I am trying to become more familiar with processing NDVI values in GIS. However, despite its usefulness, it seems to have some limitations. Namely, creating NDVI values across a large scale can be problematic if shading (i.e. cloud cover) and other lighting conditions are not constant especially when comparing NDVI values of the same area over time (if I am understanding this correctly). I have local digital images of 1 meter square plots taken from a high resolution hand-held camera (and with a hand-held NDVI camera) of vegetation plots at a height of ~5 feet. I would like to generate an average NDVI value for these images and use them as covariates in a survivial model of my target species. Ideally, I would upload these photos as TIFFs into ArcMap for processing. I have seen people use the red and infra-red bands from Landsat images to generate an NDVI value for the raster layer. Could I apply this to my photos?

Also, is it acceptable to use the NDVI value at each location as an independent predictor variable? Or, will the local NDVI values be confounded by variation in lighting conditions even if I'm not comparing the values from each image directly? I standardized the area photographed, time of day (10am-2pm) photos were taken, and camera settings.

  • What do you mean by "relative" NDVI value? Also, could you go into more detail on your sensor and the vegetation plots? How large are the plots? What altitude did you acquire the imagery? – Aaron May 11 '15 at 15:27
  • Is your camera calibrated? How are you getting near-infra red (0.75-0.90 µm) from a camera? – Jeffrey Evans May 11 '15 at 15:47
  • You can certainly account for uncertainty due to NDVI variation. However, it is unlikely that the data will be "independent". Since the data represents a time-series it will undoubtedly exhibit serial autocorrelation that will need to be accounted for in your specified model. – Jeffrey Evans May 11 '15 at 17:12
  • I added information above. Pictures are taken from a hand-held NDVI camera, and a regular Nikon Coolpix camera. Both from heights of about 5 feet. Plots are 1 meter square. Photos taken between 10am and 2pm.... I apologize; but, I'm having trouble articulating my issues and desired outcomes. I'm a novice GIS/NDVI user (at best). – Matt May 25 '15 at 18:10

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