Mavic Air/Pro for georeferenced aerial images?

[Symeboy]

Hi folks,

I'm looking to invest in a drone to undertake aerial surveying and I'd love to hear any advice you might have.

I'm thinking along the lines of pre-programming the drone to fly to a set GPS points at set elevations above the ground, and taking still images at each point, then stitching the resulting aerial images and georeferencing them for further work in GIS.

Anyway, I think it's possible to georeference the pictures provided I have accurate data for GPS, elevation and orientation North and angled straight down.

Does either the Pro or Air record these data accurately enough?
Can you force the drone to face a specific orientation and camera gimbal direction accurately too?

The drone would also have to be able to get nice crisp stills in a stiff breeze (I wouldnt be taking it out in high winds really). Would these smaller drones have the stability required to avoid blurring?

Lastly, the software, I understand that the only way to program set routes is via some kind of app like Litchi?

Thanks!

 

[Keule]

I think it's possible to georeference the pictures provided I have accurate data for GPS, elevation and orientation North and angled straight down.

Yes, it's possible

Does either the Pro or Air record these data accurately enough?

What accuracy do you expect? Is it in the cm range or in roughly meters?

Can you force the drone to face a specific orientation and camera gimbal direction accurately too?

It depends on what app you are using to perform the mission, but generally speaking - yes.

Would these smaller drones have the stability required to avoid blurring?

It depends on what altitude you are flying, is there wind, are there gusts and a few more aspects.
What are you going to do with the images? Are you processing them by your own, or are you using one of the image processing features of the mapping app suppliers? (see below)

Lastly, the software, I understand that the only way to program set routes is via some kind of app like Litchi?

Yes you are right - Have a look at MapsMadeEasy, Pix4d, DroneDeploy, PrecisionMapper or UgGS.

 

[bushie]

Yes, it's possible


What accuracy do you expect? Is it in the cm range or in roughly meters?


It depends on what app you are using to perform the mission, but generally speaking - yes.


It depends on what altitude you are flying, is there wind, are there gusts and a few more aspects.
What are you going to do with the images? Are you processing them by your own, or are you using one of the image processing features of the mapping app suppliers? (see below)


Yes you are right - Have a look at MapsMadeEasy, Pix4d, DroneDeploy, PrecisionMapper or UgGS.

Add Drone Harmony to that list. You can pre pland a mission to photograph a defi ed area. You can preset the ammount of overlap. If itt is a large area you can get it to continue where it left of after a battery change.

 

[Lake_Flyer]

The Air doesn't have waypoint support yet. The Pro does an OK job for mapping.
DJI Groundstation Pro (IOS only) does a good job in mapping, allows to save missions, really straightforward to use, free, 100% DJI supported of course. You can easily upload the images to MapsMadeEasy for stitching, great service, free for smaller jobs.

Always try to set the height 4-5 times higher, than the highest object in the area, to get the best stitching results. Generally 50 m is OK in most cases. Fly when the shadows are short (shortly after noon). Indeed, wind is a factor. The less the better.

 

[Symeboy]

Sorry for the delay. Thanks very much for the input guys, much appreciated! I'm gonna get the Mavic Air and test that a bit, I may well invest in bigger model if I need to.

Yes, for the record I was going to use the exif data and write a little program to georeference the images, crop them, then stitch them. I'll give it a go anyway, seems that the GPS is good enough

 

[Lake_Flyer]

The Air doesn't support waypoints yet (as far as I know, I don't have the Air). But as a beta tester for Autopilot I noticed that the latest beta from last week does add support for the Air. So waypoints are probably in the next firmware upgrade.

 

[Symeboy]

The Air doesn't support waypoints yet (as far as I know, I don't have the Air). But as a beta tester for Autopilot I noticed that the latest beta from last week does add support for the Air. So waypoints are probably in the next firmware upgrade.

Thanks for the reply. Does the air need to support waypoints in order to allow 3rd party apps like lichi to dictate programmed flights?

 

[brantel]

Litchi and Autopilot have beta versions out right now that have waypoint support in them for the Air. Many people are reporting that they work as expected.

The problem I am finding with the Air (other than the lack of support from the mapping apps like Pix4d, DroneDeploy, Maps made easy and DJI Groundstation) is that the precision of the geo tags of the image is rounded to the nearest second of both lat and long. This leaves a ton of room for error and causes orthos to be off by a significant amount. The Mavic Pro does not have this issue.

