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e A high frame rate of min. 1 sec providing high image 
overlaps at typical low flying altitudes for corridor surveys. 
e A co-registered NIR channel enabling numerous automated 
classification and object extraction tasks. 
4.2 Processing of RCD30 imagery 
4.2.1. Calibration: The Leica RCD30 data can be calibrated in 
two different ways. The first way is based on a bundle 
adjustment calculation with an image block from a dedicated 
calibration flight whereas the second way is based on a 
laboratory calibration with specially designed equipment and 
software. Both ways lead to the same set of calibration 
parameters. The RCD30 calibration process is described in 
detail in Tempelmann et al. (2012). 
4.2.2. Creation of distortion free multi-band images: Leica 
FramePro rectifies the raw images to distortion free multi-band 
images with a nominal principal distance, using an equidistant 
grid of distortion corrections. In addition, a principal point 
offset correction and the mid-exposure FMC-position from the 
image header are applied. FramePro supports parallelization by 
means of OpenMP. 
4.2.3. Dense stereo matching / 3d point cloud extraction: In 
our research a prototype implementation of Leica XPro DSM 
was used for extracting fully textured dense 3d point clouds of 
the road corridor. XPro DSM is based on Semi-Global 
Matching (SGM) which was originally developed by 
Hirschmüller (2008). SGM was first adapted to the ADS line 
geometry (Gehrke et al., 2010) and has since been modified for 
frame sensors. The core algorithm of SGM aggregates the 
matching costs under consideration of smoothness constraints. 
The minimum aggregated cost leads to the disparity map for a 
stereo pair and subsequently to textured 3d point clouds in 
object space. 
5. INTEGRATION AND EXPLOITATION 
5.1 Georeferencing and co-registration of ground-based 
and airborne imagery 
If ground-based and airborne imagery and their derived 
products such as 3d point clouds are to be exploited within an 
integrated environment, georeferencing and co-registration of 
both data sets plays an important role. For our first experiments, 
the following georeferencing strategy was applied: 
e INS/GNSS-based direct georeferencing of the ground-based 
stereo imaging sensors. 
e Measurement of 3d control point coordinates (e.g. for road 
markings) in the ground-based stereovision software 
environment using the multi-image matching tool (Eugster 
et al., 2012; Huber, Nebiker, & Eugster, 2011). 
e. INS/GNSS-based direct georeferencing of airborne camera 
data using Leica IPAS TC for tightly coupled processing. 
e [Introduction of the control points into an integrated bundle 
block based on directly georeferenced orientation data, 
adjusted using ERDAS ORIMA. 
For optimal georeferencing results, ground control coordinates 
would normally be established based on tachymetric or GNSS 
survey measurements in the local reference frame. However, 
these measurements were not yet available for these early 
investigations. 
79 
5.2 OpenWebGlobe 
The ultimate goal of this project is to incorporate all original 
and derived data from the airborne and ground-based imaging 
systems into a single interactive web-based 3d geoinformation 
environment. Such a software environment would need to 
provide a fully scalable support for: orthoimagery, digital 
terrain and surface models, dense and fully textured 3d point 
clouds, 2d and 3d vector data and most of all perspective 
imagery, both stereoscopic and monoscopic with dense depth 
data. Nebiker et al. (2010) proposed the use of a virtual globe 
technology for integrating all these data types and for fully 
exploiting the potential of such image- and point cloud-based 
3d environments. 
In our research we use the OpenWebGlobe virtual globe 
technology (www.openwebglobe.org). The OpenWebGlobe 
project was initiated by the Institute of Geomatics Engineering 
of the FHNW University of Applied Sciences and Arts 
Northwestern Switzerland (IVGI). It started in April 2011 as an 
Open Source Project following nearly a decade of 3d 
geobrowser development at the Institute. OpenWebGlobe 
consists of two main parts: first, the OpenWebGlobe Viewer 
SDK, a JavaScript Library which allows the integration of the 
OpenWebGlobe into custom web-applications. Second, the 
OpenWebGlobe Processing Tools, a bundle of tools for HPC- 
and cloud-based bulk data processing, e.g. tiling or resampling 
of large geospatial data sets. This pre-processing is required by 
the viewer part to enable fragment-based, streamed download 
and visualization of data (Christen & Nebiker, 2011; Loesch, 
Christen, & Nebiker, 2012). 
6. FIRST EXPERIMENTS: HIGHWAY MAPPING 
PROJECT A1 ZURICH-BAREGG 
6.1 Overview 
The test area consists of a 22 km highway section (Al between 
Zurich and Baregg) with 3 to 5 lanes per driving direction. The 
terrestrial imagery was acquired on the 24™ of September 2012 
in both driving directions using the IVGI stereovision mobile 
mapping system of the FHNW Institute of Geomatics 
Engineering. For this specific mission, the system featured a 
forward looking stereo configuration with 11 MP sensors and a 
sideways looking stereo configuration with full HD sensors. It 
was operated with 5 fps at a driving speed of 80 km/h resulting 
in stereo frames every 5-6 metres. The data was processed using 
the stereovision processing pipeline presented in Section 3.2. 
The same highway section was mapped on the 28" of 
September 2012 using a Leica RCD30 camera on a Pilatus 
Porter PC-6. Due to the winding character of the road 16 flight 
lines with a total of 637 images were flown. The imagery was 
acquired with a NAG-D lense with a focal length of 53 mm at a 
flying height of 400 m AGL and an image overlap of 80%. The 
resulting GSD of the RGBN imagery is 5 cm. The airborne data 
was processed using Leica FramePro and Leica IPAS TC. 
6.2 Airborne and ground-based imagery 
The following figures show the airborne and ground-based 
imagery of a highway section with a bridge crossing overhead. 
The figures nicely illustrate the complementary character and 
perspectives offered by the airborne and ground-based imagery.