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Orthophotography
Orthophotography is an ideal tool for the
user who wishes to see and use imagery either as a stand-alone
product or as a background for vector data.
An orthophotograph is a corrected image
from which direct measurements can be made as on a
map.
Orthophotographs are created by draping the imagery over
a DTM or surface model to remove the effects of relief. Laser
scanning data, either from the air or the ground, may also be used
as the surface model.
For larger projects, a block of images
will be corrected and mosaiced to provide a seamless
orthophotograph.
| Example Project: Samir Oil
Refinery, Morocco |
| Brief: To produce an orthophotographic mosaic of the Samir
Oil Refinery, Morocco, prior to the upgrading of the site. The
photography was required to be of sufficient resolution to
form a precise raster, as-built background to the topographic
data. Specifically, the intricate pipe-work had to be
distinguishable. |
Above:
Continuous runs of overlapping aerial photography.
Below:
Aerial photography orthogonally rectified
and mosaiced to create
a precise photomap.
| Three runs
of photography at a scale of 1:12000 were required to cover
the project area. From the stereo photography a surface model
was created from which the orthoimages could be derived with a
ground pixel size of 0.1m. The images were then mosaiced
together using ISM Sysimage software to
create a single photomap of the
area. |
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