Best configuration just "for measure"

Problem 1. The area is about 300 km away from 2 permanent stations belonging to the EUREF Permanent GNSS Network. So no fixed GNSS station is available.

Problem 2. Its impossible to prolong the operations “for hours” in order to accurately obtain the coordinates of the point where it is located.

If my goal is just to “measure”, can I simply position the station at any point and go around with the rover measuring relative distances (in meters) and relative height differences (in meters) between the station and the rover ? Even in real time ?

What I want to get is just a CAD drawing with the station at [0,0, some elevation] and all the points around detected by the rover with the exact distance (in meters) and the exact elevation difference (in meters) from that station.

How ?

With what precision (on both X,Y and Z) ?

Hi @birdofprey,

Would you mind specifying the receiver you’re working with?

The rover’s position in RTK will be centimeter-level accurate relative to the base. The base, in its turn, should be placed accurately for high absolute accuracy. You can use a PPP technique for that.

You can follow the Base and Rover setup guide to configure receivers for your task.

Hi @anastasiia.iusupova

My need is to measure GCPs supporting the survey flight with the drone.

At the moment I don’t have any GNSS equipment and I use an old laser total station.

What I would like to do is position the base anywhere and start measuring the GCPs with reference to that base (which in my reference system becomes the origin).

In my work I do not need geo-referenced GCPs. What interests me are distances, heights, areas and volumes. The accuracy of the cm is more than enough.

The final result should be a simple CAD plan with the 0 point (station) and the points detected by the rover in x, y, z coordinates with reference to the origin (station point).

Hi @birdofprey,

I’d recommend checking the Reach RS2 Survey Kit, containing the base and rover.

We have a guide describing the ground control points placement workflow, you can find it here: Placing GCPs in RTK mode.

You can export the coordinates of the collected points in CSV, DXF, GeoJSON, or ESRI Shapefiles formats to your CAD system.

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Hi @anastasiia.iusupova

I have read all the guides very carefully and here is what I would have in mind to do in order to get the best compromise between initial investment and final result.

I would like to buy only 2 Reach M2, 2 antennas and 2 power banks.

On the field, I place the first Reach M2 on a fixed (unknown) point and start recording data from the satellites. After about 10 minutes, I also turn on the other Reach M2 and go around positioning it on the GCPs that I want to measure. All for about 30 minutes.

When I get home I download both logfiles and process them in PPK and so I got the relative coordinates (referring to the base) that I can use to scale the photogrammetric flight.

What do you think about it ?

Its doable. Are you going for absolute or relative accuracy with your drone?
If you spend around 2 hours or more, your should get fairly ok absolute coordinates from PPP, you would still need to apply a relative shift when doing PPK too.
Have you considerd trying PPP flight ?

I just need relative accuracy.

What you mean with “PPP flight” ?

Hi @birdofprey,

As Tore mentioned, this setup should work fine. You can use Reach M2 for your task.

Please note, these receivers don’t have a moisture and dust protection, so it might be needed to use a protection case for them.

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Use a singel reciever and submitt for moving observation

Facts about CSRS-PPP

CSRS-PPP post-processing can be done in two modes: Static (“fixed” GNSS receiver) or kinematic (“moving” GNSS receiver).

  • Static produces one corrected averaged single point.
  • Kinematic produces a corrected track.

Output coordinates can be in either NAD83 (CSRS), the standard Canadian national reference frame, or the global ITRF. Users need to select the system that is the most appropriate for their purpose (see Reference frames).
https://www.nrcan.gc.ca/maps-tools-publications/tools/geodetic-reference-systems-tools/tools-applications/10925#ppp

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@anastasiia.iusupova

I certainly prefer M2 because having dual frequency is important in many “not optimal” scenarios. But I think the M2 is not yet avaible… correct ?

@TB_RTK

Does it only apply to Canada or the whole world ? How is it possible that there is a way to have centimeter accuracy EVERYWHERE with just a single receiver and this system is not widespread and advertised ?

Is there any software that allows you to process data on your PC, with this system, without relying on third party processing ?

Yes

It is widespread. NrCan and other system has been around for a long time.
Its been mainly dual reciever service with high cost gear and not something affordable to everybody.
But now, with Emlids affordable single and now multiband recievers this is available to “everyone”.
PPP has some limitations. Postprocessing time, you have to wait to get the most accurate products. Available satellite system and update rate.
I am still experimenting with rapid/final solution, distance between epoch and the interpolation.

Edit. Forgot distance to base station with kinematic PPP.

I use NrCan, RTKlib and Qgis

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According to the information from our site, Reach M2 is available now. You can also contact our dealers to purchase a device locally.

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@TB_RTK

I wouldn’t need high precision. Even 10 cm of error (on Z) is fine. I could also wait for the next day.

But spending 2 hours for surveying just 3-4 GCPs… perhaps it is better to spend 10 minutes to assemble a base station on the field…

Sounds like you should look into kinematic ppp, i cant say what accuracy you will get but might be enough for you. kinematic flight also depends on the numbers of refrence station with common satellite in view with the flight and distance to station from the flight.
This setup needs more testing and would be great if more users could share their experience

Not sure you have an option here (for absolute position). If closest refrence station is 300km away, you are left computing a VRS for your self, hire a VRS service, use min 2 hour static ppp, or start recording your base station at arrival and hope your job last longer then 2 hours for it to be used for static ppp, then you could ppk the flight and apply shift later on.

Edit: The above is for absolute position.
For relative measure you should be fine with a much simpler setup. Like the base/rover setup

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Since in 90% of cases I’m only interested in the relative measures, I believe that using a base (on any point) and a rover (in PPK mode) is the best option.

Furthermore, in 10% of cases in which I need absolute positions, I can place the base at some topographically known points (far some Km) and survey with the rover and process everything in PPK.

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