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Delivering Imagery to Mobile Devices

Mark Alonzo

As the level of interest in tactical use of mobile devices increases, so does the desire to provide timely geospatial imagery.  Take, for example, a disaster scenario like Hurricane Katrina.  First responders needed information such as the locations and boundaries of large bodies of standing water.  Responders in command centers could quickly access recently collected imagery with quality communication links capable  of  downloading imagery with file sizes from 300 to 600 gigabytes. And, field-based responders using handheld devices could also benefit from access to the same imagery. However, images files this large can be time-consuming, or impossible, to download over communication links currently available to handheld devices used by field personnel.

Imagery can be delivered to mobile devices by sending specific tiles requested by the user.  Delivering image tiles to handheld devices works, but there are limitations. One of which is the slow process of delivering a small areas in a fixed resolution and the additional requests that occur when the user moves onto a different location.

Requesting JPEG2000 imagery from a server via the JPIP protocol can address these limitations.  With the JPEG2000/JPIP paradigm, the client and server communication automatically handles the requests for additional areas of interest or higher resolution as the end user moves around in the image at the client.  Because the server typically begins by sending a low resolution image that covers a larger area of the image the user can pan around in this image. When a boundary of loaded area is encountered, the server will automatically send additional data to cover the new request.  When the area of interest is found, the end user can zoom in to see the image at a higher-resolution.  This provides a seamless roaming and zooming experience.

When these types of operations are applied, only one or two percent of the original data is delivered from the server to the client, saving the time in the delivery of imagery to mobile and handheld users. And, because such a small amount of data is required, these operations can occur very quickly even across constrained bandwidth and do not require significant storage on mobile devices.

As the demand for imagery on mobile devices increase and as more mobile and handheld devices are operationally deployed, I expect we will see more users find value in the JPEG 2000/JPIP paradigm for working effectively with visual imagery on handhelds  How do you see the use of imagery on mobile devices impacting geospatial analysis applications?

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