GEOG272-Lab4 (2)
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School
University of Maryland *
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Course
272
Subject
Geography
Date
Feb 20, 2024
Type
docx
Pages
2
Uploaded by Josephmass
Lab 4 Vegetation Indices
Lab Data
: GEOG 272 Lab 2 Data.zip
. Make sure to download, unzip and save all the
files into your own folder.
Overview
We will be using ENVI to create and analyze typical (widely used) vegetation
indices. Please complete the tasks and answer the questions written in RED.
Band Ratioing
Band ratioing is a process by which brightness values of pixels in one band are
divided by the brightness values of their corresponding pixels in another band in
order to create a new output image. These ratios may enhance or subdue certain
attributes found in the image, depending on the spectral characteristics in each of
the two bands chosen. This lab will introduce you to methods of calculating ratio bands and vegetation
indices. Open the Landsat image and calculate the Simple Ratio (NIR/Red) using
ENVI's Band Math function (Basic tools > Band Math). Enter the following
expression: "b4*1.0/b3". ENVI will ask you to select which bands you want to assign
to band 4 (NIR) and band 3 (Red). [1] Interpret and discuss the result of NIR/Red ratio. Which type of features is
extracted from the band ratioing process?
[2] Compare and briefly discuss the values computed for (a) water, (b) vegetation,
and (c) urban areas.
Scatterplots are valuable image exploration aids. Create a scatterplot under Tools,
2-D Scatterplots. Select the Red band for your x axis, and the NIR band for the y
axis. This is an interactive tool, where you can create a ROI on your scatterplot by
drawing on the scatterplot and you will see the pixels highlighted in your image
window if you right click on the scatterplot window.
[3] Create a two-dimensional scatterplot and see the correlation between the red
and NIR bands. Create three ROIs in different colors and make a screenshot of the
scatter plot and the main image window. Make a discussion about the land cover
type that each ROI represents. Use ENVI's Band Math function introduced above to try generating other vegetation
indices.
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