Dear DJI,

As the developer of an application which utilizes SRT trajectory files for synchronized movie playback, I have two simple requests for improvement of the SRT file format.

1. Please increase the precision of the vehicle latitude and longitude from 4 to 6 digits past the decimal point (in degrees).

With only 4 digits past the decimal, the vehicle location can be up to 11 meters off from its true location. By increasing to 6 digits, this error would be reduced to about 0.1 meters (~1 foot). Although GPS accuracy is not 6 digits, having 6 digits of precision will still smooth the path of the vehicle when plotted on maps. See the screen capture below, where you can see stair-stepping, which is an artifact of low-precision latitude/longitude.

SRT data record showing only 4-digits of precision for lat/lon (11 meter precision):

00:00:04,000 --> 00:00:05,000
HOME(-118.0114,33.6636) 2017.08.05 15:38:06
GPS(-118.0065,33.6539,16) BAROMETER:12.9
ISO:100 Shutter:1000 EV: 0 Fnum:2.2



2. Please add the vehicle speed to the data record.

Since speed is currently not stored in the SRT data record, speed must be estimated based on sequential latitude/longitude waypoints. Given the low precision of these waypoints (see #1 above) the computed speed will vary unrealistically from second to second. Ideally the speed should be recorded separately into the SRT record, just like the ISO, EV BAROMETER, and other parameters. In Dashcam Viewer I have to perform a smoothing function to eliminate the peaks and valleys in the speed plot due to computation based on imprecise waypoints.

By adding these two capabilities (which should not be difficult because the speed and lat/lon are recorded to high precision already in the internal flight log), the precision and accuracy of flight reconstruction would be greatly improved.

Thanks
JFlyer3

Screenshot from Dashcam Viewer showing stair-stepping due to lack of lat/lon data precision.


Example uses of SRT files and Geotagging:

DJI drones are better than Parrot ones but, sometimes the best should learn from the others. See what the Parrot users can do: http://blog.parrot.com/2015/05/28/add-gps-overlay/

Thank you for your suggestions, I'll forward your requests to our engineers, they'll take them into consideration if it is possible.

I support jflyer3's request. I am having pretty much the same issues with the precision of the coordinates.

See: http://forum.dji.com/forum.php?m ... amp;fromuid=1077205

Sorry, duplicate post

@jflyer3 Did you have any luck getting in touch with DJI? Or did you find the accurate data you were after somewhere else? Thanks

Negative, @0Kajuna0, I have not heard anything back one way or the other from DJI. Would be nice if they could respond to this thread.
That said, I don't have the latest firmware on my Mavic Pro so I can't double-check the SRT file to see if the change has been made. If someone has an SRT file created using the latest MP firware, perhaps they could post a few lines here.

With firmware 0.700, you can see in Dashcam Viewer, that the aircraft's route is  rough and the speed graph is very noisy due to interpolation of poor quality lat/lon points to derive speed data.  

jflyer3 Posted at 2018-2-5 18:22
Negative, @0Kajuna0, I have not heard anything back one way or the other from DJI. Would be nice if they could respond to this thread.
That said, I don't have the latest firmware on my Mavic Pro so I can't double-check the SRT file to see if the change has been made. If someone has an SRT file created using the latest MP firware, perhaps they could post a few lines here.

You can also do amazing things with  Racerender . I synced my flghts with airdata site and exported the kml (or .csv, don't remember)  file. Next you can use racerender to import the movie created wth your drone and the kml or csv. Next step is sync the data file with the movie, add controls to the movie like speed, heading, pip-map etc. After this racerender can export a new movie with all the controls on screen. Hope this helps.

jflyer3 Posted at 2018-2-5 18:22
Negative, @0Kajuna0, I have not heard anything back one way or the other from DJI. Would be nice if they could respond to this thread.
That said, I don't have the latest firmware on my Mavic Pro so I can't double-check the SRT file to see if the change has been made. If someone has an SRT file created using the latest MP firware, perhaps they could post a few lines here.

Sorry, @jflyer, I somehow missed your reply. I don't think this forum sends notifications when you @ someone. Does it?

I do use the latest firmware on my Mavic Pro and precision has not improved.

I created a simple web app for visualizing the data. As you said you can get a rough idea of paths and speeds by smoothing data, but precision is nowhere to be found: https://forum.dji.com/thread-140031-1-1.html

Is increasing the precision even possible?  The GPS onboard a DJI is not capable of subfoot precision, at least not without other GPS data and post processing.  Increasing the precision would not increase the accuracy, it would just make the number longer.  It would have the same effect as just adding zeros to the end of the lat/long.

craig32 Posted at 2018-6-29 14:33
Is increasing the precision even possible?  The GPS onboard a DJI is not capable of subfoot precision, at least not without other GPS data and post processing.  Increasing the precision would not increase the accuracy, it would just make the number longer.  It would have the same effect as just adding zeros to the end of the lat/long.

There is additional accuracy in the GNSS position fix and DJI is not utilizing it in their SRT file. The additional digits can be seen if the trajectory data is exported in other formats. With 4-digits shown, precision is about 25 meters. Even a cheap GPS receiver can yield accuracy better than that. One more digit would knock this down to about 7 feet.

@craig32 : Is increasing the precision even possible?

Look at the values ​​stored in the exif photos ...

Everything is there !