Reflectance Characteristics And Spectral Signatures

Lab Materials

Download this: lanier.zip

Lab Content

Objective

To develop and analyze the spectral signatures of Water, Vegetation and Rocks/Soils features using ERDAS Imagine

Data

The Image that will be examined will be lanier.img, which is a LandSat Thematic Mapper (TM) image of the city of Gainesville, Georgia and the surrounding area.

Procedure

  1. Open the Landsat Thematic Mapper (TM) image lanier.img, included under the Lab Materials section, on the viewer of Erdas Imagine 2013.
  2. View the image in true and false color. Under the raster tab, select Multispectral. This is the same as changing the gun assignments on the symbology tab of the properties box in ArcMap completed in the previous lab.
_static/labs/ReflectanceCharacteristicsAndSpectralSignatures/ReflectanceCharacteristicsAndSpectralSignatures_3.png
  1. Click on the Inquire Cursor icon at the top of the screen under the Home tab. The Digital Numbers (DN/File Pixel) associated with the pixel on each of the 7 layers, on which the ‘Inquire Cursor’ is centered, will be listed in the table. The DN range from 0-255 (for an 8-bit image) and represent the reflectance of features.
_static/labs/ReflectanceCharacteristicsAndSpectralSignatures/ReflectanceCharacteristicsAndSpectralSignatures_2.png
  1. Determine three locations in each of the land cover classes. Take note of the DN values for each of the features. Also take note of the X and Y values. The X and Y value can be typed into the boxes at the top of the Inquire Cursor viewer. This can be useful if the data you collected does not make sense. To move the Inquire cursor to a different area of the image, click on the center of the two crosshairs and drag. Move the crosshair to where you want it.
  2. You should now have the band wavelengths for nine pixels. Three for each landcover class. Determine the center of the wavelength for each of the TM bands i.e. average the upper and lower wavelengths for each band.
  3. Plot a graph of Reflectance (DN) vs. center of band wavelength. (Omit Band 6 as its wavelength is about 12 µm, whereas the given reflectance graph is just up to 2.5 µm)
  4. Compare the graphs you have generated with the graph of reflectance vs. wavelength.
_static/labs/ReflectanceCharacteristicsAndSpectralSignatures/ReflectanceCurve.png
  1. Write a full lab report and in the results/analysis section compare and contrast the reflectance profiles that you have generated with ones provided to you. If you note any deviations from the reflectance curves that you would expect to see, please explain the reasons for the differences.

## Adding line of text to get commit to work. Metadata ======== | Title:Reflectance Characteristics And Spectral Signatures | CreationDate:06/20/2013 | SoftwareUsed:ArcMap | SoftwareVersion:10.1