LAB 3

BLACK & WHITE AIR PHOTO

IDENTIFICATIONS & INTERPRETATIONS

(revised 06/01)

 

    Photo interpretation often involves a considerable amount of subjective judgment, consequently it is often referred to as a combination of art and an exact science.  Actually, it is both.  You have now mastered (hopefully) some of the photogrammetric tools available to the image analyst, yet these skills must often be supplemented with deductive reasoning to supply a logical answer to the perennial question, "What's going on here?"  The interpreter who knows which features to expect in a given locality, as well as those not likely to occur, can make a positive identification in a shorter period of time.  The value of experience and imagination can hardly be overemphasized as well.

 

     A vertical or near-vertical view of a feature from an altitude of several thousand meters can be quite confusing.  An experienced image analyst exercises mental acuity as well as visual perception and consciously or unconsciously must evaluate several factors in identifying features on imagery.  Prominent among these are:

 

     Shape.  This characteristic alone may serve to identify some objects.  Examples include a highway "cloverleaf" intersection, an airfield, or a football stadium.

 

     Size.  Both relative and absolute sizes are important.  Thus a superhighway will not be confused with a rural road, or a small residence with an apartment building.  Size, of course, is a function of the image scale.

 

    Image Tone.  Objects of different color have different qualities of light reflectance and, therefore, register in varying shades or tones on an image.  Examples include light versus dark topsoil, cultivated versus fallow fields, or coniferous versus broad-leaved tree crowns.

 

     Pattern.  If the spatial arrangement of trees in an orchard is compared with that of natural vegetation, a contrast in patterns will be evident.

 

     Shadow.  A truly vertical photograph of a tall smokestack or an isolated oil derrick might present a difficult identification problem, except for the characteristic shadows cast by these objects.  By the same token, shadows may also be offensive to the interpreter because they obscure ground detail.

 

     Topographic Location.  Relative elevation, including drainage features, can be an important clue in predicting soil conditions or the probability of encountering a particular vegetative association.

 

     Texture.  The degree of coarseness or smoothness exhibited by images can be useful key to identification.  Texture, just like object size, is directly correlated with image scale.

 

MATERIALS NEEDED:  magnifier, ruler, calculator, topo sheets

 

 

PART I - BLACK AND WHITE PHOTO IDENTIFICATION

 

1A       PHOTO: 3104 CITY OF AUBURN 2-28

 

            A.  Identify _______________________

 

            B.  Identify _______________________

 

            C.  Identify _______________________

 

            D.  Identify _______________________

 

            E.  Identify _______________________

 

            F.  Identify _______________________

 

1B        PHOTO: 3104 CITY OF AUBURN 1-5

 

A.     Identify _______________________

 

B.     Identify _______________________

 

C.     Identify _______________________

 

 

           

2.         PHOTO:  NY-9-1489-976     

           

J.       Identify_______________________

 

            K.  Identify _______________________

 

            L.  Identify _______________________

 

            M.  Identify _______________________

 

 

3.                  PHOTO:  FL-2CC-67

 

            N.  Identify _______________________

 

            O.  Identify _______________________

 

 

 

 

4.                  PHOTO:  3104 CITY OF AUBURN 1-8

 

A.                 Identify____________________

 

B.                 Identify____________________

 

 

5.                  PHOTO:  5-56

 

R.  Identify _______________________

 

            S.  Identify _______________________

 

            T.  What accounts for the difference in tone 

                on the bridge? _________________

 

            U.  Identify _______________________

 

 

 

Albany, New York

 

Photos 1A and 1B are examples of standard metric photography which are currently used by many government agencies.  As with most aerial photos of this type, they are taken with an overlap of about 60% for stereo viewing and utilize panchromatic film with a yellow filter for more effective haze penetration.

 

Locate the approximate areas of coverage in the two photos and orient the north direction (see recommended map list).

 

1.  Find the petroleum storage tanks on Photo 1A and describe the significance of their location.

 

2.  Study the bridges crossing the Hudson River.  Which ones are railroad bridges?  What evidence can be used to determine this?

 

3.  From the bridges, what can be said about the navigability of the river?  State the supportive evidence.

 

4.  Identify the Central Business District (CBD) in Photo 1A.  What evidence supports your determination?

 

5.  How do the street and housing patterns reflect the various stages of settlement, subsequent developments and expansions of the city?

 

6.  Describe some features that would be useful in determining the housing quality of a neighborhood from aerial photos.

 

7.  What evidence of construction or urban renewal is visible in the downtown area?

 

8.  How is the bridge under construction related to the downtown area construction?

 

9.  The northwest end of the large white semicircular area near F-15/16 to the northwest end of the large dark rectangular area with a light toned rim in Y-7 is two miles on the Albany 1:24,000 topo sheet.  Determine the scale of this photo.  Discuss the sources of possible error from this determination.

 

10.  What is the actual width of the Hudson River at the highway bridge crossing?