Paper No # 852 ,1999 Esri User Conference, San Diego

Authors Names:

Title of Paper:

Energy providers need detailed information about the location and the present technical status of their facilities network. Energy lines often follow rough terrain and therefore permanent monitoring and acquisition of accurate and current data and their management is mandatory.

Esri Germany, TOPOSYS and Rotorflug developed a new technology by integrating airborne laserscanner data into a GIS-based "Powerline Management Information System". The combination of several basic technologies provided by the consortium meets above requirements on accuracy and provides easy access on the database. In more details the system features:

• Digital survey of the terrain structure (incl. vegetation, buildings etc.) by the laserscanner technology of TopoSys (laserscanner data, image data)

• Application of high-end helicopter flight management with helicopters of the company Rotorflug

• Delivery and maintenance of the worldwide leading GIS-Software of the Esri Group to process and integrate geographic and remote sensing data in the computer system of the client

• GIS-Database design, processing and database creation, georeferencing and creation of the Powerline Management Information System by the Planning and Consulting Company Prof. Schaller

The described system solutions are open and compatible. According to clients requirements the provision of pure data, consulting, the software of the Powerline Management Information System or the turnkey complete system (incl. training and maintenance of client�s staff) is available.

1.0 Introduction

The TopoSys laserscanner system is designed to produce digital elevation models (DEMs) of the environment at a typical accuracy of 0.5 m in x, y and 0.15 m in z. The exceptional measurement frequency of 83000 measurements per second results in about five measurements per m� on ground, when surveying from an aeroplane � from a helicopter the measurement density is even higher. This measurement density and the regular scan pattern (parallel lines) form the basis for high quality DEMs.

In the recent years an increasing demand on high-precision digital elevation models (DEMs) has to be noted - high-precision in this sense means that the accuracy of the DEMs is better than 1m in x,y and about 0.2m in z. Many of those applications not only request for high precision, but also demand a short delivery time. Typical applications are monitoring of coastal erosions, simulation of floods in river basins in order to determine engineering works, and simulation of emitter sites or line-of-sight calculations for mobile communication networks.

All the various sensor data (see also Figure 1) are recorded digitally during the laser scanner survey. LINS, GPS, laser data and RGB linescanner data are stored on exchangeable PC harddisks, only video data are stored on a digital tape. During the survey the operator controls the performance of the system, in case of the laser data with help of a real-time waterfall display.

GPS data is registered with help of a Novatel Millennium L1/L2 receiver at a data rate of 1 Hz, while the high precision LINS (Laser Inertial Navigation System) collects position and attitude data at a data rate of 64 Hz. After flight path restitution and merging of dGPS and LINS measurements, position and attitude data are available at 64 Hz.

Figure 1 IHCM System Components

The eye-safe laser sensor operates at 1.54 �m, a pulse rate of about 83 kHz and a scan frequency of 630 Hz. The scan angle is fixed to +/- 7� in order to minimise shading effects especially at the borders of the scan. From a survey altitude of 1000 m the swath on ground is about 250 m. Swath width � and measurement density � can be adapted by selecting the appropriate the survey altitude.

The down-looking video camera, which was part of the sensor package up to now, is replaced by a four-channel linescanner (R, G, B, IR). The linescanner provides a pixel size of about 0.4 m from a survey altitude of 1000 m and allows generating "ortho-photos" of the survey area. The line-scanner data are expected to support the identification of vegetation, too.

The application "Integrated Helicopter Corridor Mapping (IHCM)" is done from a helicopter like a Bell Jetranger 206. In case of IHCM, a 45� forward looking digital video camera additionally records a video sequence of the surveyed tracks (see also Figure 2). Typically survey altitudes in IHCM applications are between 200m and 500 m above ground.

Figure 2. IHCM Sensor Package in a Helicopter

The off-line data processing is done by high-end PCs. Key software packages are a package for flight path restitution and the TopoSys software for DEM generation and post-processing; IHCM post-processing is made by a special package in ARCINFO environment.

The present TopoSys I system will be replaced by the TopoSys II series in late autumn 1999. Performance parameters of TopoSys II are given in the following table.

Table 1. Performance Parameters of TopoSys II

3.0 DEMS FOR VARIOUS APPLICATIONS

Some applications in which TopoSys DEM are used as basic data are urban and environmental planning, simulations of floods and powerline surveys. The following examples of projects have been chosen to illustrate the quality and capability of laserscanner DEMs.

1. 3D City Models

Figure 3. City Model of Karlsruhe, Germany

The vicinity of the city of Karlsruhe was surveyed 1998. Figure 3 shows a 3-D presentation of the DEM raw data, which are overlaid by a scanned orthophoto. The DEM still includes vegetation and buildings, however, these objects can be removed by semi-automatic filtering to receive the classical digital terrain model DTM.

Except from mobile communication applications, such models are needed for simulation of floods and also as basic data for virtual reality purposes.

3.2 DEMs of river basins

Simulation of floods is often done by means of profiles across a river basin. The classical way to get such profiles is terrestrial surveys; aerial photography is often difficult because river basins are mostly covered by vegetation. Due to the ability of laserscanners to penetrate the vegetation, profiles may also be derived in presence of.

Figure 4 shows a part of a river basin and two raw profiles extracted from the DEM. Both the ends of the raw profiles are in dense forest areas, however, there are still enough measurements on the forest floor to reconstruct the shape of the ground surface by some interactive work.

Figure 4. DEM of a River Basin and Extracted Raw Profiles

3.3 Integrated Helicopter Corridor mapping

"Integrated Helicopter Corridor Mapping" (IHCM) is an application developed by TopoSys GmbH, Esri Germany and Rotorflug to survey medium and high voltage powerlines. IHCM integrates airborne laserscanner data into a "Powerline GIS- and Management Information System". Depending on a client�s requirements a spectrum of services is available, from the delivery of the pure data to turnkey systems including maintenance and training of staff.

Figure 5. DEM Of A Medium Voltage Powerline

Figure 5 shows the DEM of a medium voltage powerline as relief presentation. Cross sections and trans-sections may be generated to visualise the distance of vegetation to powerline. However, only line parameters are extracted interactively, the vegetation distance map and the vegetation management plan is created mainly automatically.

Figure 6. Laserdata Integrated In A GIS Environment

The example in Figure 6 shows laserscanner data as background information in a "Powerline and Vegetation Management System". Hotlinks allow cross-references such as links to databank information on CAD drawings of poles or to the video scenes recorded by the 45� forward looking camera.

Another output of the system is a "Vegetation Management Plan" which provides medium term clear-cutting information derived from laserscanner data and vegetation growth classes.

References:

Proceedings of the Fourth International Airborne Remote Sensing Conference and Exhi-

Authors Information:

Prof.Dr. Joerg Schaller

Scientific Director

Esri Germany

Ringstrasse 7

D-85402 Kranzberg, Germany

Phone: +49-8166-677-0

Fax: +49-8166-677-111

Email:J.schaller@Esri-Germany.de

Dr .Uwe Lohr

TopoSys GmbH

Managing Director

Freiherr-vom-Stein-Str. 7

D-88212 Ravensburg, Germany

Phone: +49-751-36605-0

Fax: +49-751-36605-31

Karl Mannheim

Managing Director

ROTORFLUG GmbH

Peter-Geibel-Strasse

D-61365 Friedrichsdorf

Phone: +49-6007-9141-0

Fax: +49-6007-9141 - 24