1 October 2003
coarse resolution refers to large groupings of wavelengths and tends to be limited in the
(3) Radiometric Resolution. Radiometric resolution is a detector's ability to distin-
guish differences in the strength of emitted or reflected electromagnetic radiation. A high
radiometric resolution allows for the distinction between subtle differences in signal
(4) Temporal Resolution.
(a) Temporal resolution refers to the frequency of data collection. Data collected
on different dates allows for a comparison of surface features through time. If a project
requires an assessment of change, or change detection, it is important to know: 1) how
many data sets already exist for the site; 2) how far back in time the data set ranges; and
3) how frequently the satellite returns to acquire the same location.
(b) Most satellite platforms will pass over the same spot at regular intervals that
range from days to weeks, depending on their orbit and spatial resolution (see Chapter 3).
A few examples of projects that require change detection are the growth of crops, defor-
estation, sediment accumulation in estuaries, and urban development.
(5) Determine the Appropriate Resolution for the Project. Increasing resolution
tends to lead to more accurate and useful information; however, this is not true for every
project. The downside to increased resolution is the need for increased storage space and
more powerful hardware and software. High-resolution satellite imagery may not be the
best choice when all that is needed is good quality aerial photographs. It is, therefore, im-
portant to determine the minimum resolution requirements needed to accomplish a given
task from the outset. This may save both time and funds.
2-8 Aerial Photography. A traditional form of mapping and surface analysis by re-
mote sensing is the use of aerial photographs. Low altitude aerial photographs have been
in use since the Civil War, when cameras mounted on balloons surveyed battlefields.
Today, they provide a vast amount of surface detail from a low to high altitude, vertical
perspective. Because these photographs have been collected for a longer period of time
than satellite images, they allow for greater temporal monitoring of spatial changes.
Roads, buildings, farmlands, and lakes are easily identifiable and, with experience, sur-
face terrain, rock bodies, and structural faults can be identified and mapped. In the field,
photographs can aid in precisely locating target sites on a map.
. Aerial photographs record objects
in the visible
and near infrared
and come in a va-
riety of types and scales. Photos are available in black and white, natural color, false
color infrared, and low to high resolution.
b. Resolution in aerial photographs is defined as the resolvable difference between
adjacent line segments. Large-scale aerial photographs maintain a fine resolution that