The Real-Time Continuum This article originally appeared in Geospatial Solutions Magazine's Net Results column of November 1, 2001. Other Net Results articles about the role of emerging technologies in the exchange of spatial information are also online.
1. Introduction and Glossary   2. Data Flow   3. Indexing Challenge   4. Instant Messaging Conundrum
After the events of September 11th, one thing everyone seems to agree about is that life in the U.S.A. will never be the same. One of life’s changes will surely involve management of real-time spatial data, specifically for tracking moving objects -- people, cars, trucks, trains, emergency vehicles, jets -- for security purposes as well as for the nascent locationbased services (LBS) market. Bit by bit, real-time spatial data is pervading our traditional static spatial applications. This column summarizes the challenges of real-time data processing and surveys the key players offering solutions.

Ephemeral locations. Real-time spatial data are records of the locations of ephemeral real-world events, such as the rapidly changing coordinates of a moving vehicle. The steps in processing real-time spatial data are:

  • capturing information about an event’s coordinates and date- and time-stamping those coordinates using such technology as GPS;
  • transmitting that data to a central machine;
  • storing the information in the organized structure of a database;
  • analyzing the data both as they arrive and statistically over time;
  • if the analyses dictate, sending messages to other systems to inform them of the status of the object being monitored (see Figure 1).
Figure 1: Conceptual diagram of realtime information flow from the event source (GPS device) to a storage point (database) to a userdecipherable message, such as a map or e-mail.
In other words, people’s mobile devices (cell phones, PDAs, in-vehicle systems, GPS receivers) transmit their locations to a central database at regular intervals. The database determines relationships among moving objects (mobile-to-mobile tracking) or between moving and stationary objects (mobile-to-static tracking). If a relationship has significance, the database sends a message to a decision-maker.

Glossary
GPS Global Positioning System
LBS Location-Based Services
PDA Personal Digital Assistant
1. Introduction and Glossary   2. Data Flow   3. Indexing Challenge   4. Instant Messaging Conundrum