OGC GeoPackage: Expanding the Realm of Geospatial Capabilities
This guest post was contributed by: David Wilson, Geospatial Engineer Strategic Alliance Consulting, Inc.; and Micah Brachman, PhD Lecturer, Center for Geospatial Information Science University of Maryland, College Park.
Viewshed using the UK Ordnance Survey Elevation GeoPackage. Image from: OGC 16-094r3 GeoPackage Elevation Extension Interoperability Experiment Engineering Report.
An OGC GeoPackage is a portable database that may contain raster maps and imagery, vector features, and elevation data. GeoPackages are optimized for sharing and displaying these types of geospatial data on mobile mapping systems, and GeoPackage extensions may be developed to support additional types of geospatial data such as routing networks. This blog post will discuss what GeoPackage extensions are, how they are developed, and how they can provide new geospatial capabilities to meet the requirements of a diverse user base.
A GeoPackage extension is method by which new requirements are added to the existing set of requirements in the OGC GeoPackage Encoding Standard. These new requirements expand upon the existing capabilities of GeoPackage by enabling the use of additional data types, styling, and other geospatial functions through the addition of tables, rows, and columns to the existing standard. Extensions can enhance existing capability of GeoPackage (i.e. incorporating Non-Linear Geometry Types) or add a completely new data type entirely (Elevation, Other Media, etc).
Anyone can extend GeoPackage to fit their needs, but custom extensions can come with their own set of interoperability risks. In OGC, extensions must be approved to be “Registered-Exenstions” under the GeoPackage Encoding Standard. A “Registered Extension” is one that’s been vetted through the GeoPackage Standard Working Group (SWG) and has undergone community exchanges and interoperability experiments. This ensures that the broadest scope of industry, academia, and government consumers of GeoPackage participate and influence the outcome of the extension.
GeoPackage extensions are usually developed to fulfill a specific need. The Extension for Tiled Gridded Coverage Data was developed specifically to support terrain visualization and analytics such as line-of-sight on cell phones and other lightweight, low-powered computing devices. The first step in developing this extension was a whitepaper entitled “Envisioning a Tiled Elevation Extension for the OGC GeoPackage Encoding Standard” which identified uses cases, defined terms, and proposed a technical approach for the adding tiled gridded elevation data to a GeoPackage. This whitepaper was discussed and approved within the GeoPackage SWG, and was then socialized with the broader OGC community to build a consensus on the technical approach. An OGC Interoperability Experiment (IE) - known as the GeoPackage Elevation Extension Interoperability Experiment - was then conducted, which included participants from industry, government, and academia to build and test prototype GeoPackages that included tiled gridded elevation data. The technical approach continued to be refined as to not limit the scope the extension. A report of the IE is available here.
There are many other GeoPackage extensions that have been developed in addition to the Tiled Gridded Elevation Data extension. The latest version of the GeoPackage Encoding Standard has eleven Registered Extensions, including an RTree Spatial Indexes extension to improve the rendering performance of large vector feature GeoPackages and a Metadata extension to allow additional information about vector or raster data to be stored within a GeoPackage. While most of these registered extensions provide a method for improving upon the existing capabilities of OGC GeoPackages, there are also several custom extensions that truly expand the geospatial capabilities of GeoPackages.
All in all, GeoPackage is a dynamic product format that will continue to be extended and improved. However, with as many great concepts for possible extensions, OGC’s top priority will always ensure that extensions do not break interoperability and open to everyone to implement.
David Wilson Bio:
David Wilson is a Geospatial Engineer for Strategic Alliance Consulting, Inc that specializes in Geospatial interoperability with a focus on GeoPackage standards compliance, testing and use. David has over 10 years’ experience working in the Army and the National Geospatial-Intelligence Agency’s (NGA).
Micah Brachman Bio:
Micah Brachman is a Lecturer in the Center for Geospatial Information Science at the University of Maryland, College Park. He holds a PhD (2012) and MA (2009) in Geography from the University of California, Santa Barbara and a BS (2000) in Geography from the University of Minnesota. Micah has extensive professional experience in GIS and Remote Sensing in the commercial, government, and non-profit sectors, and recently transitioned from a Geospatial Scientist position supporting the Army Geospatial Center to teach in the new Geospatial Intelligence (GEOINT) program at UMD. In addition to GEOINT, Micah is also actively engaged in teaching and scholarship in Hazards and Emergency Management, Network Science, and Active Transportation.