Introduction to stereo mapping

Disponible avec une licence Image Analyst.

ArcGIS Pro provides the capability to compile three-dimensional (3D) feature data in a stereo viewing and mapping system. This enables you to visually analyze imagery and accurately collect features of interest.

Stereoscopy is the science of using overlapping imagery acquired from different locations to produce a 3D model that emulates true binocular vision. The technique was developed in the 19th century and more fully developed during World Wars I and II to identify and accurately measure topography and ground features visible in aerial photographs. The main applications of photogrammetric stereo techniques are the identification, measurement, and manual digitization of 3D features from vertical overhead imagery, including the following:

• Buildings, infrastructure, forest stands, and other ground features
• Topography, slopes, landforms, elevation contours, and breaklines due to abrupt topographic discontinuities

Additionally, close-range stereo photogrammetry techniques are used where the sensor look angles are horizontal or oblique to collect accurate, detailed information for primarily engineering purposes, such as mapping the infrastructure of bridges, buildings, dams, and building facades.

Complementing the 3D image view is the accurate overlay of 3D GIS layers on the stereo model, called superimposition. Superimposition techniques use the stereo model to facilitate the manual compilation of land base layers and other vector data with photogrammetric accuracy. Traditionally, the vast majority of accurate land base feature maps have been created and updated using manual 3D stereo compilation, first with optical-mechanical stereoplotters, then analytical stereoplotters in the 1990s, and now with full digital 3D implementations.

Recently, with the advent of high-resolution multispectral imagery and availability of digital elevation models (DEMs) and GPS survey control, land base layers are created and updated using an orthorectified image base. Remote sensing and image processing techniques can be used to automatically identify and classify features at photogrammetric accuracy. However, the advantage of manual stereo compilation is its reliance on the combination of human vision and cognitive abilities to identify and collect features not possible with computer vision and processing. Examples include collecting ground elevation points through tree canopy; compiling buildings, roads, and other ground features obscured by vegetation; collecting important breaklines; and identifying features based on physical 3D attributes and cues.

Benefits of stereo mapping in ArcGIS Pro

The traditional science and art of stereo mapping are mature and well understood. Most accurate and detailed land base layers such as buildings, transportation, utility and communications infrastructure, as well as topography, have been created using stereo compilation techniques. In addition to the ability to collect 3D features in a familiar photogrammetric workflow, the following are important advantages gained by the availability of this capability in ArcGIS Pro:

• An integrated stereo workflow, with no need for a separate photogrammetric package and no data conversion.
• Supports multiple data sources, such as aerial, satellite, and drone images.
• Advanced data model to manage image collection and stereo models.
• Automatic best stereo model detection and flexibility to filter stereo models based on an area of interest.
• Supports both shutter glasses and anaglyph stereo viewing.
• Asynchronous processing enables multiple processes to run in parallel while you compile 3D feature data.
• Fast stereo display accelerated by GPU.
• Advanced editing capability, including feature templates, settings, multiuser concurrent editing, versioning, and more.
• Collects stereo features directly into your GIS database while maintaining topology and data structures.
• Seamlessly integrated 2D stereo pair and 3D features rendering; supports rendering varieties of features and symbols.
• Fixed cursor mode and on-demand, surface-following capabilities facilitate stereo navigation and feature collection.
• Synchronization with maps and scenes provide immediate editing feedback.
• The collected data is immediately useful in the scene view.

Stereo mapping in ArcGIS Pro means that all the data in the ArcGIS platform is both discoverable and immediately useful in your 3D mapping projects. Stereo feature data can flow out to 3D scenes for visualization, as well as back into the stereo view for editing. This data is also immediately available for GIS modeling and useable in time-critical decision support scenarios.

Stereo mapping user experience

In ArcGIS Pro, stereo mapping includes a stereo map viewer that displays and manipulates stereo image pairs from satellite and aerial sensor platforms. The stereo display supports multispectral, three-band, and panchromatic imagery; direct enhancement of imagery; superimposition of 3D GIS data on stereo imagery; zooming and roaming; and other adjustments.

Stereo viewing is facilitated with the use of either red/cyan anaglyph glasses, or active shutter eyewear. In anaglyph mode, the stereo map uses the left image and right image in the stereo model to establish the stereo display, where one band from left image is for red channel and two bands from right image is for the cyan channel.

Stereo Map view, in anaglyph mode. Stereo image pair courtesy of Vexcel.

In shutter eyewear mode, the stereo images are alternatively displayed with high frequency in sync with the active shutter eyewear. The shutter eyewear only allows the left image of the stereo pair to pass through the left shutter lens and the right image to pass through the right lens. The principle is similar to anaglyph glasses, but anaglyph glasses only allow one band to pass through the lens. For shutter eyewear and other hardware requirements please see active stereoscopic viewing kit setups.

When performing stereoscopic visualization on aerial digital, aerial scanned, and drone imagery, any portion of the stereo pair that doesn't have stereo overlap will be masked out. This enhances the stereoscopic viewing experience by maintaining focus on the overlapping region of the stereo pair being viewed.

The photogrammetrically accurate 3D pointer measures and collects ground features directly into feature classes.

The Stereo Map tab contains tools to set up, enhance, and manage stereo models, and superimpose vector GIS data on stereo imagery; ground feature measurement tools; and a Stereo Model Selector pane. The standard feature editing tools can be used for a familiar experience to compile 3D features into feature classes.

If the input images have not been adjusted, ortho mapping tools can be used to perform adjustment and triangulation, and the adjusted mosaic dataset containing the stereo models can be used as input.

Stereo mapping also supports individual stereo image pairs, for example, the image pairs you purchase from satellite data providers.

Integrated stereo compilation

Stereo mapping is included in the Image Analyst extension. Since it is integrated into ArcGIS Pro, it takes advantage of ArcGIS Pro architecture and well established ArcGIS capabilities as follows:

• Adjusted stereo pairs are loaded into the stereo map display in an epipolar orientation for proper viewing and feature compilation.
• Enhance each image comprising a stereo pair.
• Select or define your preferred cursor and its behavior.
• Use dynamic zoom or specify a specific map scale.
• Choose stereo models in the Stereo Model Selector pane by intelligent filtering such as by feature class, interactive polygon, map extent, or attribute.
• Use the ArcGIS Pro editing interface and workflow processes to efficiently define and edit map features, symbology, attributes, and digitizing properties.
• Use predefined feature tables to ensure consistent features for your entire project.

Take advantage of the following feature creation and editing tools, operators, and capabilities:

• Design or use existing feature templates.
• Define your preferences and settings.
• Define fields, subtypes, and domains to work with your data models.
• Define data relationships such as spatial joins, relates, and other standard relationships.
• Manage versioning.