Dear reader,

I am doing tests making 3d-models and orthophotos at very low altitudes for archaeological research using a Mavic Pro 2. The goal here is to get as high a resolution as possible at the lowest possible altitude, to get a very detailed 3d model and ortho of a hypothetical excavation (right now I'm testing with a small area of 5x5m on a plot of recently plowed land).

Whilst the 5m altitude does get some nice first results, I was wondering if it is possible to map on an even lower altitude (preferably around 1m)? The testing scenario is above a large flat field, so I don't need to worry about flying into anything at such low altitudes in these tests.
I also noticed that the drone starts to make a weird 'hopping' flying pattern at the 5m altitude with a camera angle of 70 degrees. It goes up and down in between photo points, which affects the flight duration (it takes longer to fly the plotted route than it initially calculated). Thusfar it doesn't seem to affect the photo's or the 3d model quality, but I was wondering what causes this behaviour and how to prevent it?

I hope that you can help me solve these issues!

With kind regards,

Remko Willemstein

Good question.. what software are you using? Have you tried the DJI GS PRO software? Doesn't work on the phone you need a iPad.  I have used this to map out location but never tried at that type of altitude.

If not you may need to manually try to fly it.  I have done this in a few situations one was inside an old train tunnel.  I had to actually try to fly a grid patter as best as I could vertically Here is an example of a result on first pass.

Gateway Posted at 5-15 09:45
Good question.. what software are you using? Have you tried the DJI GS PRO software? Doesn't work on the phone you need a iPad.  I have used this to map out location but never tried at that type of altitude.

If not you may need to manually try to fly it.  I have done this in a few situations one was inside an old train tunnel.  I had to actually try to fly a grid patter as best as I could vertically  Here is an example of a result on first pass.

Gateway, thanks for your quick response! Right now I am using GSP on an iPad, It allows for a minimum altitude of 5 meters. At this altitude the ‘hopping’ occurs, so the actual altitude of the imagery is around 6-7 meters. I have also tried pix4d mapper, but with it’s minimum altitude of 10 meters this app doesnt provide me with the level of detail I’m looking for. Do you happen to know if the GSP app works with the Maverick 2 zoom in its zoomed in state? I’ve been thinking about optical zooming to solve the problem but havent found the time to test this scenario yet. It would need to calculate the zoom level into the grid im using (smaller than with 0x zoom).
With kind regards!

Gateway Posted at 5-15 09:45
Good question.. what software are you using? Have you tried the DJI GS PRO software? Doesn't work on the phone you need a iPad.  I have used this to map out location but never tried at that type of altitude.

If not you may need to manually try to fly it.  I have done this in a few situations one was inside an old train tunnel.  I had to actually try to fly a grid patter as best as I could vertically  Here is an example of a result on first pass.

I'm brand new to using a drone but have been interested in various 3d scanning/modeling techniques for years now. That tunnel model is very impressive!! Lots of detail and very clear images...

Can I ask what process or combination of software you used to obtain the images and then create the model?

Thanks!

The train tunnel entry looks very nice! How (and if) did you take into account overlap of the photos? Or was it an educated guess? Such close to surface mapping is quite like what im looking for!

Chris, I’m using DJI’s GSP app in combination with pix4d to make models like that, but this particular example was flown manually! You need to take into account that your images need a certain overlap (I usually go for 85% horizontal and 75% vertical) and then you can let the software do (most) of the work. Pix4d is licenced software, but there are also some freeware mapping/fotogrammetry applications out there.

The starting and stopping has to do with increasing the quality of image. It is able to take images from not stopping flying, but the quality is reduced (i.e. motion blur, lower resolution, 4K vs 5472 x 3648, etc.)

In regards to the battery, DJI GSPro will send the drone to the home point for the battery to be changed over, and then will resume the mission.

See image below for how to change the starting and stopping, etc., in DJI Ground Station Pro (GS Pro or GSP)

UNsyncED Posted at 5-16 21:25
The starting and stopping has to do with increasing the quality of image. It is able to take images from not stopping flying, but the quality is reduced (i.e. motion blur, lower resolution, 4K vs 5472 x 3648, etc.)

In regards to the battery, DJI GSPro will send the drone to the home point for the battery to be changed over, and then will resume the mission.
[Image]

Yes Im purposely using the starting and stopping to get the highest picture quality possible, but the drone is also flying up and down in between points for Some reason. Im trying to figure out why it does this, because i’d rather see it flying at a stable altitude.

R. Willemstein Posted at 5-16 22:45
Yes Im purposely using the starting and stopping to get the highest picture quality possible, but the drone is also flying up and down in between points for Some reason. Im trying to figure out why it does this, because i’d rather see it flying at a stable altitude.

Have you attempted to turn off Avoidance detection?  The manual says:

"Aircraft with obstacle avoidance will have this capability enabled by default in DJI GS Pro to ensure flight safety. Check that the Sensing System is operational in the current surroundings. If it is not, disable it in the “Prepare for Flight” checklist, or the mission will not be able to start."

I hope that this fixes your issue.

UNsyncED Posted at 5-16 23:14
Have you attempted to turn off Avoidance detection?  The manual says:

"Aircraft with obstacle avoidance will have this capability enabled by default in DJI GS Pro to ensure flight safety. Check that the Sensing System is operational in the current surroundings. If it is not, disable it in the “Prepare for Flight” checklist, or the mission will not be able to start."

I will try this on my next mission and keep you posted on the issue, thanks!

R. Willemstein Posted at 5-16 23:39
I will try this on my next mission and keep you posted on the issue, thanks!

I'd love to know if you had any luck with the avoidance detection.

R. Willemstein Posted at 5-16 21:02
The train tunnel entry looks very nice! How (and if) did you take into account overlap of the photos? Or was it an educated guess? Such close to surface mapping is quite like what im looking for!

sorry for the late reply.. I really guessed.. but it wasnt that hard to really pull off

Here's another possible solution.  I couldn't find any info on their website about minimum altitude but they have a free trial - https://www.dronedeploy.com/.