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Orbisat da Amazônia is a leader in the application of
Remote Sensing technology for use in mapping, geomatics, and
geospatial information gathering. The company's expertise
lies in its use of Interferometric Synthetic Aperture Radar
(InSAR), which provides fast, accurate, and cost-effective
solutions for the professional and scientific communities
engaged in activities such as urban and regional planning,
environmental analysis, and resource exploration and mapping.
The CartoSUR II project was established in Venezuela in 2003
as a national cartographic venture to acquire radar-based
mapping data covering approximately 1/3 of the entire country.
Located at the northernmost end of South America, Venezuela
has a total area of 912,050 km². Included in the CartoSUR
II project area was the state of Bolivar, which contains some
of the oldest land forms in South America. The rugged mountains,
steep cliffs, and plateaus, rise to over 3000 m in places,
and contain one of the highest waterfalls in the world, the
Angel Falls. The terrain gradually flattens out and drops
down to the Delta Amarcuro on the east coast. Densely covered
with forest and scored with tributaries of the Rio Orinoco,
this whole region is often under thick cloud cover, and as
such can be a very difficult area to map effectively.
Synthetic Aperture Radar
"With the point cloud density achievable
with LIDAR and the accuracy of the integrated
POS AV system, we were able to precisely position
both terrain data and aerial imagery, which made
for a very efficient workflow."
Dr. Markus Rombach
Commercial Director Orbisat da Amazônia
Orbisat immediately saw the solution to generating accurate
cartographic data for this type of environment. The InSAR
technology, with its all-weather operational capability, is
unaffected by cloud, rain, poor visibility, and ground vegetation,
and can very quickly produce accurate, detailed imagery, including
digital terrain models. Installed aboard a Gulfstream Aerocommander
aircraft, OrbiSAR-1 simultaneously uses two radar bands to
generate image data, a result of the unique response of terrain
and cultural targets to radar frequencies. The X-band reflects
off surface objects such as trees, and buildings etc., to
produce a Digital Surface Model, and the P-band reflects below
the vegetation and produces a Digital Terrain Model.
Within three months of starting the airborne operation, and
700hrs of air time, all image acquisition was completed. Flying
at an altitude of 23,000', and using a dual pass for P-band
interferometry with an 80 m baseline, the 3D imaging data
was generated and made ready for processing. Dieter Leubeck,
Project Manager, Orbisat, explained. "As well as providing
position and orientation information for the radar imagery,
the POS AV system also generates a real-time navigation solution
that is incredibly accurate. We can fly a 120 km line and
stay within a 1m horizontal variance quite easily. These attributes
make the OrbiSAR-1 system extremely effective in undertaking
radar mapping projects, and it's the POS AV that provides
the spatial orientation accuracy." Final data delivery
to the Geographical Institute of Venezuela Simon Bolivar (IGVSB)
totaled 518 map sheets at a scale of 1:50,000, and covered
an area of more than 263,000 km². Contour information
was illustrated on the X-band orthoimage maps, and digital
terrain model and full polarimetric P-band image data was
made available for the complete project.
