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Pix4D Mavic 2 Processing Issues

Best Solution (as of the time of this edit):  Upgrade to Pix4D 4.4.9.  As of the time of this edit-entry it isn’t part of the automatic update but is available at https://cloud.pix4d.com/download/

Hey Guys,  

I just got the new Mavic 2…takes great pics…but I’m having issues processing these scenes.  The GPS coordinates showing in the pictures actual files are correct…but they translate incorrectly in pix 4d

Below are the pix4d results from processing the Mavic 2 photos…the red are where the software says we droned…the blue is where we actually droned.  The differences is approx 1.6 miles

The GPS coordinates on the actual file are correct but they translate incorrectly in the pix 4D software…the second picture shows what the true

Additionally the Moasaic is having blur/overlap/double-vision issues as shown below:

 

Any Advise?

Are the input and output coordinate systems the same?

About the mosaic, are there any gpc or mtp used?

The input (gps meta data from the file) is correct…
the output (pix 4d interprets these coordinates is incorrect)…these two are put side by side in the second pic from my post

 

 

the mosaic output (what pix4d is additionally incorrect)…the output is shown in the first pic  from my post

 

 

gpc used was wgs 84 (egm96)…this is kind of visible (low rez) in the bottom right corner of the first pic from my post

Hello Jack,

Would it be possible to upload three images to see what is going on?

Anyway, it seems that something is wrong with the geotags, the height is 115068470.9 meters.

What is the output coordinate system you have selected?

Thank you very much.

 

Here is a link to 3 of the source images for this drone project:  https://1drv.ms/u/s!Aoq26ZQwst6yeZSQ1rn_8GKwE9U

Below is the view of the ouput coordinate system

Although you are correct the altitude is wrong from the Mavic 2…we ran a test and stripped the jpg files of that crazy altitude reading in the EXIF field and pix4D is still translating the remaining GPS coordinates incorrectly to about the exact same splot as before.  I don’t think this issue is related to the altitude.

Hello Jack,

I have imported the images in Pix4D and compared the coordinates of the same area in Google Earth.

They are in the same place.

Google Earth:

Coordinates shown in the lower right corner: 30º16’ 22’’ N 97º15’39’’

Pix4D:

Coordinates of the same point approximately: 30.27969455 N 97.26101831 W

 By looking at the file properties, the coordinates are also very similar:

 

If you flew in the area that you mention in the first post, I think that either there is something wrong with the geotags or maybe they are not given in WGS84.

Regards.

Correct…when I convert the coordinates from the file (i.e.right clicking, properties, viewing GPS section the details tab) 

 

30+(17/60)+(48.2169321285765/3600) = 30.29672692559127

and 

-1*97+(16/60)+(40.3898343142937/3600 )= -97.2778860650873

So when I plot those calculated coordinates I get the following location which is where we actually flew (on highway 290)

So we think the geotags in the file are correct.  The altitude is way off but that doesn’t seem to have any bearing as we ran a test by stripping the files of the altitude exif data and PIX4d had the same exact wrong result with those modified files.   

And so I’m curious about the comment: “maybe they are not given in WGS84” and what the implications are of this regarding how to rectify or compensate for this issue.

Hello Jack,

After some investigation, I found out what is going on and the reason for your displacement or the reason why Pix4D is locating the images far away from the place where they were really taken.

I have opened the EXIF data embedded in your TIFF files.

You can also do it by using the free exiv2.exe application ( http://www.exiv2.org/download.html )  or you can also use this website and drag any image ( http://metapicz.com/#landing ).

If you do that, you will see that your images have two places where the GPS coordinates are stored and they are different:

1.XMP tags

Xmp.drone-dji.Latitude XmpText 11 +30.2967378
Xmp.drone-dji.Longitude XmpText 11 -97.2779208

They are coming from your DJI drone and they show you the right coordinates,  where the flight was really taken, which is to say, over the road.

 

2. EXIF tags:

Exif.GPSInfo.GPSLatitudeRef Ascii 2 North
Exif.GPSInfo.GPSLatitude Rational 3 30deg 17’ -13.140" 
Exif.GPSInfo.GPSLongitudeRef Ascii 2 West
Exif.GPSInfo.GPSLongitude Rational 3 97deg 16’ -20.967" 

This is the place where the coordinates are usually stored and where Pix4D takes them from.
If you do the conversion from Degrees,Minutes and Seconds to Decimal degress , what you have is:

30.28698°
-97.27249°

Which differs in more than kilometer from the coordinates from the XMP tags.

That means that the drone is storing two different coordinates for each photo and they are far away from each other.

In addition to that, the seconds have a negative sign, so Pix4D is subtracting that amount of seconds to the minutes, so what Pix4D is really taking is:

30 deg 16’ 46.86"

97 deg 15’ 39.033"

Converted into decimal degrees:

30.27968340

-97.26084254

Which is the place where the images are located in Pix4D’s map view.

 

Are these TIFF images generated automatically from the DJI or it generated JPG and they were converted into TIFF?

You can find more information abot the EXIF and XMP information read by Pix4D here.

If you want to use the real position, they must be stored in the EXIF tags and not in the DJI XMP tags.

 

I show you in Google Earth the differences between the three positions:

It would be good to know why the drone is storing two different sets of coordinates which are more than 1 km away, and why the seconds are stored with a negative sign. Maybe you can contact the drone or camera manufacturer.

Regards.

 

 

Many thanks for looking into this and pointing out the tag issue…   Although i’m confused about your question…“Are these TIFF images generated automatically from the DJI or it generated JPG and they were converted into TIFF?”

I’m confused about the source of the TIFF files you are using.  In my original post as well as all my subsequent post I’ve been referencing JPG files which is what the drone is outputting.  Additionally, the three files in the ONEdrive link I posted are JPG.

Hello Jack,

You are right, the images are JPG, not TIFF. Sorry for the confusion.

Regards.

No problem.  I’ve reached out to DJI to see what they make of it.  They’ve requested the same three image files which I’ve sent them. I’m curious what they’ll have to say.  I"ll definitely be updating this as i get more info.

Is there any update on this issue? I am seeing the exact same issue.

I have a ticket open with DJI…where i’ve informed this all about what information I’ve acquired through this forum.  No telling where that will go or how long it will take to get there.  You say you’re having the “exact” same issue…assuming it’s with the MAVIC 2 and PIX4D my only workaround has been to clear the Geolocation and orientation data by pressing the clear button and processing the images as usual.  The result so far has been a more accurate image (i.e. without the blur issue)  however the resulting image is A. not geolocated AT ALL and B. way off scale and has to be scaled manually via accurate measurement landmarks visible in the resulting image.

 

I have removed the Geolocation and orientation data, but I am experiencing a misalignment when processing Mavic 2 Pro. When I keep the Geolocation data, the roadway becomes curved in a Z-direction and causing misalignment in the orthomosaic and pointcloud. 

For what its worth, there is (IMO), a significant sensor issue with the hasselblad equipped airframes as well.

I suspect Pix4D has accounted for this in their sensor characterisation techniques. 

So the semi good news is that apparently Pix4D mobile app has a new update regarding support for the Mavic 2.  Hoping this will fix the problem with images taken vis the PIX4D mobile app.  There doesn’t seem to be an update for the Pix4D desktop app though and unless there is I’m hard pressed to imagine if PIX4d will be able to properly process images from the DJI app.  

I will try clearing the geolocation next time I process images. In the below image the blue circle is my flight area and the red circle is where its coming in at in pix4d. Its off to the east about 5,100 feet, luckily I didn’t need the orthomosaic for this project. I was able to process building elevations and get a working point cloud and mesh using images from the mavic 2 pro.

 

I will try out the updated mobile app next flight, but I agree with Jack I do not see that resolving this issue without a desktop app update.

 

Yep…same issue I have…I’m curious…can you process it for the ortho two times…one with geolocation-and-orientation on and one with it off and compare the two orthos. 

My results are it comes out with a “cleaner” ortho with it off.

Actually, we also get good results by zeroing out the Altitude values.  Pix4d still places the image in the wrong location but it comes out very clean.