The apps that are focused on mapping have great tools for developing the grid patterns to get the correct overlap and other critical parameters needed for good maps. So far, none of them have released a version supporting the Air.

I imagine that now that the new SDK is released, we may see better support for the Air and mapping mission planning tools however DJI needs to fix the low res geo tags!

 

[Symeboy]

The problem I am finding with the Air (other than the lack of support from the mapping apps like Pix4d, DroneDeploy, Maps made easy and DJI Groundstation, is that the precision of the geo tags of the image is rounded to the nearest second of both lat and long. This leaves a ton of room for error and causes orthos to be off by a significant amount. The Mavic Pro does not have this issue.

That's a shame, seems like a weird thing to do, you'd think the air would have simply copied the same GPS tech as the pro. That's a deal-breaker for me, thanks for letting me know

 

[Symeboy]

Just thought I'd report back for posterity...

Finally settled on the air and it works a treat for what I was planning. Turns out you can get at the exact coordinates but they are buried in the exif data, once you can access this its possible to georeference the images using some calculations. However, Ive found the best solution so far is to take numerous photos in a mosaic, stitch them (using Microsoft ICE) and georeference using ground control points in GIS software. The hardest thing is actually taking the photos in such a way that they overlap optimally, still havent worked out how to do this but early days....

Thanks for all the help folks

 

[brantel]

Just thought I'd report back for posterity...

Finally settled on the air and it works a treat for what I was planning. Turns out you can get at the exact coordinates but they are buried in the exif data, once you can access this its possible to georeference the images using some calculations. However, Ive found the best solution so far is to take numerous photos in a mosaic, stitch them (using Microsoft ICE) and georeference using ground control points in GIS software. The hardest thing is actually taking the photos in such a way that they overlap optimally, still havent worked out how to do this but early days....

Thanks for all the help folks

Litchi and Autopilot and others now support the MA. Many of those have the ability to fly automated flight plans and to set overlap settings to get the best possible results.

 

[JustinR]

I use a mavic pro with drone deploy and ground control points and get pretty good data. In the future I will upgrade to a drone that uses gps for elevation control(over barometer) to tighten that a little more. We are happy with what we are getting at this point

 

[53-63-6f-74-74]

I use a mavic pro with drone deploy and ground control points and get pretty good data. In the future I will upgrade to a drone that uses gps for elevation control(over barometer) to tighten that a little more. We are happy with what we are getting at this point

Are there still focus issues with the Mavic using Drone Deploy or have they been resolved? I have a couple of jobs planned in both Pix4d and Drone Deploy but so far have only used a P4 pro with Pix4d. I'm interested in trying the Mavic on a job for comparison. The P4 is capable of producing extremely accurate orthos and DEMs with proper ground control placement using RTK GPS.

 

[Niles]

Unless

Turns out you can get at the exact coordinates but they are buried in the exif data, once you can access this its possible to georeference the images using some calculations.

Do share how! I spent hours culling accurate coordinates from a flight (i.e., pulling it from litche's flight record). Planning is relatively easy, in hindsight. The Air is a great UAV, but at the risk of casting aspersions, DJI is knowingly making GPS exif data difficult to access.

 

[53-63-6f-74-74]

Unless


Do share how! I spent hours culling accurate coordinates from a flight (i.e., pulling it from litche's flight record). Planning is relatively easy, in hindsight. The Air is a great UAV, but at the risk of casting aspersions, DJI is knowingly making GPS exif data difficult to access.

Not too sure about the MA's, but EXIFTOOL can extract every bit of metadata available. There is also a GUI available HERE. You need to select the "All" button under the metadata tab to see everything available.

 

[arunabha42]

Are there still focus issues with the Mavic using Drone Deploy or have they been resolved? I have a couple of jobs planned in both Pix4d and Drone Deploy but so far have only used a P4 pro with Pix4d. I'm interested in trying the Mavic on a job for comparison. The P4 is capable of producing extremely accurate orthos and DEMs with proper ground control placement using RTK GPS.

I think the focus issue has been resolved now, though only on Dronedeploy. I have just done a few flights in the last week. Dronedeploy seems to have added a focus calibration step before it starts taking pictures. I tried Pix4D Capture, which turned out blurry still.

Earlier I was taking off with DJI Go to the mission altitude, focussing on the ground, then switching over to Dronedeploy and initiating the mission. This was a workaround that got it done, but one ended up wasting precious flight minutes switching apps (not to mention the entire point of automation gets lost).

I have not yet flown any mapping mission with GCPs and that is what I'm trying to figure out next.

Cheers!