ENVI Unsupervised Classification Workflow

Software used: ENVI 5.1

The ISODATA method for unsupervised classification starts by calculating class means evenly distributed in the data space, then iteratively clusters the remaining pixels using minimum distance techniques. Each iteration recalculates means and reclassifies pixels with respect to the new means. This process continues until the percentage of pixels that change classes during an iteration is less than the change threshold or the maximum number of iterations is reached.

  1. Start ENVI.
  2. From the Toolbox, select Classification > Classification Workflow. The File Selection panel appears.

     ISO0

  1. Click Browse. The File Selection dialog appears.

ISO01

  1. Click Open File. The Open dialog appears.
  2. Select aerial_2013, and click Open. This is a 0.5-m resolution false-color image.

ISO1

  1. Click the Input Mask tab, select the depression layer as the Mask File.

ISO2

  1. Click Next in the File Selection dialog. The Classification Type panel appears.
  2. Select No Training Data, which will guide you through the unsupervised classification workflow steps.

ISO02

  1. Click Next. The Unsupervised Classification panel appears.
  2. Enter 5 as the Requested Number of Classes to define. You do not need to change any settings on the Advanced tab, so click Next to begin classification.

ISO03

  1. When classification is complete, the classified image loads in the view and the Cleanup panel appears.The following is a sample of the unsupervised classification results from part of the image. Your results may be slightly different. Notice the amount of speckling that occurs within the residential areas:

ISO3

  1. Cleanup is an optional step, but you will use it in this exercise to determine if the classification output improves. The cleanup options are smoothing, which removes speckling, and aggregation, which removes small regions. In the Cleanup panel, keep the default settings.

ISO04

  1. Enable the Preview option. A Preview Window opens, showing you what the classification cleanup will look like with the current settings. Click on the Preview Window using the Selection tool (the arrow icon located in the main toolbar), and drag it around the image to see how areas will be affected by cleanup step.The image below shows that the classification will benefit from using the Cleanup step. You can see that much of the speckling noise has been replaced with smoother regions.

ISO4

  1. Click Next. The Export panel appears.
  2. Enable the Export Classification Image check box. Use the default output image type of ENVI, and enter a path and filename for the classification image.

ISO05

  1. Click Finish. Select and display Class 1 as the water boundary.

ISO5

Advertisements

About Qiusheng Wu

Assistant Professor of Geography at Binghamton University, State University of New York

Posted on February 24, 2015, in GIS/RS, Software, Tutorials and tagged . Bookmark the permalink. Leave a comment.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

REDD+ for the Guiana Shield

Technical Cooperation Project

LidarBlog.com

Dr. Qiusheng Wu @ SUNY Binghamton

Writing Science

How to write papers that get cited and proposals that get funded

GIS In Ecology

Providing Training, Advice And Consultation On The Use Of GIS In Ecology

metrhispanic

On cities, land, ...

GeoAcademy

Open GIS: No Bounds

Scientia Plus Conscientia

Thoughts on Science and Nature

r4hydrology

Learning hydrology with R

Karl Hennermann

GIS at the University of Manchester

GIS and Science

Applications of geospatial technology for scientific research and understanding.

GISblog.com

GIS, Mapping, Remote Sensing, Geodata, Geospatial news

Whitebox Geospatial Analysis Tools

Open-source GIS development and spatial analysis with Whitebox GAT

TopoToolbox

MATLAB-based software for topographic analysis

Anything Geospatial – AnyGeo

Dr. Qiusheng Wu @ SUNY Binghamton

GeospatialPython.com

Dr. Qiusheng Wu @ SUNY Binghamton

Another GIS Blog

Dr. Qiusheng Wu @ SUNY Binghamton

ArcPy Café

Get all your ArcGIS Python Recipes here!

Planet Python

Dr. Qiusheng Wu @ SUNY Binghamton

%d bloggers like this: