How hybrid airborne data supports sustainability initiatives

Author: John Welter, President Geospatial Content Solutions

Accurate digital representations of our world play an essential role in creating a sustainable future. Rich digital twins and 3D models provide a new level of detail that is ideal for monitoring ecosystems, simulating changes, and making informed choices.

In the past years, we have learned just how unpredictable the world is. Having current rich digital twins at hand enables us to react to emergencies better and more quickly, and compare the past with the present to predict the future. For the most effective analytical results, digital twins need to be collected regularly and fast. Hexagon’s airborne sensors and software support the planning of smarter, greener, liveable cities by providing high-productivity tools to achieve more frequent updates and enabling in-depth analysis with AI and machine-learning.

Why hybrid data?

Only accurate digital twins with a high level of detail support reliable planning. Image-based 3D models — even densely matched ones — have data gaps, for example in narrow, occluded areas between buildings, in shadow areas or under trees. Imaging data can also deliver dissatisfying results for smooth surfaces such as water or untextured roads. Introducing a second data source significantly improves the accuracy and quality of 3D models and meshes.

Hexagon developed the Leica CityMapper-2 airborne mapping system to produce high-resolution hybrid data from two complementary technologies: photogrammetry and LiDAR. It is equipped with two nadir cameras (RGB/NIR), four 45-degree oblique cameras (RGB) and a Hyperion 2+ LiDAR sensor. The built-in mechanical forward-motion-compensation, which is unique to Leica Geosystems’ airborne sensors, enables sharp images even in low-light conditions and at high flying speeds. The 2 MHz linear mode LiDAR delivers three-centimetre range accuracy and is optimised for data collection in urban environments.

Hybrid data offers the best of both worlds. Optical images have high point accuracy in the X/Y plane, while LiDAR has high accuracy in the Z component. LiDAR adds accuracy to mesh models as it penetrates foliage and detects objects in shadowed areas between buildings. Optical works well for top-surface models, and four-colour images are preferred for interpretation, although building facades, roads, transitions and water appear smoother with the aid of LiDAR. Digital twins based on hybrid data contain greater detail and consistency, which provide ideal training data sources for standardised, accurate, large-volume analytics, feature extraction and machine learning.

Mapping with hybrid data

The high-performance workflow software, HxMap, is fully integrated with Leica CityMapper-2 for fast, efficient and intuitive data processing. Within one single interface, the HxMap product generator produces a wide variety of deliverables from the image and LiDAR datasets, including referenced images, orthophotos, colourised point clouds and DSMs. 3D and mesh models come alive with textures added from oblique imagery.

Users can also enhance the 3D model with comprehensive Geographic Information Systems (GIS) data and Building Information Modelling (BIM) data to create a digital twin of the inside and outside of buildings and the surrounding topography. In effect, the real world is converted into an exact digital replica to facilitate analysis, planning and management.

Using 3D models for sustainable development

One focus of many city governments is to transform their cities into sustainable living spaces. 3D models and meshes can be analysed to compare conditions over time and simulate possible future scenarios. Visualising development plans in 3D helps stakeholders understand the consequences of interventions, comprehend interrelationships and recognise planning errors at a pre-investment stage.

Urban planners can work with digital twins to identify suitable areas for green belts or fresh air corridors. The models support the optimal design of critical infrastructure such as energy grids, decreasing the risk of outages and increasing energy efficiency.

Vegetation and green spaces are vital to the health and well-being of city dwellers. In a digital twin, trees are modelled and monitored for health, clearance from power lines, changes in biomass, etc. Early detection of disease prevents the loss of vegetation.

Simulations also help prepare for natural disasters, such as floods and fires, by helping to identify risk areas and evacuation routes, uncovering weaknesses in emergency services and detecting vulnerable supply lines for fuel and food.

The myriad applications for digital twins and 3D models are supported by the hybrid oblique imaging and LiDAR solutions made possible by the Leica CityMapper-2, paired with the HxMap processing platform.

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