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