HxMap: Simultaneous processing of airborne imagery & LiDAR data

Leica Geosystems airborne sensors, along with high quality and performance, all share another common aspect – they use HxMap, the unified high-performance multi-sensor workflow platform, to process the vast amounts of data captured. HxMap offers rapid data processing updates over large areas in the shortest possible time.

For a deeper look into the versality and benefits of data processing with HxMap, Product Manager Felix Rohrbach explains the one-for-all software platform.

How does HxMap work?
Leica HxMap offers individual software modules based on customer’s processing needs. The modules intuitively guide you along a common processing workflow for LiDAR and image data. Data download, raw QC and data ingest are identical for LiDAR and imagery data sets throughout the pre-processing steps. Sensor-specific modules include further steps like aerial triangulation, radiometric adjustments and LiDAR point cloud registration. The modular approach of HxMap guides the users through the workflow step-by-step with only small variations between the processing of LiDAR and imagery data.

The final step of the HxMap workflow – product generation – allows to output a large number of products by the push of a button, such as:

  • Referenced images

  • Orthophotos

  • colorized and uncolourised point clouds

  • textured and untextured 3D city models

These features lay the foundation for large oblique projects, country-wide orthophoto or LiDAR mapping and small engineering projects alike, and offer full scalability independently from the sensor model used to capture the data.

HxMap is a key element of several Leica Geosystems solutions. Can you explain those solutions?
We refer to Airborne Reality Capture as the combination of data acquisition and data processing. At Leica Geosystems, we have created Airborne Reality Capture solutions bundling HxMap with appropriate airborne sensors for a particular application. This enables our users to reach the highest efficiency and full scalability of the processing infrastructure independently of which Leica Geosystems airborne sensor is used for a project.

RealCity is the combination of the Leica CityMapper or CityMapper-2 hybrid oblique imaging and LiDAR sensor with HxMap. This solution is ideal for 3D city modelling applications and produces 2D imagery products, LiDAR point clouds as well as 3D city models.

RealWorld is the combination of the Leica DMC III frame camera sensor with HxMap. This pairing is best suited for large area imaging projects in 2D.

RealTerrain combines HxMap with either Leica TerrainMapper and Leica ALS80 linear-mode LiDAR sensors or Leica SPL100 single photon LiDAR sensor. This combination is designed for regional and national LiDAR mapping projects.

Within HxMap, there are several modules for specific applications. Can you expand on these modules?
HxMap can be personalized through the addition of modules to fit any user’s unique needs.

HxMap Provider Module offers the user the essential functionality to load collected data, run ingest to pre-process, apply geo-referencing and then visualize the result to perform quality control. The provider module also includes the workflow manager, our main application that guides the user through the various processing steps. Data can either be loaded onto a map view or into a specific viewer module for further inspection.

HxMap Core Imaging Module offers functionality essential to processing imagery datasets. A robust automated point matching generates required tie points between collected imagery across viewing directions. With aerial triangulation will use the measurements to optimize image orientations. HxMap provides multiple triangulation algorithms and a hierarchical process mode for oblique datasets that allows processing of even the largest mapping projects our customers have seen. HxMap triangulation also allows the user to directly apply any misalignment angle to the camera calibration.

HxMap Core LiDAR Module completes the feature set with all functionality required for LiDAR data processing. A simple one-click LiDAR calibration calculates adjustments to the sensor parameters and outputs an updated project calibration for further processing. Line-to-line registration further improves the matching quality across the full project. At any time, the user can run the built-in QA-tool to evaluate data quality for a single line or the full project.

HxMap 3D Modeller Module supplements the previous modules. The 3D modelling algorithm takes imagery and LiDAR data either as standalone datasets or together as hybrid data and extracts 3D building geometries. HxMap allows the user to provide known building footprints to generate buildings or directly run building generation without any prior information. Additional information of provided data sets, like point classes or vegetation indices calculated from imagery data, are used to further improve the quality of the extracted buildings.

