TopoSys Streamlines Creation of True Digital Orthos and 3-D City Models

TopoSys GmbH, Biberach, Germany, has developed a line of turn-key, LIDAR/Imaging systems and software that provides a fast and cost effective solution to gather, process, and generate final deliverables such as true digital orthos and digital 3-D city models.

Unlike conventional ortho images, in true ortho images vertical walls of buildings are correctly projected and roofs are not offset. In order to accomplish this, the image data is blended with the elevation model, both of which are acquired simultaneously by the TopoSys LIDAR/Imaging systems. The capability to acquire, and record,  digital image data in four spectral channels, synchronously, with high point-density LIDAR, provides the capability to compute all captured objects in their correct position without leaning edges.

The TopoSys systems are comprised of a family of three sensor systems: The Falcon III, Harrier 56/G3, Harrier 24, and TopPIT processing software.
 
The Falcon III utilizes a unique, technologically advanced fiber-optic linear array LiDAR sensor with an effective measurement rate of 125kHz and an integrated four-channel (R, G, B, NIR) optical line scanner, providing the capability to simultaneously acquire high-resolution, multi-spectral imagery plus elevation data.

Harrier 56/G3 represents the leading edge in LIDAR scanning and digital image acquisition. Full-Wave-Form echo digitization, 200 kHz pulse rate Riegl LMSQ560 Laser scanner combined with a calibrated 39M pixel camera. Harrier 24 is an optimized entry-level system for helicopter-based mapping with the combination of a calibrated 39M pixel camera and a low-cost 10 kHz Laser.

With achievable point densities from between 10 to 40 points per square meter, overlapping measurements and a consistent, specific scan pattern, the precise classification of objects such as buildings, railways, power line cables and other structures becomes routine. The simultaneous acquisition and recording of very accurate, high point-density, digital elevation data and the associated color information from the imagery provides all the captured objects in their spatially correct positions without leaning edges.

Cities Recognize Value of LIDAR and Imagery for 3D Models

The generation of a 3D city model is based on the conversion of aerial LIDAR and image data into vector data to generate 3D block models and roof forms. True ortho imagery is a fundamental building block in the generation of 2-D building footprints which are then extruded to the building heights and roof shapes defined by the LIDAR data. Building facades are then superimposed on the models for photorealistic representation and visualization.

Increasingly, medium and small sized cites are putting out RFP’s for 3D city models. These entities recognize that LIDAR and image data are ideally suited for the creation of accurate 3D city models, with buildings and infrastructure accurately positioned, and that this information has tremendous benefits in a wide variety of urban planning applications, such as:

• Mapping of buildings and their heights
• Line-of-sight and view shed analysis
• Simulation of new buildings and developments
• Security and Intelligence
• Updating and keeping cadastral data
• Sound propagation and noise control
• Tourism
• Tree registers
• Radio network planning
• Pervious and impervious surface inventories

Additionally, the 4-band, multispectral, true-ortho imagery enables the analysis of the spectral reflection of vegetation, non-vegetation, pervious/impervious surfaces and other land-use and cover.

TopPIT Automates Process to Generate True Ortho Imagery

All three sensor systems are complemented by TopPIT, the Lidar processing software developed by TopoSys to support hardware specific pre-processing and streamline data for DEM and true ortho-image production. TopPIT outputs LAS, ASCII, and ESRI shape files. It will co-register the RGB/CIR imagery together with the LIDAR data and uses the DEM to rectify "true" orthophotos in one production flow within TopPIT.

The image data initially comes in uncorrected form in individual strips, and is rectified and georeferenced with the aid of the elevation model. To create true ortho images, the image data is blended with the elevation model from the LIDAR data recorded synchronously with the image data. A presentation in true ortho image projection is achieved by the use of the DSM digital surface model. Unlike conventional ortho images, vertical walls of buildings are correctly projected and roofs are not offset. The single strips are then radiometrically balanced by way of statistical brightness and contrast adjustments and are combined to form a homogeneous image mosaic.

The digital elevation model generated from the laser data and the RGBI scanner files synchronized with the flight position data serve as input for the ortho image computation. In addition to the ortho image computation of the flight strips, the geocoding of the measurement points is directly performed. The result is a high-resolution ortho image in the state plane coordinate system, resolution in the 0.2 – 0.5 meter range, and four spectral channels: Blue = 450 nm - 490 nm; Green = 500 nm - 580 nm; Red = 580 nm - 660 nm; Near infrared = 770 nm - 890 nm. Since the production process is automated, the data can be turned-around very quickly.

About TopoSys:

TopoSys Topographische Systemdaten GmbH was founded in 1995 as a spin-off of Dornier GmbH, one of the world’s leading air- and spacecraft manufacturers.  Building on its long-standing expertise in the development and production of fibre-optic LiDAR scanners, TopoSys is committed to the manufacturing and worldwide marketing of turnkey LiDAR systems that include three newly developed products: Falcon III, Harrier 56 and Harrier 24.  TopoSys offers a well-balanced family of sensor systems, allowing its customers to deliver all LiDAR applications from precise, wide-area topographic mapping to high-density corridor mapping. In February 2007, TopoSys North America, Inc. was established as a wholly-owned subsidiary with North American headquarters in Denver, Colo.

For more information, please visit: http://www.toposys.com

Contact:

Roland Mangold

Director, Business Development
TopoSys North America Inc.
4600 South Ulster Street,

Denver CO 80237-2882

Mobile: 720-934-2482

Phone:    +1-888-438-1208

r.mangold@toposys.com