A new era of airborne city mapping

作者：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. 导航
2. 计划目的和
3. Visualisation.

此外，大都市区域上的3D映射项目还会产生大量需要在合理时间表中处理的数据。

In order to meet the demand of mapping professionals’ efficient data collection and fast throughput without the loss of quality, Leica Geosystems has introducedLeica RealCity，一种结合有效成像和激光雷达数据收集的紧密集成解决方案Leica CityMapperwith the post-processing workflow for high volume production,Leica HXMAP.

在美国获取和处理LIDAR数据

Leica Geosystemspartnered with international asset integrity and geo-intelligence solutions provider, Fugro, to beginacquiring and processing data over multiple cities and coastal regions across the US.

Fugro使用CityMapper进行了aerial surveys over some of North America’s most densely populated urban centres,在苏pport 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.

“我们与Leica Geosystems传感器合作的历史悠久，因为它们是如此可靠。CityMapper证明没有什么不同，”said Mike Wernau, Fugro program manager.“该平台的出色设计，再加上Leica Geosystems的最新版本的HXMAP，它扩大了我们创建高度准确，功能丰富的地理空间内容的能力。”

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非常强大，因为它建立了一个单一的环境来处理我们的CityMapper倾斜和Nadir图像，点云和地形数据，所有这些都可以。”沃尔瑙说。“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.”

令人兴奋的CityMapper导致波尔多

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 deliveredaero triangulated obliques imagescaptured 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只有2天（2017年3月10日至11日）带有双活塞发动机Partenavia P68C，注册了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.