How does HxMap benefit the user?
HxMap is a fast, intuitive and efficient post-processing platform, enabling users to produce all known data products within one single common interface. This translates into

  • Full scalability
    With HxMap being a unified processing workflow for airborne topographic LiDAR and imaging data, users can use the same processing infrastructure independently from the project deliverables, offering complete flexibility to scale the processing infrastructure when needed and produce all products. The modular functionality offers our customers the option to keep the initial investment low and scale up the infrastructure if needed, enabling the consistent use of their full processing capacity.

  • Time and cost savings
    You and your staff only need to be proficient in one simple user interface to produce any known airborne data product, and your production workforce can process imagery and LiDAR data without additional training. Don’t waste time moving your data between software packages but benefit from one end-to-end workflow.

  • Unprecedented data throughput
    Take advantage of the industry’s fastest data throughput and process any amount of data more efficiently. HxMap has been tried and tested to process SPL100 data, which captures 6 million points per second and therefore is known to consist of extremely large data sets.

What challenges are users facing in today’s field that HxMap helps them overcome?
Looking back to when I started, it was very common to see single workstation processing environments. The photogrammetry or LiDAR expert would sit in front of their machine that had all the data and software required to run all processing steps locally. Once launched it turned into a waiting game until the process was completed and the next step could be launched.

Challenge 1: Amount of data

Nowadays, any modern sensor will produce mega amounts of data. A rough rule-of-thumb for the original CityMapper was that 1 hour of data collection would produce 3TB of raw data. Even though the amount of data has multiplied throughout the past years, the delivery deadlines of our customers and their end customers have not changed. Despite the increased size, the data needs to be checked, processed and delivered in an acceptable time frame. Thanks to HxMap’s distributed processing capability, this is now possible.

Challenge 2: Data processing silos

Moving to distributed processing can also introduce new pain points. If you operate both imagery and LiDAR sensors, you may face the reality that both workflows require upscaling. Setting up siloed processing environments sounds easy enough, but lead to your resources not be used to their full capacity as soon as data input is halted (e.g. due to bad weather). Thanks to HxMap’s hybrid workflow, distributed processing is setup in one combined environment which can be configured to consume any available capacity independent of data type.

Challenge 3: Human workforce

The last challenge is refers to any of the workflow steps that cannot be handled by our processing cluster. Many of the quality control steps are still executed by humans as their expertise is required to assess if data matches the required quality. The first problem here is that with growing volume of data, more staff is needed to ensure throughput. Finding expert staff though is difficult and costly. HxMap addresses this by assisting the user to evaluate the quality of collected data through graphical representations and customer reports of quality indices that allow even the average user to assess data sets. The processing expert can become the team leader, who is only consulted in this critical edge cases.

There is a focus in today’s market on automation. How does HxMap support this next technology frontier?
The focus on automation is a logical consequence of the above challenges. Turning a previously manual task into an automated processing step allows us to not only run it on a single workstation, but also send it directly to our processing cluster. Besides saving time, money and effort on training, this now allows to scale the production step according to current workload and delivery timelines. HxMap already supports these benefits for processing tasks such as sensor calibration, automatic point matching, line-to-line registration, building generation and many more. All of these were previously tedious manual tasks that can now be run automatically within the HxMap workflow.

Where will HxMap take the industry in the future?
The recent trend of increasing numbers of pixels and points per project will continue. This is not only due to projects flown at higher resolution, but also due to the growth of Content as a Service (CaaS) initiatives such as the HxGN Content Program. While UAVs start covering the need for survey-grade small-scale data acquisitions, airborne surveying is moving towards regional, national or even continental acquisition.

Finding innovating ways to automate processing steps without compromising data quality will be an essential task for turning manual work into scalable and distributable jobs. The use of hybrid data – like collected by the CityMapper sensors – looks promising to improve data quality by merging information from multiple sensor types. Our city modelling engine is a good example where the advantages of both LiDAR and imagery technology is used to efficiently create high-quality 3D products.

Besides making our current workflow more efficient, we are also looking into expanding the range of products our customer will be able to generate within HxMap. Hexagon-wide initiatives as well as acquisitions give us access to new technologies, and it is our task to turn these into innovative products for our customers.

Felix Rohrbach is the product manager for HxMap at Leica Geosystems.
With a decade of experience in the airborne mapping industry, he is responsible for the development and adoption of photogrammetry and LiDAR processing software.

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