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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol XXXV, Part BS. Istanbul 2004
0.9
0.8
0.7
0.6
0:5
AMTF
0.4
0.3
0.2
0.1
9 005 010 015 020
Optech ILRIS-3D
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Cutoff Frequency (pn.
Cutoff frequency threshold (= 2 / x)
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Spatial Frequency (cycles / mm)
Figure 4. AMTF, at 50 m for four TLS systems.
Furthermore, the system offering the finest sampling interval
bad the largest EIFOV and, therefore, the lowest resolution due
to its broad beamwidth.
Some rules of thumb can be derived from the numerical results
presented herein. When the sampling interval is much larger
than the beamwidth, it is equal to the EIFOV. This is the only
condition under which sampling interval accurately represents
resolution. When the sampling interval is approximately 55%
of the beamwidth, the latter equals the EIFOV, the only
condition under which beamwidth accurately describes
resolution.
These observations should not be interpreted as criticism of the
scanner systems themselves or their inventors. The engineering
skill required to develop a working scanning system is indeed
impressive. Rather. the message to be gained by readers is that
resolution is a function of both sampling interval and
beamwidth and, as a result, the attainable resolution of any
system will invariably be coarser than is indicated by either of
these measures. Thus, the more appropriate EIFOV should be
used to measure resolution.
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