Mapping huge area

[agrofactory]

Hi everyone,

I have been asked to map a great surface around 20 km² with required GSD of 5 cm/px.

The only way I've figured out is dividing the area by four and trying to map each square of 5 km² with a different EVO II. The issue comes with the requiered GSD. I would have to fly at 220 m high. Completely impossible. With the legal limit of 120 m high, my GSD is 2.72 cm/px. The big con is that the fly would take around 6 hours at around 20 km/h (per each square). As far I know the only way to modify the GSD value is changing the fly altitude...

Maybe one of you could bring me some advice for this task? Many thanks indeed

 

[Socketcreep]

This sounds like a job for Dronedeploy. Have you looked into their software?
They don't list Autel yet as a supported drone, but considering your issue applies to any drone, maybe there's a way to convert XML data— or worst-case: saddle an Insta360?
See: https://www.dronedeploy.com/product/supported-drones

A similar conversation here on this forum (mapping a golf course)
https://autelpilots.com/threads/golf-course-mapping.9930/post-93260

 

[Pawel]

Wow, 20 km2 is quite a bit of area. A lot of flying. This is job for a fix-wing rather than rotor.
I am not advocating for anybody but I am sure any mapping software can handle the job. Not only DD.
As for flying part I am sure that Autels' pilot app on the RC can handle 2d mapping missions.

GSD of 5cm - this has advantages - shorter flight time, less pictures, shorter processing. Yet you would need to get extra permission for flying higher than 120 m. And this might be tricky, I guess.

 

[Detritalgeo]

Yes this is likely easier for a ebee, wingtra or some other mapping VTOL,..

I am not sure where you are located but is many countries you can apply for a special flight authorization to exceed the hard cieling of 120m 400'

 

[Socketcreep]

I just watched this (cough) Skydio presentation on 3D scanning, and— WHOA. They seem to be leading this market:
“Keynote - The New Era of Autonomous Inspection”

 

[agrofactory]

My final plan would be to divide the main area in four sectors (5km² each) and fly each sector with a couple of EVO's at same time. Around 3 hours of flying...per day.

 

[Pawel]

My final plan would be to divide the main area in four sectors (5km² each) and fly each sector with a couple of EVO's at same time. Around 3 hours of flying...per day.

Good luck. Have fun flying.
Pls. share how it went - flying and processing.

 

[TN Drone Services]

My final plan would be to divide the main area in four sectors (5km² each) and fly each sector with a couple of EVO's at same time. Around 3 hours of flying...per day.

Note that when you combine images from multiple days in DroneDeploy it can cause issues with your map. They prefer same day imagery IF you are going to combine all the images from multiple days into one map. One issue you can run into is elevation anomalies where it thinks one day's elevations are maybe 50 feet higher above sea level than the other day's imagery. I've experienced this first hand.

 

[mblacklin]

Hire a conventional aircraft. 20km² is a ridiculous amount for any typical UAS.

 

[Pawel]

Indeed. 20 km2 is 2000 ha! Which is a lot.
Ebee classic can do app. 200 ha in an hour, will eat 2 batteries, at 120 m ATO if one is lucky and circumstances allow. This gives 10 plus hours of flying, would guess 12-15 hours on site and number of batteries.
Any way good luck! Share how it went.

 

[agrofactory]

Hire a conventional aircraft. 20km² is a ridiculous amount for any typical UAS.

I know, so far they just want a draft of the proyect. I agree that is nonsense.

Note that when you combine images from multiple days in DroneDeploy it can cause issues with your map. They prefer same day imagery IF you are going to combine all the images from multiple days into one map. One issue you can run into is elevation anomalies where it thinks one day's elevations are maybe 50 feet higher above sea level than the other day's imagery. I've experienced this first hand.

Wow, even that can go wrong huh? And I though that my biggest issue regardind elevation was not having follow terrain function. Appreciate the tip.

 

[Detritalgeo]

Note that when you combine images from multiple days in DroneDeploy it can cause issues with your map. They prefer same day imagery IF you are going to combine all the images from multiple days into one map. One issue you can run into is elevation anomalies where it thinks one day's elevations are maybe 50 feet higher above sea level than the other day's imagery. I've experienced this first hand.

