A new era of airborne city mapping
Author: Penny Boviatsou
Using a professional workflow solution as part of airborne mapping applications is as important as high-end sensor technology. In urban environments, this becomes even more apparent. They are subject to rapid changes and thus have a higher need for up-to-date data for:
- 1. Navigation
- 2. Planning purposes and
- 3. Visualisation.
In addition, 3D mapping projects over metropolitan areas generate large amounts of data that need to be processed within reasonable timelines.
In order to meet the demand of mapping professionals’ efficient data collection and fast throughput without the loss of quality, Leica Geosystems has introduced Leica RealCity, a tightly integrated solution combining efficient imaging and LiDAR data collection with the Leica CityMapper with the post-processing workflow for high volume production, Leica HxMap.
Acquiring and processing LiDAR data across the US
Leica Geosystems partnered with international asset integrity and geo-intelligence solutions provider, Fugro, to begin acquiring and processing data over multiple cities and coastal regions across the US.
Using CityMapper, Fugro conducted aerial surveys over some of North America’s most densely populated urban centres, in support of their geospatial mapping services. As the world’s first hybrid airborne sensor combining oblique and nadir imaging as well as a LiDAR system into one instrument, the CityMapper enables significant time and cost savings by flying once to collect both imagery and LiDAR data. All collected LiDAR and imaging data can be processed in the one unified workflow solution, Leica HxMap.
“We have a long history working with Leica Geosystems sensors, because they are so reliable. CityMapper has proven no different,” said Mike Wernau, Fugro program manager. “The platform's superior design, coupled with Leica Geosystems’ newest version of HxMap, amplifies our ability to create highly accurate, feature-rich geospatial content.”
The results of the airborne surveys were post-processed using the latest version of Leica HxMap, the unified high-performance multi-sensor workflow. Within a single and familiar interface common to processing other Leica Geosystems airborne sensors, all typical data products, from orthophotos and oblique images to point clouds, 3D meshes and models, can be quickly and efficiently produced.
The latest update of the common-sensor post-processing software sees the addition of LiDAR point cloud generation, calibration, strip matching and viewing to the current image processing capability. Leica HxMap version 2.2 also incorporates enhanced noise filtering for both CityMapper and Leica SPL100 single-photon LiDAR sensors.
“HxMap v2.2 is extremely powerful, as it establishes a single environment to process our CityMapper oblique and nadir imagery, point cloud and terrain data all at once,” said Wernau. “The products derived from the Leica RealCity workflow serve as the foundation for our land and property solutions, delivering real value to our customers in state and local government, insurance, and land-use management.”
Exciting CityMapper results in Bordeaux
The city of Bordeaux is among France's most exciting, vibrant and dynamic cities. It is a port city on the Garonne River in the Gironde department in southwestern France. Together with its suburbs, Bordeaux is the centre of the Bordeaux Métropole with about 760,000 inhabitants.
Bordeaux is the world's major wine industry capital. It is home to the world's main wine fair, Vinexpo and the wine economy in the metro area takes in 14.5 billion euros each year. In 2007, after nearly a decade of infrastructure upgrades, Bordeaux was recognized by UNESCO as a World Heritage site for its vast Enlightenment-era urban core. After Paris, Bordeaux has the highest number of preserved historical buildings of any city in France.
In 2017, APEI (Aéro Photo Europe Investigation), a well-recognised French aerial survey company specialising in the airborne acquisition of geospatial data using innovative techniques and equipment, worked together with the Direction de l'Information Géographique (D.I.G.) de Bordeaux Métropole for Bordeaux’s city mapping project. APEI delivered aero triangulated obliques images captured with Leica CityMapper and Bordeaux will use these images to create a 3D city model.
D.I.G. de Bordeaux Métropole is responsible for managing the reference layers of the Geographic Information System used in the Bordeaux metropolis. The project was flown in only 2 days (10th and 11th March 2017) with a twin piston-engine Partenavia P68C, registered F-HPEI.
“The system uses Leica PAV100 and Leica FlightPro which are part of the Leica airborne common platform. It makes it really easy for our staff to operate and the training has been performed in only 2 hours. We used the Leica PodLifter which is specifically designed to lower the camera into the PAV100 to get full view for oblique capture. It was a very useful feature,” said Bruno Callabat, CEO and technical manager, APEI.
Airborne reality capture
Looking at specific use cases and comparing the results of an image-generated point cloud with a point cloud generated from fused imaging and LiDAR data, the benefits are clear. In many countries up the 35 per cent of urban areas are covered with trees. As such the image point cloud is very dense on the buildings, however the digital elevation models of streets and surfaces under the trees are disturbed. In contrast, the CityMapper’s LiDAR penetrates through the trees and generates an accurate ground model with a flattened ground surface. In areas with shadows on the buildings or with irregular surfaces, the building edges in the image point cloud can be fluffy. With the fused imaging and LiDAR workflow, these edges are much sharper and the models are more accurate.
It is a natural next step to improve image based point clouds with LiDAR-based point clouds, adding accuracy and additional information to help create the best 3D model possible. As urban environments change so rapidly, it is desired that image data and LiDAR data are collected at the same time, a requirement that gave birth to the Leica CityMapper, the world’s first hybrid airborne sensor specifically designed for urban planning application. The simultaneous acquisition of nadir and oblique image data as well as LiDAR data offers the most cost-effective way to generate a comprehensive geospatial base map for city planners and those who are engaged in urban mapping.