Aerial Photography and Topographic Map interpretation and Geomorphic Mapping
The main parts of this lab come from Exercises
in Active Tectonics: An introduction to Earthquakes and Tectonic
Geomorphology, by Nicholas
Pinter, Exercise 3.
These are essential tools. You probably already know these things,
but this is a good review.
Mapping makes you notice what is there.
If your pencil tip is 0.5 mm in diameter, how big on the ground is
it if you are mapping on a 1:24,000 scale map? How about a 1:500,000
Show distribution of elevation in a region via contours (lines of equal
1:24,000 scale is typical for many places, but sometimes 1:200,000
or smaller is all that is possible.
Form of remote sensing and powerful tool for many geomorphic investigations
pages from the University of Texas with an introduction to remote sensing
and aerial photographic interpretation http://www.utexas.edu/depts/grg/gcraft/notes/remote/remote.html
Mapping and image interpretation
Basic Elements of Air Photo Interpretation--From U.
Texas link above.
"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:
1) objects are portrayed from an overhead (and unfamiliar) position.
2) very often, infrared wavelengths are recorded, and
3) photos are taken at scales most people are unaccustomed to
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
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
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".
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.
-- 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. "
Power controls 3D aerial photography (nice demo of stereo viewing)
Very important means of establishing landforms, their distributions and
relations to eachother, process distribution, and history.
I can't work on anything unless i map it first!
1) Even coverage: if there is a blank space, you did not look
2) Strive to provide detail. Do not generalize.
3) All lines mean something.
4) Consistent notation and symbology.
5) Quality control. Dashing, line wts, queries. Don't
be wishy washy, but if something is uncertain or approximate, indicate
6) Data/Ink ratio -> 1. Put ephasis on important things
(data) by putting relatively more ink in them--higher line weights, larger
7) Neatness counts. Get some nice tools.
Edward R. Tufte and visualizing information
out this link from my computers in geology class (http://geology.asu.edu/~glg410/Lectures/GLG410-charting.html)
Photogrammetry and digital imagery
This is the direction things are going. Points made above apply.
Look at this link for some advanced stereographic analysis by one of
the students in my research group:
Nice pages from
the University of Wisconsin with the basics of aerial photography
Lab assignment (due at the beginning of Lab, September 7)
1) Read lab
2) Do lab
3) Do supplemental exercise (extra handout)
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Last update August 30, 2000