Using UAVs and NIR photography in conservation land cover classification

I've recently finished a research project using UAVs to classify land cover types on British upland heath. I'm using an APM controlled hexacopter (H550) carrying a Canon Powershot S95 modified for NIR photography. I've successfully surveyed and classified around 15 hectares in 10 minutes. Using image analysis software I've been able to classify the major land cover types with about 90% accuracy which is comparable to that obtained from imagery captured from much larger platforms using many more spectral bands.

An NDVI colour index of the orthomosaic was created and used in the classification process. This really helps in the spectral differentiation process. I think the results here show massive potential for the frequent, low-cost monitoring of the status of, and temporal changes in (sorry for the academic speak) many habitats, not just heathland.

The images below show the various outputs.

1. The full NIR orthomosaic

2. The NDVI colour index

3. The colour index overlaid on the green channel of the orthomosaic highlighting healthy and dead vegetation

4. The classified land cover types in the GIS software (Purple is Calluna dominated heath, light green is rank grass cover, brown is cut heath and green are trees)

I used ImageJ to create the NDVI colour index image, unfortunately it doesn't keep the GeoTIFF data in the output so I've used GDAL to georeference the colour index TIFF

Views: 2184


Moderator
Comment by Gary Mortimer on March 19, 2015 at 9:19am

Nice


Distributor
Comment by Guto Santaella on March 19, 2015 at 9:47am

Very well done Mark!
Did you see the session "how to geotag" your pictures using the Mission Planner?

(I helped to write the first version of this tutorial)

If you have the flight log is possible to do it when you want... (pos- processed)

Congrats!

http://plane.ardupilot.com/wiki/common-geotagging-images-with-missi...

Comment by Mark Williams on March 19, 2015 at 9:52am

Thanks Guto. I used MissionPlanner to geotag the photos from the camera. I just geotagged the photos individually. When you say it's possible to tag the post-processed images, do you mean that I could tag an the final orthomosaic?


Distributor
Comment by Guto Santaella on March 19, 2015 at 9:58am

Hi Mark,I mean to geotag all images at same time using the flight log, I think did you do it as well..

Hey, I found it on main DIY Drones page: http://swiftradioplanes.com/swifttag/

That's new for me...

;-)

Comment by Mark Williams on March 19, 2015 at 11:58am

Thanks Guto, I'll give that a go. I commited a couple of fixes for the geotagging a while ago. It is getting better.

Comment by János Mészáros on March 20, 2015 at 2:02am

Hi Mark,

Very nice work and good example of using UAVs for land cover analysis.

IMHO, I would use open-source GIS software to do NDVI calculation instead of ImageJ functions because GIS algorithms keep the coordinate reference system (or projection) informations for a rester layer. For instance, there is a Raster calculator in QGIS to perform band combinations or calculations, or way more better to use Orfeo Toolbox algorithms. By the way, latter also exists in dekstop version, called Montevideo.

https://www.orfeo-toolbox.org/

Comment by Mark Williams on March 20, 2015 at 3:23am
Thanks Janos, I'll bear that in mind for next time.
Comment by Mark Williams on March 20, 2015 at 6:16am

 thanks for the feedback Koen. I did play with the use of haralick textures in the classification process and it made a big improvement. The problem was with the processing time and power available to me, haralick computation is pretty intensive. I'd love to spend more time on it, there are a huge number of possibilities here. Mac Arthur (2008) had some good results in life stage classification of heather with object based image analysis.

Sadly my research time is very limited from now :( I'm no longer a student from June and real life beckons. I'm searching for employment opportunities in this field but they're thin on the ground. I have some ideas for enterprise but we'll see what happens there.

I accidentally deleted your post editing my response on my phone too. :(


Moderator
Comment by Gary Mortimer on March 20, 2015 at 6:38am

I think you are in the UK Mark, if you do not already have a formal piloting qualification take yourself off to Resource and get an RPQ-S that will make finding work much easier!

Comment by Mark Williams on March 20, 2015 at 12:32pm

I am indeed Gary, I'll take a closer look at Resource.

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