Technical Challenges

Towards Distributed Imagery Access

The National Geospatial-Intelligence Agency (NGA) has leveraged JPEG2000 Interactive Protocol (JPIP, part 9 of the JPEG2000 specification) as a means for network-efficient access to large images.  Systems such as the NGA Commercial Data Service (NCDS) use this protocol to allow users direct access to commercial satellite imagery despite having low bandwidth connections.

NGA has also been leveraging the Open GIS Consortium (OGC) Web Map Service standards for allowing client applications to access imagery and map product holdings.  The power of the WMS specification is that it allows relatively naïve clients to obtain content for a given area with little to no apriori knowledge of what products (specifically imagery or map files) exist within NGA to produce that result.

NGA is looking to find technical approaches that allow images provided as unprojected imagery JPIP streams to be fronted via OGC WMS services using EPSG:4326.  To achieve this goal NGA seeks solutions to:

1. On-the-fly convert raw imagery JPIP streams to rectified/orthorectified imagery JPIP streams.

2. Provides WMS-compliant service interfaces from imagery coming from these streams.

For the first problem, one might look at http://iasdemo.ittvis.com/home.jsp.  This site provides access to JPIP imagery streams.  The Fallujah image example provides a stream that supports transport of the full XML metadata (including Rational Polynomial Coefficients) associated with the DigitalGlobe image.  Conceptually this kind of stream could be processed by a proxy service that orthorectifies the imagery en route to the user.  The user in this approach would simply see an orthorectified stream and have no idea that orthorectification was being performed inline.

In a separate instance a WMS provider could be configured to understand that the source data for WMS calls is really being provided by JPIP.  This may seem like an odd application.  Consider, however, that the communications link between the JPIP servers (ortho or raw) and the WMS server might be extremely slow whereas the WMS Client User and WMS Server might be on a local LAN.  The JPIP cache that could reside within the WMS Server may allow for much more efficient access to data in this manner.

NGA is interested in seeing prototype solutions against these two problems, either as COTS or custom implementations.  If they are of sufficient interest, NGA may explore further work and/or implementation of the solution into its architectures.

Sample datasets of raw commercial satellite images for use in developing prototype solutions are available upon request via an Internet-accessible FTP server. 

NGA is not obligated to evaluate, purchase, or pay for any incidental costs associated with this request.

Contacts:

Jim Long, james.w.long@nga.mil
Todd Ham, todd.e.ham@nga.mil