The decision depends on the nature of the application and on the means of wireless communication used. The Army has its own radio communications network to keep in contact with handheld devices, making it easy to maintain constant communications. Another shortcoming with wireless communication is a dearth of bandwidth, which is needed for moving data-heavy images to the portable devices. Various solutions are available to address the problem, including transmitting only new, changed data rather than the entire map when updating. That is the approach used by Argonne National Laboratory s Dynamic Object Oriented GIS site, which displays map data.
More detail is available by drilling down into the representation.
This is possible because the map is interactive rather than static. Another option for saving bandwidth is image-compression technology, which makes images easier to download. Xippix Inc. has developed an image-management tool called Image Pump, which lets agencies post interactive maps on the Internet using relatively little bandwidth, for faster loading. It is important for maps to be dynamic, letting users zoom in on the details that interest them, because they tend to cover large areas of territory that aren t of interest. Ultimately, faster digital cellular data transmission speeds will be available, but widespread deployment of such systems is at least several years off, Sonnen said.