# How to create an annual NDVI from Landsat 8 imagery [closed]

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

## closed as too broad by PolyGeo♦Apr 19 '16 at 5:01

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• 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. – Richard Law Apr 16 '16 at 22:46
• 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