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I am relatively new to GIS.

I am studying wildlife (I have collar data that lasts a year) and my supervisor and I would like to create an annual NDVI map for my projected area. I was able to download a years with of imagery (although some does have cloud coverage) ranging from the year that I am working with.

Now, from what I understand - with one Landsat image (lets say representing a day out of a specific month). I choose Bands 2, 3, 4, and 5. I then use image analysis (in Arcgis) to composite those bands and calculate NDVI from there.

  • However, I would I do this with multiple landsat images that span across a year?
  • do I composite the bands and calculate the NDVI separately one by one and then merge the separate NDVI rasters?
  • Or do I simply choose bands 2, 3, 4, and 5 for all of the separate landsat images (so for example, bands 2-5 for april, 2-5 for may, etc) and then make one composite (representing all of the months) from there?

I tried looking for tutorials on how to composite and annual NDVI but to no avail.

I calculated my individual monthly NDVIs (had some cloud coverage but not directly on the mountain that I am working with). Every individual NDVI had values between -1 and 1 (looking good so far). Read into cell statistics and decided to take all of these separate NDVIs and plug them in with the overlay being the mean.

Results: http://i.imgur.com/RXVS23Z.jpg (high being red and low being green). Also, results with a separate raster (of the forests found in the mountains) overlaid and put on transparency for comparison. http://i.imgur.com/aYRqSoc.jpg The only thing that I am concerned about is how my values (from the cell statistics output) range from 0.53317 to - 0.232147 and not between 1 and -1

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    Can you really summarise NDVI in this way? Surely you just have measures of NDVI for particular points in time (particular images). You could make summary statistics over a year, or interpolate between temporal observations, but it's not exactly NDVI per se. – alphabetasoup Apr 16 '16 at 22:46
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    What is your ultimate objective? – Aaron Apr 17 '16 at 2:04
  • I apologise, My ultimate objective is to have an overall idea of 'greenery' surrounding my study site. Since the animals have collared data lasting a year and their behaviour isn't really dictated by seasonality, I simply would like to try to map out vegetation areas from a years worth of Landsat data. So, I am not sure what the technical term would be..annual NDVI? – Redskies421 Apr 17 '16 at 9:38
  • I think for this you'll have to consult with literature on topic you're working on. Then you'll have a better idea if you'll have to do some sort of regression analysis or something similar. I doubt ArcGIS will do what you want it to. ENVI has pretty much everything you'd need for this. – Goldring Apr 17 '16 at 19:16
  • thank you so much for your response, can you explain why ENVI has everything that I need for this? I also have been looking through the bio lit and the authors have only stated 'we used NDVI' unfortunately, I am quite novel when it comes to GIS. – Redskies421 Apr 17 '16 at 22:05