GIS-based analysis of the impact of proposed construction helped the City of Richmond, Virginia, avert a costly blunder. K. Chul Chong of the Public Works Department discovered that the microwave communication system, used by emergency dispatch units in the city and surrounding Henrico County, would be adversely affected by a tall building in the downtown area that had received approval.
An 800 MHz microwave communication system, consisting of four microwave towers, carries the emergency dispatch calls for all emergency services unitspolice, fire, and ambulancein the region. Any malfunction of this vital communication system could endanger lives. Its proper functioning requires that the signal transmission paths between the four towers remain clear of obstructions.
Chong had analyzed the terrainboth the natural and builtbetween the microwave towers. Because the city GIS did not have building height information for many buildings, he created transmission corridor buffers and used building footprints to identify buildings that fell into the corridor. Footprints for those buildings were assigned exaggerated height values and analyzed in relation to the heights of the transmission tower and the topography of the transmission corridor.
When no impediments to transmission were found in the existing environment, he expanded the analysis to include planned construction. Using building height information and other characteristics of proposed buildings supplied by building permits, he discovered that a 20-story building, which had already been approved, would interrupt transmissions in one of the corridors.
Further analysis revealed an ideal location for the proposed building that would pose no threat to microwave communications. The upshot of the incident was that transmission tower corridor guidelines were developed to allow city decision makers to spot possible conflicts before approval. As a result, the city kept a multimillion dollar microwave transmission system functional, lawsuits were avoided, and the safety of city and county residents was ensured. For more information on GIS use at the City of Richmond, contact
Steve Waldron, GIS Coordinator
City of Richmond