Phantom 4 RTK - How to PPK?

[Macenroe82]

Hello everyone,

Im pulling my hair out over here trying to figure out how to get the P4 RTK to work properly.

I got tired of the error " Weak RTK signal - cannot take off" so I flew without the D-RTK2 base with PPK in mind.
Im in a remote mining location - well out of cell range.

I have a Trimble R10 Base station, that I set for logging.
The base is static and is used daily for RTK surveys on our mine site.
The Trimble collected logging data for 1 hour before I sent up the P4RTK.
I turned off RTK in the DJI GS app.
Sent the drone up and began my flight mission.

The flight consisted of 20 flight lines, about 800-900 meters each.
I had to do 4 battery changes during the flight, so I have 4 folders containing the imagery and the phantoms survey files.

Now, this is where I need some help.

I got my .to2 file from my Trimble base. I converted it to Rinex and got my .19o (obs) and .19n (nav)
I took the PPKRAW.bin file from the drone, converted it and got ppkraw.obs and ppkraw.nav

I opened RTKPost and in the RINEX OBS: Rover field, I brought in the PPKRAW.obs
in the RINEX OBS: Base station I brought in the .19o
and for the RINEX NAV field I brought in the .19n

I executed and got the PPKRAW.pos file.
When I plot that file, it is all over the place.
as can be seen below:

Then I converted my .pos file and the Timestamp.MRK into the Aerotas spreadsheet to create an image tag file.
But its not working for me.

Is there a step by step document around that provides the PPK workflow?

I would like to use the D-RTK 2 base but the one and only successful flight I had, the images were all tagged with the wrong elevation - the geoid height above the WGS 84 Ellipsoid wasnt taken into account.
I tried setting the base up over a known point and then going into the advanced settings on the DJI GS app to add the proper lat and long and elevation in decimal degrees, but I only get an error saying im more than 50 meters away from that coordinate.
Which is incorrect. Its a GCP that is used to tie in our projects.

Anyways, any help would be greatly appreciated!

Thanks

[MichaelL]

What version of RTKLIB are you using?

@Macenroe82

I opened RTKPost and in the RINEX OBS: Rover field, I brought in the PPKRAW.obs
in the RINEX OBS: Base station I brought in the .19o
and for the RINEX NAV field I brought in the .19n

You might want to try the P4RTK NAV file.

@Macenroe82

I would like to use the D-RTK 2 base but the one and only successful flight I had, the images were all tagged with the wrong elevation - the geoid height above the WGS 84 Ellipsoid wasnt taken into account.

In RTKPOST did you enter the known coordinates and elevation for the base in the Positions tab?

@Macenroe82

I converted my .pos file and the Timestamp.MRK into the Aerotas spreadsheet to create an image tag file.
But its not working for me.

I typically create a GPX file through GeoSetter and retag the photos so you don’t have to do any manipulation in the processing software. Does the P4RTK create events in the POS file? It would show up as a separate file being that you will have one full-track without events and another with them. If not then I would contact Aerotas.

@Macenroe82

I tried setting the base up over a known point and then going into the advanced settings on the DJI GS app to add the proper lat and long and elevation in decimal degrees, but I only get an error saying im more than 50 meters away from that coordinate.

This happens quite allot when comparing averaged coordinates between different receivers. This is why allot of people like to use CORS or VRS services, but I have never used them myself and have had no need to. How long was the D-RTK2 setup before you entered the coordinates and made it active? Does your site have a localization?

Hopefully someone can chime in that has a more similar workflow to yours, but here is a thread by @GregO that may help.
How To - PPK Processing with RTKLib (Phantom 4 RTK)

[Macenroe82]

Thank you for the reply,

I’m using RTKLIB version 2.4.3 emlid b28.
I’ve been using this version since it came out. I have an Event 38 Fixed-wing that has an Emlid GPS.

You suggest using the drones Nav file?

• I just assumed it would be the same process for PPK with the P4RTK as it is with my Event E384 Fixed wing. In this process, we use the base stations .nav file.

Yes, the coordinates are in there for the base - as mentioned I go through this process for PPK with the fixed-wing.

The P4RTK creates an eventlog.bin file.
I assumed the timestamp.mrk file would be the precise millisecond the camera takes the photo - like a hot shoe.

I allowed the D-RTK2 base to sit for 10 minutes before linking.

Thank you for the PPK link, I will check that out now!

[MichaelL]

Please try RTKLIB b33a.

RTKLIB Code: Windows executables

Unfortunately DJI’s files are just about sandboxed and conversion is usually involved. Mapped fields don’t line up with many softwares. There’s a whole host of files that can be imported into Geosetter as GPS tracks, but I do not see the MRK. There is a BIN, but like I mentioned I do not know if they are mapped correctly.

I am using Emlid hardware to PPK and was told to use the drone NAV and have never had any issues, but it may be different with the P4RTK.

10 minutes is good on the satellite collection pre-use.