Objective: Explore and familiarize yourself with different types of imagary used in Geology.  Use some selected images to interpret the geology and/or geomorphology of the area in the image. 

Equipment

ADDITIONAL RESOURCES

BOOKS -- These are available for your use during the week

• Remote Sensing and Image Interpretation, Lillesand & Kiefer, 1979, Wiley
• Aerial Photographs in Field Geology, Lattman & Ray, 1965, Geologic Field Techniques Series
• Exercises in Physical Geology, 8th ed., Hamblin & Howard, 1992, MacMillian.
• The GraphixLab Library has additional resources for GIS and ARC.   See BobE.

WEB SITES -- Check these out for good text and photos.

• Getting Started in Remote Sensing from the geology department at Carleton College, Northfield, Minnesota.  Covers the basics of remote sensing.  This is highly suggested reading!
• Aerial Photography and Remote Sensing   from the geography department at the University of Texas.  There is an especially good section entitled "Basic Elements of Air Photo Interpretation" which you should read.

Image Characteristics

Orientation

• vertical -- within ~2 degrees of vertical
• low angle oblique -- 2-30 degrees; Does NOT show the horizon
• high angle oblique -- > 30 degrees; DOES show the horizon

Spectral Sensitivity

The usefulness of images depends on differences in reflectance of various features.

Image Types

Aerial Photography

B & W Air Photos

Color Space Shuttle Photos

Satellite Imagery

LANSAT

SPOT

Radar Images

SCALE

The amount of detail shown in an aerial photography is dependent, among other things, on the scale of the photograph. A photographic "scale", like a map scale is an expression that states that one unit of distance on a photograph represents a specific number of units of actual ground distance. Scales may be expressed as unit equivalents, representative fractions, or ratios.

Those not working with expressions of scale on a routine basis confuse the terms "large scale" and "small scale". For example, which photography would have the "larger" scale - a 1:10,000 scale photo covering several city blocks or a 1:50,000 photo that covers an entire city? The intuitive answer is often that the photo covering the larger "area" (the entire city) is the larger scale product. This is not the case. The larger scale product is the 1:10,000 image because it shows ground features at a larger, more detailed, size.

1:240,000 vertical aerial photograph showing Chattanooga, Tennessee, May 21, 1971. This figure is a 2X reduction of an original photograph taken with f - 152.4 mm from 18,300 m flying height. (NASA photography, Courtesy Mapping Services Branch, Tennessee Valley Authority.) "Small Scale"

1:40,000 vertical aerial photograph providing coverage of area outlined in previous image, February 15, 1976. This figure is a 2X reduction of an original photograph taken with f = 152.4 mm from 3,050 m flying height. (Courtesy Mapping Services Branch, Tennessee Valley Authority.)

1:12,000 vertical aerial photograph providing coverage of area outlined in previous image, March 5, 1975. This figure is a 2X reduction of an original photograph taken with f = 152.4 mm from 915 m flying height. (Courtesy Mapping Services Branch, Tennessee Valley Authority.) "Large Scale"

Basic Elements of Air Photo Interpretation

Novice photo interpreters often encounter difficulties when presented with their first aerial photograph. Aerial photographs are different from "regular" photos in at least three important ways:

• objects are portrayed from an overhead (and unfamiliar) position.
• very often, infrared wavelengths are recorded, and
• photos are taken at scales most people are unaccustomed to seeing

These "basic elements" can aid in identifying objects on aerial photographs.

• Tone (also called Hue or Color) -- Tone refers to the relative brightness or color of elements on a photograph. It is, perhaps, the most basic of the interpretive elements because without tonal differences none of the other elements could be discerned.
• Size -- The size of objects must be considered in the context of the scale of a photograph. The scale will help you determine if an object is a stock pond or Lake Michigan.
• Shape -- refers to the general outline of objects. Regular geometric shapes are usually indicators of human presence and use. Some objects can be identified almost solely on the basis of their shapes.
  • the Pentagon Building
  • (American) football fields
  • cloverleaf highway interchanges
• Texture -- The impression of "smoothness" or "roughness" of image features is caused by the frequency of change of tone in photographs. It is produced by a set of features too small to identify individually. Grass, cement, and water generally appear "smooth", while a forest canopy may appear "rough".
• Pattern (spatial arrangement) -- The patterns formed by objects in a photo can be diagnostic. Consider the difference between (1) the random pattern formed by an unmanaged area of trees and (2) the evenly spaced rows formed by an orchard.
• Shadow -- Shadows aid interpreters in determining the height of objects in aerial photographs. However, they also obscure objects lying within them.
• Site -- refers to topographic or geographic location. This characteristic of photographs is especially important in identifying vegetation types and landforms. For example, large circular depressions in the ground are readily identified as sinkholes in central Florida, where the bedrock consists of limestone. This identification would make little sense, however, if the site were underlain by granite.
• Association -- Some objects are always found in association with other objects. The context of an object can provide insight into what it is. For instance, a nuclear power plant is not (generally) going to be found in the midst of single-family housing.

REMOTE SENSING Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation. Spectral characteristics of energy sources, atmospheric effects, and sensing systems. (Note that wavelength scale is logarithmic.) space.... Oblique aerial photographs of a portion of the University of Wisconsin-Madison campus taken June 27, 1968, 11:00 AM. Normal color aerial photograph (the Visible Spectrum) Color infrared aerial photograph. Note that the football field has artificial turf with low infrared reflectance. Panchromatic film with full spectrum. Note natural grass and artificial turf have a similar tone. Black and White infrared film with filter such that only wavelengths longer than 0.7 mm. Note the natural grass now has a very light tone and the artificial turf a very dark tone. space holder for more text... Birdfoot delta, Mississippi River and Guld of Mexico below New Orleans, January 16, 1973. 1:1,100,000. (NASA images) Imaged from Landsat Band 5 (red) Imaged from Landsat Band 7 (reflected infrared)

INSTRUCTIONS

Aerial Photographs -- You will use the Mirror Stereoscope for the first portion of the assignment.  View the 4 photos in stereo and complete the following.

1. Using the basic elements of aerial photography (tone, texture, pattern, etc.), contrast the areas covered with forest to areas covered with cropland.
2. Within the forested areas there seem to be two zones that differ in tone.  Suggest reason(s) for this difference in tone.
3. Note the curvilinear texture in the upper-center portion of 64L.  What might be the geologic cause of this texture?
4. Add strike and dip symbols to the map, and estimate amount of dip.
5. Trace-out the contacts between individual rock units over the 4 photos.
6. Add structural symbols.
7. How many ridge forming rock units are exposed in the area covered by the 4 photographs?
8. Create a general stratigraphic column for the units in the area.
9. Add color to map and column for clarity.