Air photo Interpretation

1. Airphoto interpretation
   Three kinds of knowledge required
        - subject
        - geographic region
        - remote sensing system

   Three issues unique to image interpretation
        - perspective: overhead view
        - spectrum: beyond visible
        - scale and resolution: different appearance
 

2. Elements of image interpretation
   Shapes
        - form, configuration, outline, or height

   Size
        - relative size to other objects

   Pattern
        - arrangement of objects into distinctive and recurring forms

   Tone
        - B/W photo: different shades of gray, color for color photo
        - image tone can be affected by illumination condition and
            film processing
        - human interpreter is less sensitive to subtle change in tone

   Texture
        - frequency of tonal change, roughness
        - human interpreter is good at subtle change in texture
        - illuminating angle affects texture

   Shadow
        - reveals size and shape of objects
        - feature within shadows are difficult to discern

   Site
        - topographic, geographic positions

   Association
        - characteristic occurrence of objects relative to others

3. Image interpretation equipment
   three purposes of interpretation
        - view the photograph
        - measurement
        - transfer interpreted information to base map

4. Sources of aerial photography
    Aerial photographs are available from private sector and government agencies

    EROS Data Center
    - Sioux Falls, SD, operated by USGS,
    - Two programs related to aerail photographs:
        1. National Aerial Photography Program
        2. National High altitute Photography Program

    Two sources for NY state GIS data including DOQQs
      http://cugir.mannlib.cornell.edu/
      http://www.nysgis.state.ny.us/

5. Reading: chpt 3
 
 

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