Page 26 - GIS for Science: Technology Showcase

STEPPING UP WITH VOXELS MODELING SOILS BENEATH THE NETHERLANDS IN 3D
Chris Andrews, Esri
Geologists, geophysicists, petroleum explorers, and mining experts have known something for years that we have more recently acknowledged in the GIS world. To understand the real world at high accuracy, you must experience and explore it in 3D. Our oceans, atmosphere, and the planet underneath us are rich with diverse volumetric data such as rock or soil types, chemical composition, pollutants, noise, aquifers, and even the distribution of life. Oceanographers, climatologists, and geologists collected data using remote sensing techniques that enabled reconstruction of complex 3D models of real-world systems. Historically, these datasets have often been limited to the purview of scientists or highly technical professions with specialist software tooling to allow them to explore these data.
With the explosion of interest in and capability for 3D in GIS, users have asked for better capability to view volumetric data in their everyday GIS tools. Our users know that access to volumetric data about the world around them can provide higher- accuracy analysis and better understanding of conditions that they can’t physically experience. Access to 3D data in a GIS allows users to easily communicate with non-specialist stakeholders and even enables new types of analyses and workflows that they cannot with traditional 2D GIS. Using 3D in GIS eliminates the need to use complicated recipes and multiple tools to migrate data from the geophysical, marine, or atmospheric world in GIS experiences or to be used with other GIS content.
Many of the data sources and collection techniques for volumetric data are discrete or discontinuous, resulting in data that may be sparsely distributed throughout a physical space. Techniques exist for filling in, or interpolating, gaps in the volume to enable scientists and engineers to infer the characteristics of any 3D point within the volume. ArcGIS® includes a geoprocessing tool for one such technique, called 3D empirical Bayesian kriging.
In 2D, a cell in a grid of raster data is referred to as a pixel. In 3D, we can group interpolated regions into a 3D raster grid. We refer to the cells in this grid as volumetric elements, or voxels. Voxelization techniques can generate extremely large datasets that are difficult or impossible to view in traditional GIS applications. Academic institutions, petroleum exploration companies, and scientific organizations typically use highly specialized software and hardware systems to view massive voxel datasets. Groups with casual interest in the content, and even less-specialized stakeholders in the same company or organization, often cannot use these expert applications.
ArcGIS can consume volumetric content derived from scientific analysis and remote sensing technology and allow users to display that content alongside any other GIS data. In the ArcGIS workflow, users can read specific types of georeferenced volumetric information, and ArcGIS Pro will convert that data into a "voxel layer"
that they can view in a standard ArcGIS Pro 3D scene. Voxels often have a pixelated or step-like appearance, but users can symbolize them to appear as more analog volumes or continuous gradients.
By consuming voxel data in a GIS, users can combine voxel layers with other standard GIS data types for visualization, exploration, and analysis. Innumerable examples illustrate the use of volumetric information. Engineers and architects see the potential to have rich volumetric information for soils and rocks in the subsurface under existing or proposed construction. Cities can use volumetric information to examine subsurface information and above ground conditions such as airflow, the effects of heat islands, noise propagation, and aerial pollutants. Marine scientists work in an inherently 3D volumetric space and need better visualization and analysis tools to explore ocean temperature and salinity, freshwater mixing, and the propagation of life throughout the oceans. Even tiny creatures such as plankton occupy massive volumes of water, and ocean currents control their dispersion and aggregation, driven by convection, lunar gravity, and other forces operating on a global scale.
Users should be aware that access to volumetric data can still be inconsistent. In some cases, data simply haven’t been collected or created. In other cases, such as in competitive extractive industries, data may be proprietary or protected. However, many government and academic agencies have started sharing volumetric data that may become increasingly useful as more users consume them along with other geospatial content.
NASA, for example, shares large amounts of atmospheric data from satellite studies of Earth. The Dutch independent research organization, TNO (Netherlands Organization for Applied Scientific Research), aggregates and shares massive amounts of subsurface information for use by academia and industry throughout the Netherlands. TNO has been instrumental in working with Esri to help push the limits of what can be done in GIS software.
ArcGIS applications and data types are being used for more comprehensive visualization, exploration, and analysis of 3D content of all types. ArcGIS can combine point clouds, 3D building models, engineering data, and more traditional GIS content. Volumetric data are becoming increasingly relevant in GIS-focused industries. The engineering and construction market is demanding more accurate context for future development to sustain human population growth and to protect the environment. Scientific agencies require more accurate 3D maps of the oceans and atmosphere to combat climate change. Mineral and energy companies use GIS and 3D data to improve target exploration with less environmental impact. Voxel data layers and interactive tools introduce more dynamic, immersive 3D experiences for users to explore, interact with, and analyze the world around them.