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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Classification of land forms 
A most important unit of mapping in airphoto interpretation studies for 
engineering purposes is the land form. The land form may be defined as the 
repetitive expression of the topography of the earth’s surface, including relief 
and slope, that reflects the geomorphic processes involved in its development 
as well as the parent material type of which it is composed. The land form is 
important in that it is a control in the location of engineering projects. 
The concepts and terminology of land forms are adapted from geomorphic 
literature. The land form types associated with the consolidated rocks of vari 
ous origins are shown in table 1. They are arranged in columns according to 
origin as Plutonic, Volcanic, Tectonic, or Remnantal (erosional form). They 
are arranged into groups according to first order topographic forms. These 
first order forms have the following limiting conditions: 
a. mountain - single summits or linear summits greater than 1000 feet of local 
relief. 
b. hill - single summits less than 1000 feet of local relief. 
c. ridges — linear summits less than 1000 feet of local relief. 
d. plateau - constant summit levels with local relief greater than 500 feet, 
bordered by an escarpment on at least one side and contains bedding planes 
in essentially a horizontal attitude. 
e. plain - constant summit levels with local relief less than 500 feet and contains 
bedding planes in essentially a horizontal attitude. 
f. valley - linear depressed feature with a surface drainage outlet. 
g. basin - curvilinear depressed feature without a surface drainage outlet. 
The land forms associated with drift materials are tabulated in table 2. They 
are arranged according to environment of origin and first order topographic 
forms. The land forms listed need no special comment here. 
The engineer must obtain background knowledge on all of the land form 
types listed from a formal course in geomorphology or by extensive reading in 
geomorphic literature. The airphoto pattern of each of these land form types 
can be described for various climatic environments. The airphoto interpreta 
tion element for detailed development is surface form, to include all elements of 
topography, drainage plan, and erosional shape. Tone and texture elements play 
only a secondary role, usually to assist in evaluating the climatic environment. 
Classification of parent materials 
The classification of parent materials for purposes of airphoto interpretation 
in engineering studies is very important. It is probably the one item that is 
least understood, because of lack of background. Too frequently, in airphoto 
interpretation studies by engineers, parent material terms are used in lieu of 
land form terms; or more frequently, land form terms are used in place of 
parent material terms. Engineers must understand these terms and use them 
properly as they generally control design.