EM 1110-2-2907
1 October 2003
l. Data Resolution. A major consideration when choosing a sensor type is the defini-
tion of resolution capabilities. "Resolution" in remote sensing refers to the ability of a
sensor to distinguish or resolve objects that are physically near or spectrally similar to
other adjacent objects. The term high or fine resolution suggests that there is a large de-
gree of distinction in the resolution. High resolution will allow a user to distinguish small,
adjacent targets. Low or coarse resolution indicates a broader averaging of radiation over
a larger area (on the ground or spectrally). Objects and their boundaries will be difficult
to pinpoint in images with coarse resolution. The four types of resolution in remote
sensing include spatial, spectral, radiometric, and temporal.
(1) Spatial Resolution.
(a) An increase in spatial resolution corresponds to an increase in the ability to
resolve one feature physically from another. It is controlled by the geometry and power
of the sensor system and is a function of sensor altitude, detector size, focal size, and
system configuration.
(b) Spatial resolution is best described by the size of an image pixel. A pixel is a
two-dimensional square-shaped picture element displayed on a computer. The dimen-
sions on the ground (measured in meters or kilometers) projected in the instantaneous
field of view (IFOV) will determine the ratio of the pixel size to ground coverage. As an
example, for a SPOT image with 20- 20-m pixels, one pixel in the digital image is
equivalent to 20 m square on the ground. To gauge the resolution needed to discern an
object, the spatial resolution should be half the size of the feature of interest. For exam-
ple, if a project requires the discernment of individual tree, the spatial resolution should
be a minimum of 15 m. If you need to know the percent of timber stands versus clearcuts,
a resolution of 30 m will be sufficient.
Table 2-7
Minimum image resolution required for various sized ob-
jects.
Resolution
Feature Object
(m)
(m)
0.5
1.0
1.0
2.0
1.5
3.0
2.0
4.0
2.5
5.0
5.0
10.0
10.0
20.0
15.0
30.0
20.0
40.0
25.0
50.0
(2) Spectral Resolution. Spectral resolution is the size and number of wavelengths,
intervals, or divisions of the spectrum that a system is able to detect. Fine spectral resolu-
tion generally means that it is possible to resolve a large number of similarly sized
wavelengths, as well as to detect radiation from a variety of regions of the spectrum. A
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