geospatiaL 3d gis
This category features innovative projects that demonstrate the creative
and resourceful use of Bentley technology to spatially model and design
aspects of the real world using 3D representations and visualization.
True Orthophotography and 3D Model of the City of Melbourne aamhatch WINNER
To support planning for the 2006 Commonwealth
Games, AAMhatch created a true orthophoto,
which provides a perfect plan view, where everything is straight up and down, true to size and
scale, everywhere, at all elevations. An image of
each face of the buildings in the Australian city
of Melbourne had to be mapped to a polygon
that would be extruded from the roofline of the
building to the ground. Otherwise, tall buildings
and elevated structures will appear to lean over.
Also, the polygons had to be proportional to
the image so that adjoining faces would align
correctly. To accomplish this, the roofline had to
be projected onto the ground.
More than 600 frames of low-level aerial photography were acquired under specific environmental
conditions to minimize shadows and reflections
from buildings. Airborne laser scanning generated
200 million data points through measurement of
2,500 buildings. In all, the project accumulated
more than 500 gigabytes of data.
Melbourne has incorporated the 3D city model
as a layer in its EView GIS browser. Users find that
features displayed in the imagery are accurate
to one-tenth of a meter of their true ground-level
position. The model enabled planners to evaluate
routes for various Commonwealth Games road
events.
The city also uses it for purposes such as comparing
cadastral boundaries with built forms for land
valuation, managing assets in the city’s Docklands
area, and assessing major building proposals. The
model serves as an image archive that enables
users to roll back to view conditions prior to a
change — for example, before a building was
demolished. With the help of MicroStation VBA
macros and GEOPAK, AAMhatch was able to
generate in minutes what would have taken 400
hours using manual plotting.
