Photogrammetry and Remote Sensing
Image Analysis
Using
specialized, extremely high-quality photographic equipment, it is possible
capture images (shown below) from either planes or satellites that can be used
to map the earth. By overlapping these images, three-dimensional views of the
earth can be obtained. The process is known as photogrammetry which is an
area of study in surveying. In the past, instruments known as stereoplotters
were used to recreate the three-dimensional view of the object. Today much of
this work can be performed on computers using digital imagery. This method of
mapping the earth's surface is responsible for products such as road maps,
highway design maps, and topographic maps, to name a few. People who perform
this work are known as photogrammetrist. Photogrammetrist must have a strong
background in mathematics and computers.
Photogrammetry can be used to determine the three-dimensional coordinates of any
point in the image. The photogrammetrist uses this information to create base
maps in support of other engineering and civilian projects. Examples of maps
developed using photogrammetry include highway and topographic maps.
Photogrammetrist in the United States Geological Survey produce a well-known
series of maps covering the entire United States known as quadrangle (quad)
sheets. These maps are often used by sportsmen.
Aerial photo. |
View of computer screen showing coordinates of measured points. |
Another branch of image analysis involves the identification
of objects on an image. Often these images are taken using the infrared bands of
the electromagnetic spectrum from satellites. These images allow a trained
person to identify items as small as a person. These images are often used to
perform assessment of environmental factors. For instance, the spread of an
uncontrolled fire can be monitored each hour to identify the hot spots, and its
progress allowing planners to best utilize limited resources. Similarly,
monitoring of insect infestation in a forest can be easily performed from these
images. The people work in this branch of surveying are known as image analyst. Like photogrammetrist, these people also need a strong
background in mathematics and computers. Often students study both of these
areas of surveying, and are classified as image analysts.
Satellite image of the western Mediterranean over Barcelona, Spain and
southern France. |
Satellite image over Afghanistan. |
|
Image from Shuttle Radar Topography Mission of
Pasadena, CA. |
|
Series of four images created by our
baccalaureate students |
|
Orthophoto mosaic of 28 aerial photos. |
Digital elevation model (DEM) of the same area. |
|
Triangulated Irregular Network (TIN) of the same area. |
Contour map (topographic map) of the same area. |
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