This would have to be a non RTK unit, correct?
If this is happening with an RTK drone then there may be a problem with the procedure of establishing the base station each day.
If it is a regular non-RTK unit without tight GCP's near the data seams then yes absolutely there will be shifts in the data. The consumer-grade GPS has a fairly large absolute vertical error but the reported value is fairly consistent during a flight. The GPS elevation will change quite a bit each day when the satellite constellation is different.

 

[Rusty_SWO]

Not going to comment on fixed- vs rotary-wing on this, or overall size, etc., but the altitude you fly at isn't what determines your GSD. It's what determines your optimal GSD.

When you create your ortho, you should be able to set the GSD there, and set it to whatever you want. Metashape (as an example) will default to the best possible GSD, but I can override it- I could fly at 1000m AGL and set .5mm GSD for ortho generation if I really wanted to and get about a million times more pixels than necessary. Conversely, I could fly at 10m and set 1m GSD and lose every bit of detail, though I can't imagine why I'd want to do that. Or I could let it calculate the ideal GSD and generate the ortho at that resolution, and then export it at higher or lower GSD if I want.

 

[agrofactory]

Indeed. 20 km2 is 2000 ha! Which is a lot.
Ebee classic can do app. 200 ha in an hour, will eat 2 batteries, at 120 m ATO if one is lucky and circumstances allow. This gives 10 plus hours of flying, would guess 12-15 hours on site and number of batteries.
Any way good luck! Share how it went.

Just a quick update FYI. I ended up doing the job with the DJI 3M as they require multi-spectral imagery and I needed to be able to follow the terrain as it was very steep. So I split the job into four sections and flew one a day. Almost 2TB of data. Pretty insane. Seven batteries too, of course. The drone worked perfectly 90% of the time. Sometimes it just stops the mission and sometimes the 500m altitude limit made me pick up the gear and take off from a higher point to complete the task. Anyway, I'm glad I'm not the one who has to process all those files.

 

[Pawel]

Just a quick update FYI. I ended up doing the job with the DJI 3M as they require multi-spectral imagery and I needed to be able to follow the terrain as it was very steep. So I split the job into four sections and flew one a day. Almost 2TB of data. Pretty insane. Seven batteries too, of course. The drone worked perfectly 90% of the time. Sometimes it just stops the mission and sometimes the 500m altitude limit made me pick up the gear and take off from a higher point to complete the task. Anyway, I'm glad I'm not the one who has to process all those files.

hi, thanks for this update.
What alt. did you fly at?
What GSD for RGB and multispectral did the job yield?

 

[agrofactory]

hi, thanks for this update.
What alt. did you fly at?
What GSD for RGB and multispectral did the job yield?

Around 109 meters above ground level. The required altitude for the 5cm/px GSD I needed.

 

[Pawel]

Around 109 meters above ground level. The required altitude for the 5cm/px GSD I needed.

thanks. sorry forgot to ask - what was a speed you were flying these missions?
Sounds like you did a good job.
M3M seems to be capable of doing big projects. Courious to know how processing went. Do you know what software will be used?
I would love to see final map/s.
Congrats!

 

[agrofactory]

thanks. sorry forgot to ask - what was a speed you were flying these missions?
Sounds like you did a good job.
M3M seems to be capable of doing big projects. Courious to know how processing went. Do you know what software will be used?
I would love to see final map/s.
Congrats!

If I'm not mistaken, I flew at about 9m/s. And I think they used Metashape for the processing. I'm also very curious about the process. Maybe they split the job into several clusters because they had the ortho, DMS and the point cloud in a day or two. Unfortunately, I can't share it because I'm not the owner of the images. If they decide to make the job public, I'll let you know.

 

[Pawel]

If I'm not mistaken, I flew at about 9m/s. And I think they used Metashape for the processing. I'm also very curious about the process. Maybe they split the job into several clusters because they had the ortho, DMS and the point cloud in a day or two. Unfortunately, I can't share it because I'm not the owner of the images. If they decide to make the job public, I'll let you know.

Thx.

 

[SARty]

the altitude you fly at isn't what determines your GSD...

...I could fly at 1000m AGL and set .5mm GSD for ortho generation if I really wanted to

Can you elaborate on what you're referring to here?