Oo direct connection to computers for data checking,
preliminary processing, and data storage
o high precision through precise encoder calibration
ANALYTICAL STEREOCOMPARATORS
Like analytical monocomparators, analytical stereocom-
parators (fig. 5) are for measuring discrete points although
they possess the capabilities of both analytical monocompar-
ators and analytical stereoplotters. They have the following
advantages over analytical monocomparators:
Oo better image definition and identification by stereo-
scopic viewing of imagery on overlapping photos
o superior measuring capability since the floating or
measuring mark setting must satisfy a 3rd dimension
setting (z)
o capability of eliminating errors in transferring
points from photo to photo
oO increased accuracy and more positive identification
in transferring corresponding points from photo to
photo within strips of photos and from strip to strip
in a block of photos since, for 3-plate models, three
photos can be viewed and measured concurrently.
ANALYTICAL MICRODENSITOMETERS
Microdensitometers (fig. 6) digitally record the density
and coordinates of each pixel of imagery within a photo,
providing means for digitally correlating (matching) corre-
sponding images from overlapping photos and for computing
their ground position. Stereomodel parameters can be comput-
ed mathematically, and an orthophoto can be produced with
undesirable displacements and errors removed. The advantages
of analytical microdensitometers over optical-mechanical
orthophoto instruments in producing orthophotos include:
o the capability of producing orthophotos with features
of high relief imaged in their exact true position.
For example, the tops of flag poles can be set pre-
cisely over the base, a virtually impossible feat
with mechanical orthophotos.
o the ability to fill in missing imagery caused by high
relief, either by digitally "faking" imagery or by
filling in from other photos taken of the hidden
areas from more favorable positions
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