Litchi Mission Planning: what spacing / altitude / speed / imaging frequency should I use for a 10 acre orthophoto?

[eddiearni]

Hi, I'm flying a Phantom 3 Professional and using Litchi for mission planning and flying. Intending to try out WebODM for processing.

I am flying the 10 acre farm where I work, making an orthophoto for mapping purposes. On a shoestring budget.

Never done this before though I have experience with GIS and UAS flying / photography.

My Question:

What is ideal:

spacing (how far apart should each pass over the land be? At present I have it set for 15m )

altitude (I'm thinking 100m AGL)

speed (I have no idea but I assume slower is better, thinking maybe 20km/h)

and frequency (I'm thinking a photo every two seconds)

Any advice appreciated, thanks!!

 

[MapMaker53]

I would say there are too many factors to guess at this. Do you know what resolution you want your final image to have? Your altitude will determine your resolution and number of images needed for your coverage. Do you know how much image overlap you will need? My recommendation would be to use the free "Drone Pilot" app (by Maps Made Easy) to set it up and produce the images for you because it automatically calculates everything for you based on the altitude you wish to fly. Once you set up and fly a mission, you can then have them process the images for a fee, or use whatever service you originally intended to use. Using Map Pilot will make the process so much easier for you. And their processing fee is quite reasonable. I've used Map Pilot many times. Here is an example of one I recently flew to map the extent of invasive water lilies along a lake shoreline.

Like Litchi's waypoint missions, you can pre-plan your mission and call it up in the field and make any last minute adjustments to it. I originally intended to launch where that purple dot is, but changed that to a different location the morning of the flight. It's easy to set up and allows you to rotate the flight pattern to any angle you desire with two fingers. You can also fly a grid pattern for greater accuracy when creating 3D models. Again, downloading the software and flying your mission is free.

 

[eddiearni]

Thanks for the tip, Map Pilot looks like just the thing for me!

Precision for this project only has to be less than 1m, the end product being a more or less accurate georeferenced map.

Image overlap, I have no idea, am presently searching the internet for this kind of information.

Any additional advice / info appreciated, thanks again!

 

[MapMaker53]

Map Pilot will set up the recommended overlap when you set up a mission. Typically I don't think they recommend less than a 75% overlap. Yes, I was a little surprised at that too, but apparently that is needed to compensate for any lens distortion. But you are free to adjust any of the parameters you wish when setting up the mission. I generally go with what is recommended once I decide on what altitude I want to fly (which again affects the number of photos, distance between flight lines, number of batteries needed, and resolution). If you need a second or third battery for a mission, Map Pilot will bring the Phantom back for a battery swap and then continue the mission where it left off. I have yet to use that feature.

 

[jjdun770]

Image overlap, I have no idea, am presently searching the internet for this kind of information.

Any additional advice / info appreciated, thanks again!

75-80% overlap on the front and sides should work just fine for what you’re wanting to do.

 

[eddiearni]

I would use Map Pilot but apparently it is only available for iOS, all my devices are Android. Thinking I'll go with Litchi, flying 30 km/h at 100m in a cross hatch pattern with each cell 15m x 35m, an image taken every 2 seconds for 15 minutes of flight.

(There's gotta be somewhere I can enter those figures & get an estimate of overlap...)

Then process the imagery using "Maps Made Easy", seems like a safe bet.

 

[jjdun777]

I would use Map Pilot but apparently it is only available for iOS, all my devices are Android.

You can use litchi altho that's really not what it's made for or since you're on Android I'd suggest either 'Drone Deploy' (free 30 day trial) or my new favorite 'Measure Ground Control' (2 free maps per month). They are both flight apps that you setup beforehand in the app with the settings you'd like and then they fly the mission autonomously. Being 10 acres it may require more than one battery in which case they will both pause, come back to the home point so you can swap it out and then resume where it left off. They are both cloud based options so if you wanted you could upload the photos when you're done and they'll make the orthomosaic for you or you can take the pics and upload them to MME if that's your preference. MGC is fairly new but I gotta say I really like their app and cloud based processing platform (their processing is based on the Pix4d platform) but they are much more affordable lol. They also have LAANC authorization from their flight app which is nice but honestly it's a matter of opinion so you can try em both and see what you think. Just wanted to take a minute to put my 2¢ in to hopefully save you the headache from trying to use Litchi for mapping. Hope this helped.....

Jody

 

[Meta4]

What is ideal:

Definitely not making a guess about shooting at intervals with Litchi.
A real mapping app is necessary.
DroneDeploy is another good one to look at.

 

[Earls Court]

I agree with all the suggestion. I use Map Pilot because is is free, easy to use and take the guesswork out of the equation, it is a pity only available on IOS. Drone Deploy is a good (maybe better option based on reviews) but you have to register and fly your mission within the 30 day trial period to get it all for free. Flew my first two missions successfully with Map Pilot at 70m hight and 75% overlap.

 

[Meta4]

Drone Deploy is a good (maybe better option based on reviews) but you have to register and fly your mission within the 30 day trial period to get it all for free.

DroneDeploy (and probably all the other mapping apps) are free for planning, flying and acquiring images.
You only pay if you upload your images to them for their processing.

 

[Martin Healy]

Hi, I agree with others who have steered you towards Drone Deploy. Read through their guidance info to get the best out of the DD app. WebODM does a good job on the orthos I tried last year.
Since you have Litchi I would also suggest that you try HiveMapper which uses a different approach - you record a video of the 'lawn mower' flight pattern and they process it for free. Read all their guidance and download their lawn mower flight plan. This method means that you also have a video record of the farm at a point in time for future reference. If you repeat the same HiveMapper mission at intervals then HiveMapper has a neat trick of highlighting changes that have occurred on the ground between the flight dates.

All the best, Martin

 

[Foxtrot75]

You could use Drone deploy, they do a 14 day trial and will process the map also. As with the other reply over lap will be calculated for you but usually 80%

 

[GrantD]

I use Litchi and Webodm - generally successfully. I fly at 100m giving 5cm per pixel with a Phantom 4 V2. I fly on lines 40m apart with photos taken every 20m facing along the line travelling at 20km/h. This gives about 80% overlap. I do the initial planning of lines in QGIS before sending endpoints of lines as a kml to Litchi to finish the flight plan. Litchi is very good for this. But even with a Core I7, 512gb SSD and 32gb RAM I run into problems if I attempt to process too many photos with Webodm - it seizes up. I think the recommended minimum for Webodm is 16gb. But with this computer processing your 10 acre job should be easy - and flying it would be only one flight using about half a battery.

 

[Harleydude]

Professional mapper here...

Regardless of what you're heard so far...

Because your plot of land is so small and essentially flat with little contrast (which may cause errors), better to over-collect than to have to go back. Do the following:

* 75/75 overlap
* 250' AGL (do terrain aware if possible).
* Shutter priority 1/1600 to 1/2500 (faster shutter produces sharper image)
* Double grid
* Set speed to max (your software will slow down the drone to a safe speed)
* If your drone has a mechanic shutter setting, use it
* Fly 2 missions:
--------- first mission nadir (which will probably be about 10 minutes if that)
--------- second mission oblique 15°

This will absolutely guarantee the best data for rendering in Pix4D or other mapping software.

D

 

[ADobrovolskiy]

I do the initial planning of lines in QGIS before sending endpoints of lines as a kml to Litchi to finish the flight plan.

I'm curious why you don't use flight planning software with photogrammetry missions planning tools?
There are a lot of such software, from free DJI GS Pro and till UgCS (I'm CTO of SPH Engineering - developer of UgCS)