Finding Stereo Pairs with the PDS Planetary Image Locator Tool (PILOT)

Introduction: Creating a topographic model is often the first step in performing research such as slope and roughness analysis; landing site determination; wind, water, landslide and lava flow modelling; orthorectification for cartographic products, anaglyph creation, simulated 3D flyovers, and more [1]. Researchers in pursuit of topographic models have developed one-shot stereo-matching tools for specific targets, regions, instruments, and data sets; but as of yet, members of the planetary scientific community have not devised a flexible and comprehensive stereo-matching tool. The Planetary Image Locator Tool (PILOT) [2] aims to fulfill this need with its new stereo-matching feature. PILOT is equipped with a web-accessible easy-to-use interface to locate and evaluate stereo pairs, quickly performing evaluations that require instrument-dependent specifications for culling the data. The tool has the ability to search current data from mission archives, easily adjust constraints (including resolution, incidence angle, emission angle, intersect area, convergence angle and other photometric keywords), and allow further culling of the data through online visual assessment of imagery and geometry. Background: PILOT is a web-based search interface (http://pilot.wr.usgs.gov) supported by the USGS Astrogeology Science Center and the NASA/USGS Planetary Data System (PDS) Imaging Node. PILOT provides access to NASA’s largest archive of spacecraft imagery, the PDS Imaging Node. Searches performed through PILOT are simplified by a planetary mapping interface and an advanced constraint panel to allow easy and incisive culling of the archive data. Searches are further enhanced by sourcing the geospatial information, thumbnail and browse images, metadata and photometric keywords stored in the Unified Planetary Coordinates (UPC) database [3]. Usage: PILOT’s stereo-matching tool was developed to locate stereo pairs over targeted regions, not entire planetary bodies. To maintain the speed and responsiveness of the tool, accessing the tool is restricted to successful PILOT searches with less than 250 images. If an area of interest contains greater than 250 images, further restrictions can be set by defining a latitude/longitude bounding box (map tab) or setting limits for photometric values (advanced tab). To activate the stereo matcher, the user must select the tab marked Stereo at the top of the display. Once selected PILOT computes all possible spatial intersects for the search results. An interactive panel (Figure 1, lower half) slides open and displays the intersects along with options to select and map specific pairs. Information such as convergence angle, intersection area and the variance between photometric keywords (e.g. solar azimuth, emission angle, etc..) are provided through the interface.