simplertk2b for surveys: how to ?

Q&A forumsimplertk2b for surveys: how to ?
birdofprey asked 4 months ago

I work in the field of topographic surveys using drones and I’m looking for a simple and low-cost solution for measuring some points on the ground (the famous Ground Control Points) to which to “hook” the point cloud obtained from the flight of the drone.

I don’t care that these points are geo-referenced. Im just interested in “measuring” relative distances and relative height differences between these points in order to construct a “skeleton” with which to correctly scale the 3D model obtained from a drone that does not have a precision GPS on board. I’m not also interested in high relative precision. Even an error of 10 cm (even on Z) is fine.


I believe that the “simpleRTK2B – Starter Kit MR IP67” can do for me because the distances I work on never exceed a few hundred meters. I also state that I have read “MR / LR kit hookup guide” on the site.


What I would like to understand is how to do all this in practice. I can feed the base with a power bank connected via USB. The rover can feed it the same way. But where do I read the measurements ? How do I connect a tablet if the USB is used for power ? What application should I use to read and record the points I measure ? During a survey in the field it is inconvenient to use a PC with u-center. How can I do everything on a smartphone or tablet ?

 
Thank you.

6 Answers
birdofprey answered 4 months ago

What I would like to understand is how to do all this in practice. I can feed the base with a power bank connected via USB. The rover can feed it the same way. But where do I read the measurements ? How do I connect a tablet if the USB is used for power ? What application should I use to read and record the points I measure ? During a survey in the field it is inconvenient to use a PC with u-center. How can I do everything on a smartphone or tablet ?
Does anyone give me some initial advice ?

skypuppy answered 4 months ago

Try putting the base unit actually ON one of the control points and setting it manually to that known position.  No relative adjustments needed in post processing then.

skypuppy answered 4 months ago

You’re not going to get cm level accuracies without base/rover config working together.  If you can get ntrip data to the base you’ll also have the actual locations within your allowed error bar as well.

birdofprey answered 4 months ago

@skypuppy
There is no doubt that I need a base and a rover (I do not have access to correction services or nearby public GNSS bases).
Since I do not need a geo-referenced topographic survey, I believe that the base can be placed at any point and its coordinates can be those of the single (approximate) GPS averaged reading.
So I can place the base, power it with a power bank via USB and that’s it. At this point I have to go around with the rover, put it in the points to be measured and read the coordinates fixed with the correction sent by the base. The problem is, if the rover’s usb port is occupied by the power bank, how can I connect a smartphone on which to read and memorize the measured points ? Fixed this problem, with which app can I do this ?

clive1 replied 4 months ago

There are two USB ports, power the device with NOT the ZED one.
Power via the NORTH end USB, which connects to the FTDI/XBee

birdofprey replied 4 months ago

From the documentation I read:
1) USB GPS port
2) XBEE USB port

What you say is that I have to connect the power bank to the XBEE USB port (J2 on the board) and connect a smartphone to the USB GPS port (J1 on the board). The antenna instead goes into the J3 connector. All correct ?
Once this is done, should the card receive data from the satellites and also receive corrections via radio from the base and show the result (latitutide, longitude and ellipsoid height) in an app installed on the smartphone. Correct ? Which APP is compatible with this and works well ?

clive1 replied 4 months ago

>>What you say is that I have to connect the power bank to the XBEE USB port (J2 on the board) and connect a smartphone to the USB GPS port (J1 on the board). The antenna instead goes into the J3 connector.
I’m, not sure what the alternative connection for the GNSS antenna would be, but yes GNSS antenna to J3, power pack to J2, USB connectivity for ZED to J1

In default configurations the ZED should output NMEA data usable by most apps, good perhaps to 2cm

>>Which APP is compatible with this and works well ?
I’m not doing smartphone/android integration work. If I were look for a coder I might check the local high school or community college. Check the app store for software doing GPS data logging or mapping type functionality. Figure farming, GIS, survey, etc.

skypuppy answered 4 months ago

There may be inconsistencies in apps on the phone, due to the high-precision the F9P can put out (that’s where we get the 2 cm precision.)  You’ll just have to shop for an app that can handle it; else you will only get the 2-9 meter precision, AIUI.  I’m not even sure the NMEA strings allow so many places after the decimal point.

clive1 replied 4 months ago

>> I’m not even sure the NMEA strings allow so many places after the decimal point.
Early NMEA had 4dp, uBlox has 5dp by default, I’ve used ones outputting 6dp for well over a decade. I think you can expand the precision using UBX-CFG-NMEA
There are a few NMEA decoders/parsers written by half-wits that have issues, they often use 32-bit floats also, which will have huge jumps at the extremes as you approach +/-180 degrees. Apps coded by reasonably competent developers should be fine.
5dp at the NMEA level is roughly equivalent to 7dp in UBX (decimal degrees). The HP (High Precision) versions expand that to 9dp

birdofprey replied 4 months ago

Sorry but I’m very confused. I need help.
When I position myself on the point with the rover, after the RTK fix from the base, I would like to read (and memorize) only these 3 things on a tablet or smartphone:
1) latitude
2) longitude
3) ellipsoidal height
Is it possible to get this with ardusimple? How?

birdofprey replied 4 months ago

Up.

Is there an optimal configuration and an app (even for a fee) to achieve this without too much effort ?