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NDVI flight results

Posted by Mark Williams on November 29, 2014 at 9:15am

3689627980?profile=original

Following on from my last post on modifying the PowerShot S95 for NIR photography. I have ran a couple of test flights to collect some heathland data. The last flight produced 134 photos which were stitched with Agisoft Photoscan and then processed with the Fiji Photo monitoring plugin to produce the NDVI image shown. Original output files can be found here

Areas of green/higher chlorophyll containing vegetation can be seen on the processed photo as green and red areas.

The photos from the camera are a little blurred right now as the 2007 filter is thinner than the IR block that was removed from the camera causing some focusing issues. I have a replacement non blocking filter on order that should solve this problem.

I'm making progress, I now need how to analyse this to get some quantitative data...

Tags: heath, ndvi, nir, publiclabs, survey, vegetation
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Comments

  • Chris Fastie December 2, 2014 at 5:12am
    Mark,
    It looks like the S95 images that make up your stitched mosaic vary in focus. Was the camera on autofocus? Poor focus is a common result after converting a camera, but the new filter may not be to blame. The S95 makes it easy to adjust the final three screws holding the sensor plate, so it should be possible to get very good focus with the Rosco filter installed. A glass filter can give better results, but the big variable seems to be adjusting those screws. What new filter have you ordered?
    Chris
  • Rai December 1, 2014 at 12:36am

    Hi Mark,

    Thanks lot for the info. Indeed I have tried to use the 2007 public lab filter but don't have idea yet how to analyze the result. I am now still collecting some papers to read. Thanks lot anyway Mark.

    @ Jim, thanks for the information Jim, I will try to capture some micro-algae then.

    I will definitely report the result once I can go further. Good luck

    Best,

    R

  • Jim Pullen November 30, 2014 at 12:01pm

    3701884929?profile=originalHi Mark.

    It's an area of saltmarsh over here in the UK. It was enwalled but reverted back to marsh after the seawall breached in the 1953 North Sea storm serge and was never mended.

    Multicopter was an Iris with a 3d printed gimbal.

    Area is around 70,000 m2.

    Algae should show well. I have found green seaweed shows up very well. 

  • Mark Williams November 30, 2014 at 10:40am
    @Jim. What area of land is this covering? It looks great. Fixed wing or multicopter?
  • Mark Williams November 30, 2014 at 10:39am
    Rai. I used just one camera that captures both NIR and visible light. The public labs 2007 filter allows for this. If you are using a NIR only camera then you will need to also capture RGB from another camera at the same time. There may be benefits to doing this but it is beyond my budget at the moment. Using this to find algal blooms is a great idea. I look forward to hearing how you get on with it.
  • Rai November 30, 2014 at 6:11am

    Hi Mark (and Jim),

    Thanks lot for your information. I would like to ask you a probably stupid question, but did you bring two cameras in a drone to get the NDVI images (one is still with IR block and the other one without)? Or you simply flew the UAV twice in the same area? As far as I understand (to the very limited knowledge of mine) we need to combine the true color images and NIR images to get NDVI? is it right or I am wrong? Please correct me if I am wrong. Thank you so much and would also love to share some results later on (I plan to use it to detect the algae blooming due to the eutrophication and high effluent of N and P in the river) if I can get far with this method. Thanks lot and good luck.

    Best,

    Rai

  • Bill Isenberger November 30, 2014 at 5:21am

    Cool drone application!

  • Jim Pullen November 30, 2014 at 12:51am

    3701884712?profile=originalGreat stuff,

    I have converted a ixus 220 and have been able to produce some images. I have found that getting the white balance correct is most important.

    This image is of a salt marsh, muddy creek, sea wall plus an oil seed rape field which has just sprouted at the top of the image 

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