software not designed or intended for that area.
I’ve been down lots of rabbit holes. Some of my own and several of others. My new role is a great crossroads of how to avoid time wasted by being creative and productive. It’s a fantastic and sometimes frustrating place and enjoyable none the less.
Just rambling and curious.
On the day before the last day of this year.
- Posted by: @jitterboogie
enjoyable
This is key.
It’s the ultimate goal.
@jitterboogie Yes, InSAR is the wave of the future. The capabilities are mindblowing. For those watching the clock today…Start here:
THen head over to UNAVCO and NSF site to explore. Very cool stuff happening
@stlsurveyor you mean 2 Hz i.e. 2 points per second or 1 point every 0.5 seconds? I was wondering what is the use of having 20 Hz (20 points ps) capability if the software can only log 2 points per second. Thought we could map terrain over large areas more accurately while still driving quick.
Sincerely
I’ve been using Unavco since about 2005
And worked on a DARPA InSAR IED detector proof of concept aerial platform project.
You ain’t kidding.
Future is rolling by for the plumb bobbers.
????
@mov_hp Copy that, but at some point moving quick and only using GNSS you would reach the point of tool limitation. At 20mph you would get a shot every 30 feet. I guess you could play with Access some. You can set it to store a point based on movement under continious topo. But there will be a point where the software cannot keep up. I’ve used that workflow for topo collection in a bean field as I am sure everyone has as well, but driving across a bean field at 20mph wouldn’t be much fun.
@stlsurveyor I spoke to some surveyors using Trimble. Access also fails to log positions at regular interval if one drives quick. We go quick sometimes on oil sites. Fortunately we have Toyotas here to negotiate terrain. We can go much quicker to finish the job faster. But since the software does not support more than 2 hz logging then what is the point of having a 10 hz or 20 hz receivers. This seems just bumped up specs to look nice on datasheet. What do you think?
Sincerely
@mov_hp In my professional opinion I think the approach you are trying with GNSS receivers at high speeds across rough terrian is not the best method to collect reliable survey data. If you are in that much of a time constraint, I would suggest you us abandon GNSS approach and use a UAS to fly the site. That would be a much better method to cover the site quickly and would yeild results that can create a decent DTM. Even with a cheap OTS DJI drone you can fly 40 acres in an hour or so. You would just need to shoot in a handful of control points and a few check shots.
- Posted by: @mov_hp
I was wondering what is the use of having 20 Hz (20 points ps) capability if the software can only log 2 points per second. Thought we could map terrain over large areas more accurately while still driving quick.
I’m confused. This isn’t a Trimble issue, it’s a radio issue. RTK radio uplink rates are rarely faster than 1Hz, no matter the manufacturer. Anything faster than that running RTK and it’s likely just interpolation so it’s not going to be much better anyways.
Posted by: @stlsurveyorIn my professional opinion I think the approach you are trying with GNSS receivers at high speeds across rough terrian is not the best method to collect reliable survey data. If you are in that much of a time constraint, I would suggest you us abandon GNSS approach and use a UAS to fly the site. That would be a much better method to cover the site quickly and would yeild results that can create a decent DTM. Even with a cheap OTS DJI drone you can fly 40 acres in an hour or so. You would just need to shoot in a handful of control points and a few check shots.
This is my opinion as well. If you need fast collection over large areas remote sensing is the way to go.
If you are really hellbent on doing it from the ground at a high data rate, forget Access and just set up a “base” receiver in the project area, start logging at 20Hz, then start logging at your “roving” receiver at 20Hz. Collect enough stationary data at the start and endpoints (~10 minutes) to get a good fix, then drive the site. Postprocess and force kinematic in TBC to get your trajectory (or points if wanted). If you have good satellite conditions throughout your project area (which you should anyways if you’re trying to use RTK) you should get plenty of data.
(Should add that if going this route, you need to make sure you are downloading and then deleting the data regularly. 20Hz is a lot of data and will quickly fill up even the large memory storage on current receivers. Had a few folks ignore the warnings and lose large chunks of data because they filled up storage at the base halfway through their day.)
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman @stlsurveyor I think you mean if you collected at 0.033 Hz you would miss a lot, that means every 30 seconds. 30 Hz is 30 times a second.
What everyone should understand about mobile lidar is that it uses an IMU collecting data at something like 200Hz or more, it uses the 1Hz GNSS data to correct the IMU for drift. And it uses the IMU data to correct for loss of lock on the GNSS and to interpolate the position at a more frequent interval than the GNSS is capable of.
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