topic how do I extract vegetation polygons from ndvi data? in Data Management Questions

how do I extract vegetation polygons from ndvi data?

ErichList — Thu, 20 Apr 2017 23:14:08 GMT

A long time ago I used a tutorial for the community basemap to create vegetation polygons from lasdsat ir data. I'm trying to repeat the process but the old tutorial links no longer work. Is there a wy to access this info still? The old link was help.arcgis.com/en/communitybasemap/10.0/help/index.html#/Vegetation/01010000000m000000/

I've seen this article How to Create NDVI Maps in ArcGIS - GIS Geography but was unable to download imagery from the usgs that had nir band. I also found the ndvi data on arcgis online but cant figure out how to get the bands to just display 1 or -1 which I think is step then turn in to a grid then polygon... does anyone else remember this process?

Re: how do I extract vegitation polygons from ndvi data?

JayantaPoddar — Fri, 21 Apr 2017 09:06:37 GMT

You could download Landsat 8 data from USGS EarthExplorer.

The data will be downloaded as following bands.

Bands	Wavelength (micrometers)	Resolution (meters)
Band 1 - Ultra Blue (coastal/aerosol)	0.43 - 0.45	30
Band 2 - Blue	0.45 - 0.51	30
Band 3 - Green	0.53 - 0.59	30
Band 4 - Red	0.64 - 0.67	30
Band 5 - Near Infrared (NIR)	0.85 - 0.88	30
Band 6 - Shortwave Infrared (SWIR) 1	1.57 - 1.65	30
Band 7 - Shortwave Infrared (SWIR) 2	2.11 - 2.29	30
Band 8 - Panchromatic	0.50 - 0.68	15
Band 9 - Cirrus	1.36 - 1.38	30
Band 10 - Thermal Infrared (TIRS) 1	10.60 - 11.19	100 * (30)
Band 11 - Thermal Infrared (TIRS) 2	11.50 - 12.51	100 * (30)

Use Band5 and Band4 in your equation to calculate NDVI.

If required, you could also combine multiple bands to form a single raster dataset using Composite Bands (Before executing NDVI). Just ensure that the bands are in correct order.

You could also use Raster Calculator to calculate NDVI. Then you could symbolize the NDVI raster with appropriate range of values from Layer Properties > Symbology tab.

NDVI function

This index outputs values between -1.0 and 1.0, mostly representing greenness, where any negative values are mainly generated from clouds, water, and snow, and values near zero are mainly generated from rock and bare soil. Very low values (0.1 and below) of NDVI correspond to barren areas of rock, sand, or snow. Moderate values (0.2 to 0.3) represent shrub and grassland, while high values (0.6 to 0.8) indicate temperate and tropical rainforests.

Re: how do I extract vegetation polygons from ndvi data?

curtvprice — Fri, 21 Apr 2017 23:35:38 GMT

If the end goal is to create polygons (that was the title or your post, right?) and you have a Spatial Analyst license, you can use the Reclassify tool on your NDVI data to map all values you consider vegetation to 1 and all other cells to NoData. Then run Raster To Polygon to create polygons from the Reclassify results.

Re: how do I extract vegetation polygons from ndvi data?

ErichList — Tue, 25 Apr 2017 23:34:50 GMT

I needed something with better resolution so I found 1m data NAIP 2016 4Band.lyr at

https://www.wildlife.ca.gov/Data/GIS/Map-Services and used the helpful hints above to set the ir band and run the nvdi tool, export the image, run spatial analyst reclassify tool to mark the values I wanted to display for vegetation (.19 - 7) and then used the raster to polygon tool to complete the process. One thing I did notice is that because of recent drought in California, dead vegetation does not register in the nvdi data. Thanks for your help!

Re: how do I extract vegetation polygons from ndvi data?

DeanPodolsky — Fri, 14 Dec 2018 17:09:30 GMT

I realize that this is an old thread but I was wondering if you could show an image of what you end result was. I think this may pertain to something that I'm working on and I'd like to get more information regarding your original question. Thanks!