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Chapter 9 Remotely Sensed Images from Above
a Site and Association: Site represents the location characteristics of an
item, while association represents relating an object in an image to other nearby features in the image. For example, a football field itself has
enough distinctive features to identify it, but the related phenomena you
could see in the image (the number of bleachers, the number and distribution of the seats, and perhaps the amount of nearby parking) would
help in determining if you’re looking at a field used by a high school team,
a 1-AA college team, or a professional NFL team.
a Size: This is information about the length and width of objects in the image. The relative size of objects in an image can offer good clues in visual
image interpretation. For instance, the average length of a car is about
15 feet. If a car is present in an image, you could compare the length of a
car to the length of other objects to quickly gain information if a structure
is the size of a house or a shopping center. Similarly, some sizes remain
constant throughout images. If objects such as a baseball diamond or a
football field are present, elements in them (the 90 feet between bases or
the 100 yards between goal posts) can be compared to other objects in a
photo to gain relative size information.
a Shadow: This is the shading cast by light shining onto an object. Shadows
also help provide information about the height or depth of the objects that
are casting the shadows. For instance, in the Stratosphere Hotel example,
the height of the tower itself was partially hidden due to the nature of
being photographed from above, but the fact that the object was a very
tall structure was evident from the shadow cast by the tower. Shadows
can also help in determining objects that would be near-indistinguishable
from looking down on them, such as the shadows cast by things like railings or telephone poles.
a Shape: This is the form of objects in an image. The distinctive shapes of objects in an aerial photo can greatly aid in their interpretation. The diamond
shape of a baseball field will help to quickly identify it, or the circular shape
of crops may indicate the presence of center-pivot irrigation in fields. A racing track has a distinctive oval shape, and even an abandoned horse race
track may still show evidence of the oval shape on the landscape.
a Texture: This refers to the differences of a certain tone throughout parts
of the image. The texture of objects can be identified as coarse or smooth.
For instance, different types of greenery can be quickly distinguished
based on texture—a forest of trees and a field of grass may have the same
tone, but the trees appear very rough in an image, while grass will look
very smooth. The texture of a calm lake will look very different from the
rocky beach surrounding it.
a Tone: This is the grayscale (black to white) or intensity of a particular color of objects in an image. The tone of an object can help discern important
information about items in a photo. Like in the Stratosphere example, the
light-blue color of the swimming pool made identifying it easy. Similarly,
a wooden walkway extending into a sandy beach will have different tones
that help in distinguishing them from one another in a photo.
site and association
the information
referring the location
of objects and their
related attributes in
an image. Used as
elements of image
interpretation.
size the physical
dimensions (such as
length and width) of
objects. An element of
image interpretation.
shadow the shadings
in an image caused
by a light source. An
element of image
interpretation.
texture repeating
tones in an image.
An element of image
interpretation.
tone the grayscale
levels (from black to
white) or ranges of
a color for objects
present in an image.
An element of image
interpretation.
shape the form of
objects. An element of
image interpretation.
Chapter 9 Remotely Sensed Images from Above
a Site and Association: Site represents the location characteristics of an
item, while association represents relating an object in an image to other nearby features in the image. For example, a football field itself has
enough distinctive features to identify it, but the related phenomena you
could see in the image (the number of bleachers, the number and distribution of the seats, and perhaps the amount of nearby parking) would
help in determining if you’re looking at a field used by a high school team,
a 1-AA college team, or a professional NFL team.
a Size: This is information about the length and width of objects in the image. The relative size of objects in an image can offer good clues in visual
image interpretation. For instance, the average length of a car is about
15 feet. If a car is present in an image, you could compare the length of a
car to the length of other objects to quickly gain information if a structure
is the size of a house or a shopping center. Similarly, some sizes remain
constant throughout images. If objects such as a baseball diamond or a
football field are present, elements in them (the 90 feet between bases or
the 100 yards between goal posts) can be compared to other objects in a
photo to gain relative size information.
a Shadow: This is the shading cast by light shining onto an object. Shadows
also help provide information about the height or depth of the objects that
are casting the shadows. For instance, in the Stratosphere Hotel example,
the height of the tower itself was partially hidden due to the nature of
being photographed from above, but the fact that the object was a very
tall structure was evident from the shadow cast by the tower. Shadows
can also help in determining objects that would be near-indistinguishable
from looking down on them, such as the shadows cast by things like railings or telephone poles.
a Shape: This is the form of objects in an image. The distinctive shapes of objects in an aerial photo can greatly aid in their interpretation. The diamond
shape of a baseball field will help to quickly identify it, or the circular shape
of crops may indicate the presence of center-pivot irrigation in fields. A racing track has a distinctive oval shape, and even an abandoned horse race
track may still show evidence of the oval shape on the landscape.
a Texture: This refers to the differences of a certain tone throughout parts
of the image. The texture of objects can be identified as coarse or smooth.
For instance, different types of greenery can be quickly distinguished
based on texture—a forest of trees and a field of grass may have the same
tone, but the trees appear very rough in an image, while grass will look
very smooth. The texture of a calm lake will look very different from the
rocky beach surrounding it.
a Tone: This is the grayscale (black to white) or intensity of a particular color of objects in an image. The tone of an object can help discern important
information about items in a photo. Like in the Stratosphere example, the
light-blue color of the swimming pool made identifying it easy. Similarly,
a wooden walkway extending into a sandy beach will have different tones
that help in distinguishing them from one another in a photo.
site and association
the information
referring the location
of objects and their
related attributes in
an image. Used as
elements of image
interpretation.
size the physical
dimensions (such as
length and width) of
objects. An element of
image interpretation.
shadow the shadings
in an image caused
by a light source. An
element of image
interpretation.
texture repeating
tones in an image.
An element of image
interpretation.
tone the grayscale
levels (from black to
white) or ranges of
a color for objects
present in an image.
An element of image
interpretation.
shape the form of
objects. An element of
image interpretation.