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Ben Harris's Discussions

UBLOX Neo-6P Logging Raw Data to Pixhawk - How to convert to Rinex

Started this discussion. Last reply by Sulu Oct 6, 2016. 17 Replies

Hi Everyone.I have a .log file from a UBLOX Neo-6P which is logging the Raw RXM data to the Pixhawk log file at 1hz.The question I have now is what is the easiest way to convert this to a Rinex…Continue

Geo-tagging Images in Mission Planner

Started this discussion. Last reply by Michael Oborne Mar 6, 2015. 4 Replies

Hi,I'm hoping someone can answer a couple of questions regarding the geo referencing function of mission planner. I have a fairly large dataset of some vertical imagery taken recently which I'm…Continue

Pixhawk Loiter and Guided modes don't seem to be working correctly

Started this discussion. Last reply by Justice Bentz Jun 25, 2015. 3 Replies

Hi,First post here so if this is in the incorrect place please let me know :)I'm flying a Skywalker X8 using the pixhawk autopilot and running mission planner as a GCS. Apart from the obvious…Continue

 

Ben Harris's Page

Profile Information

About Me:
Fixed wing Aerial Survey pilot and UAV controller.
Please tell us a bit about your UAV interest
UAV Controller in Australia
Hometown:
Brisbane

Comment Wall (5 comments)

At 1:53am on September 29, 2015, Darrel Maddy said…

Hi Ben,

Good to hear that you are using the M8T.  Can you tell me what is recorded by the pixhawk?  Does it log the full ubx information for reading in ucentre?

With my ground based differential system

(I use two of these https://www.optimalsystem.de/os.aspx?x=4116919&lg=en  )

I convert the ubx logs into rinex using rtklib (rtconv.exe). I then use the free (for L1 processing) Ashtech software:

http://ashgps.com/mirror/20130710/Land Survey/GNSS Solutions/software/3.80.8/index.html

I first correct the base to an IGS station (this gets me about 20cm accuracy for the datum) and then differentially correct the rover to the base (this has about 4cm accuracy).

My intention is to post-rocess the UAV M8T in the same way and then use the pixhawk logs to get the timestamp for each photo so that I can get a more accurate position. I have used the tagging in mission planner but with mixed results. I will need to explore other options once I have the correct log files.

Are you differentially processing now?

Cheers

Darrel

At 8:54pm on September 29, 2015, Ben Harris said…

Hi Darrel,

Thanks for your reply.

The pixhawk logs the raw GNSS data including psuedo-range and carrier phase onto into the log file itself. You can view this in the .log file, alternatively Michael Oborne has added the rinex conversion functionality to mission planner. If you load a dataflash log, and then generate a KML + GPX file, it will also generate a rinex 3.0 obs file provided the GPS has been logging the raw data.

I've then been running that against either CORS data, or a trimble 5700 base station in RTKlLIB for post processing. For previous flights I've simply been loading the 3DR log into Pix4d, as it accepts it, and letting it geotag the imagery, and using GCP's to clean it up. I would like to use two M8T's which I have, one as the base and log it's data as UBX, and then convert that in RTKLIB.

That's where I'm currently at a standstill. I have to figure out how to re-correct the photo centers based on the corrected DGPS data. I've been logging the rover data at 1hz, with flying speeds of 17 metres per second in no wind. I'm guessing I'm going to have to use some kind of batch file that interpolates the photo position based on flying speed, direction and acceleration. I know this gets done for full size aircraft travelling at 80m/s logging at 1hz, so I know it's possible. Alternatively I'm not sure if there is currently software available that already has this function.

I have to do some more testing on the M8T, but I was getting a lot of loss of lock indications from the 7P which I was using originally.

At 3:38am on September 30, 2015, Darrel Maddy said…

Dear Ben,

Many thanks - it looks like you are well ahead of me at present. I will order an M8T and get it working in my fixed wing. Its good to know that someone has already managed the rinex conversion in Mission Planner but the accurate tagging of images will be the issue.  I am currently using Photoscan Pro (I use a GPS camera in the drone) and GCPs  but sometimes the point clouds are, well let us say, a little unexpected. I am hoping better camera positioning will improve the outcomes.

If you find a cool solution to the image tagging please let me know. I'll keep you posted on my developments but this may take me some time!

Best wishes

Darrel

At 3:33am on February 29, 2016, Michael Tietze said…

Hey Ben and Darrel,

i have kind of the same issues but i think you both are already doing way better than i do.

I ve got the .obs data automatically created by MP but for postprocessing with rtklib I need the .nav data.

How or where did you get this data from?? 

The image tagging is a big pain in the ass for me aswell....did you find already a better way?

Cheers Michael

At 2:47am on October 11, 2016, Sulu said…

Hi Ben,

I've requested your friendship because I would like to ask you some information about the M8N implement on post processing purposes. My problem is that, using the M8N as secondary GPS I have no obs file on output.

Can you help me please?

tahnk you,

Marco.

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