MultiSpec Lab 1 - A Brief Introduction for loading Landsat TM subscenes
{Detailed documentation on MultiSpec can be found at
http://dynamo.ecn.purdue.edu/~biehl/MultiSpec/documentation.html}
2. Choose File from the pull-down menu bar, then choose open image (Ctrl + O).
3. Set correct path to \images, choose image, click Open. Prepared images to use are in the following format with a .img extension:
subp__r__name.img
sub = subscene of TM image
p__ = Landsat path number
r__ = Lansat row number
name = image location
4. The Set Display Specification for: menu will appear.
A. Area to Display: This panel denotes the size (in pixels) of the image to open. Software defaults to entire image size. Leave this as is to view the entire image set.
B. Display: This panel selects image Type and default image Magnification
Type: This selects 1, 2, 3, or more data channels (bands).
1 = grayscale image (single band)
2 = two-color image (any two TM bands in R-G, G-B, or R-B color
combinations)
3 = three-color image in R-G-B color combination. Software assumes
TM bands 4, 3, 2 as R-G-B. Band combinations can be changed from the Channels
dialog box.
Side by side = choice of individual (or all) bands shown side
by side.
Magnification: Software defaults to appropriate size of display. Leave as is for now.
C. Enhancement:
Color bits: Can be set to 24 bit or 8 bit. Software
uses 24-bit color for TM data.
Stretch: Can be Linear or Equal Area. Equal area
will provide greatest contrast. Use default Linear for now.
Min-maxes: Choices are 2 per cent tails clipped, entire range,
or user specified. Use default 2 per cent tails clipped
for now.
Treat "0" as: Can be data or background. Leave
this one on data.
Display levels per channel: Can be 32, 254, or 256. Leave
on 256.
D. Channels:
This panel assigns false colors to individual TM bands in red, green and blue color combinations. Enter the number of the desired TM band in the corresponding color box.
5. Load new histogram check box: Do NOT enable this check box. A histogram can be computed later after the image is loaded.
6. Click OK.
7. The selected image should load in a new image window with the image
file name at the top.. Once the image has loaded, image properties can
be changed / adjusted by selecting the
Processor option from
the pull-down menu and selecting Display image... (Ctrl + D)
to bring up the Set Display Specification for: selection
box. Use the zoom in and zoom out buttons
on the pull-down menu to adjust image magnification. You can also adjust
the size of the image view window by clicking on and dragging the tab at
the lower right corner of the window.
MultiSpec - TM Band Combinations, some useful information
The following tables are provided for general reference:
TABLE 1: LANDSAT THEMATIC MAPPER (TM) SPECTRAL BANDS
|
|
|
|
|
|
|
Blue-green. Maximum penetration of water, which is useful for bathymetric mapping in shallow water. Also useful for distinguishing soil from vegetation. |
|
|
|
Green. Matches green reflectance peak of vegetation. Useful for assessing plant vigor. |
|
|
|
Red. Matches a chlorophyl absorption band that is important for discriminating vegetation types. |
|
|
|
Reflected IR. Useful for determining biomass content and for mapping shorelines. |
|
|
|
Reflected IR. Indicates moisture content of soil and vegetation. Penetrates thin clouds. Good contrast between vegetation types. |
|
|
|
Thermal IR. Nighttime images are useful for thermal mapping and for estimating soil moisture. (120 m X 120 m resolution) |
|
|
|
Reflected IR. Coincides with an absorption band caused by hydroxyl ions in minerals. Ratios of bands 5 and 7 are used to map hydrothermally altered rocks associated with mineral deposits. |
TABLE 2: USEFUL LANDSAT TM COLOR COMBINATIONS
|
|
|
|
|
Normal color image. Optimum for mapping shallow bathymetric features. |
|
|
IR color image. Provides moderate spatial resolution. All vegetation will is red in this combination. MultiSpec 3-ch. default. |
|
|
Optimum for humid regions. Provides maximum spatial resolution. |
|
|
Optimum for temperate to arid regions. Provides maximum spectral diversity. |
| * TM bands listed as Red-Green-Blue | |
| (Data from Sabins, 1997: Remote Sensing - Principles and Interpretation) |