About Air Photos
What is an aerial photograph?
An aerial photograph is a photographic image of a portion of the earth's surface taken with a camera mounted in a fixed-wing
aircraft.
How much area does an aerial photograph cover?
The amount of area covered by a photograph depends on its scale, as the size of the photograph is constant. Individual photographs
cover relatively small areas, ranging from 1.6 km x 1.6 km (1 mi. x 1 mi.) for very large scale photography (1:5 000), to
15 km x 15 km (9 mi. x 9 mi.) for small scale photography (1:60 000).
What is photograph scale?
The scale of a photograph, like that of a map, is the ratio of distance on the phot ograph to the corresponding distance
on the ground.
So, for example, if the scale of a photograph is 1:30 000, this simply means that one unit of any measure (inches, cm, etc.)
represents 30,000 units of the same measure on the ground.
All areas of the province are available at either medium or small scales, while large-scale photographs are available for
limited areas.
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Scale
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Metric (1cm =)
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Imperial (1 inch = approx.)
|
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1:15 000
|
0.15 km
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approximately 1/4 mi.
|
|
1:20 000
|
0.20 km
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approximately 1/3 mi.
|
|
1:30 000
|
0.30 km
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approximately 1/2 mi.
|
|
1:40 000
|
0.40 km
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approximately 2/3 mi.
|
|
1:50 000
|
0.50 km
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approximately 3/4 mi.
|
|
1:60 000
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0.60 km
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approximately 1 mi.
|
Do you need stereo coverage?
Aerial photography is flown so each frame overlaps the previous frame by at least 60 percent. This overlapping area, although
of the same portion of ground, has been photographed from two different angles, providing two different perspectives of
that portion of ground. When adjacent photos are viewed through a stereoscope, the difference in perspective allows the
viewer to see the image in three dimensions, or stereo. Generally, stereo pairs are purchased by engineering and resource
professionals for mapping and interpretive purposes.
Do You Need Pictorial Coverage?
Pictorial coverage provides a complete overview of an area with minimal overlap between photographs by using alternate frames.
The area cannot be viewed in stereo because of the lack of overlap between photographs. The majority of customers are interested
in pictorial coverage.
Contacts
Comments regarding the Air Photo webpages may be directed to:
-
Syd Wood,
Air Photo Distribution Technologist, Air Photo Services
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Updated: May 14, 2010