Viewing Images In True And False Color¶
Lab Materials¶
Download this: lanier.zip
Lab Content¶
Objective¶
Students will view multispectral images in true and false color and correlate them to the reflectance characteristics of land cover classes such as urban/rocks/soil, vegetation and water.
Data¶
lanier.img, a LandSat Thematic Mapper (TM) image of the city of Gainesville, Georgia and the surrounding area.
Procedure¶
- A Thematic Mapper image has seven bands over several wavelength ranges from Blue to Thermal Infrared. Use the figure below to make yourself familiar with these wavelength ranges and the corresponding seven TM bands.
Figure 1
- Different materials have different reflectance patterns. Use the figure below to determine what the reflectance should be for broad land cover classes such as urban/rocks/soil, vegetation and water for each Thematic Mapper band.
Figure 2
- Launch ArcGIS.
- Start a new blank map document.
- Add lanier.img to the map.
- In the Table of Contents, right click on lanier.img and select the Properties option. On the symbology tab you can access the color gun assignment options and set the image band assigned to each color gun. Since this is a TM image, it has seven layers of data corresponding to wavelength ranges given in your Figure 1.
View the image in true color using the following color gun assignments:
Image Band Color Assignment Band 1 - Blue - Layer_1 Blue Band 2 - Green - Layer_2 Green Band 3 - Red - Layer_3 Red Note your observations for the colors of the rock/soils/urban, vegetation and water land cover classes.
View the image in false color using the following color gun assignments:
Image Band Color Assignment Band 2 - Green - Layer_2 Blue Band 3 - Red - Layer_3 Green Band 4 - Near Infrared - Layer_4 Red Note down your observations and describe the usefulness of viewing an image in false color verses true color. Which features stand out the most and why? Why is the Blue band in the image not very useful for purposes of remote sensing?
Now experiment with at least three more band combinations. For each band and color gun combination note down your observations of the features in the images and explain which features stand out the most. Use the reflectance graph provided to help explain your observations.
Now view each TM band layer individually by selecting the same band for each color gun. This will image will appear in gray scale. Explain the characteristics of each image based on the reflectance graph and the wavelength range for that band.