Understanding image overlap on large area missions + large area mission planning

Hello all, hope you can help me with some questions I have.

I fly a Phantom 4 PRO and use MapsMadeEasy + Pix4D.

So - I have a mission to fly in the coming week, about 2.5 km long and 100 - 150 meter wide. I have tried to fly the mission before but I fail to make a good map/model. I am not able to stand at one point and fly the entire mission from that spot because of the terrain and length, I will loose contact with the drone.

So in white line in the image below you can see the approximate flight path I need to make. The height difference is about 50 meter in the area.

Last time I divided the mission into 4 submissions to keep the drone in a safe distance from me. I did use MapsmadeEasy because I could use the terrain modell + the import of KML file to plan my missions (flight height realitive to the terrain). The only problem I have with MME is the flight speed/motion blur and the difficulty to easy turn the speed down without activating the “fly accordning to light conditions” - but this will make my one day mission to a week…

So the first question I have is related to the submission overlap. I did as I said plan the mission as 4 submissions. The problem is now when I try to process the data as one (1) mission (incl all 4 submissions) it will not generate a modell. I think (I might be wrong) I have planned the submissions with to much of a overlap. Now I mean overlap between submissions. I overlaped submission 1 with submission 2 by 100-150 meter. Making the “join” between submissions alot more “image intense”. Did the same between submission 2 and 3 and so on. I think this messes up the entire modell because stiching problem (I could be wrong off-course).

I am able to process the submissions separately.

SO - when planning a mission like this were you need to be in safe distance to the drone, how do you plan/“join” multiple missions. Can you overlap the missions and then process them as one (can it be a webodm process adjusment that I failed to do in my last attempt?). Do the submissions need to be in direct connection to each other with no overlap - what would be the best method for this?

Please give me some tips how I can make a better map over the area. :smile:

Thank you in advance.

The submissions need to overlap if you want to process them as one (and yes you can process all images at once even if they are captured from different missions). As far as overlap between submissions, they don’t need a lot of overlap, just enough so that there are common overlap images along the borders. If you want a precise measure you could compute the area footprint and attempt to have ~30-50% overlap between the edges of each submission, but that’s probably overkill. Just make each submission overlap a bit https://gis.stackexchange.com/questions/75405/aerial-photograph-footprint-size-calculation

More importantly, for large areas, make sure you follow best practices to maximize angle and height variation for better self-calibration. https://www.opendronemap.org/2019/09/self-calibration-of-cameras-from-drone-flights/

Agreed with Piero on all the above. Current best recommendations are here: https://smathermather.com/2019/12/16/optimizing-flight-planning-for-calibration/

After I get back from holiday, I’ll get those posted to the OpenDroneMap blog and docs, but not before. :slight_smile:

Thank you for your feedback.

As I explained I did fly this mission before and divided it into 4 submissions. I was able to run all the submissions seperatly but not as one (1) task.

I did put up the submissions on a AGOL webapp. Here you can see the overlap I have on each mission. Submission 1 (in the webapp) is actually 2 missions. I did run them all as Fast orthophoto. Would you say that this may be a problem if you look at the outcome - I mean to run them as one task?

One thing I noticed is the difference in xy position between submission, about 10 meter between 1 and 2 and a little less between 2 and 3. Normal? Also there is a big distortion on submission 1 just in the tree section - I have marked it with a polygon.

http://structormiljotek.maps.arcgis.com/apps/View/index.html?appid=f99db039902740b88a59a9847d6730f2

I am at the moment limited by the PRO version of WebODM Lightning (1500 images/map). And the mission is in total around 2300. But my node-odm-1 (manual) keeps on failng so I am trying to understand why.

WEBODM_waiting

I am going out to fly the mission again to get some new images. But I would like to understand why the mission keep failing in the process so maybe I can make some better flight planning before I go out again.

Again…thanks.