In the event of an emergency, the information that propels our actions can have a dramatic impact on the situation. The GIS interface depicting the GVRD catchment areas has to consider a number of intelligent structures in order to best utilize the services available. What better place to start than asking what the procedures are for defining a catchment area?

Health Care Facility Catchment Areas are understood as a delicate balance of geographical and demographic information. They take into consideration the physical world - that of roads, rivers, lakes, mountains as well as those areas belonging to the human world - such as populations and municipalities. Though they help establish where hospitals are constructed, they are at a disadvantage because unlike the populations they reflect, they tend to be static geographic boundaries.

During the course of this project, an underlying theme was recognized. That is, how do we address questions pertaining to service zones? The GVRD is particularly interesting in its demographics and remains a challenge to map intelligently. Due to a lack of immediate information during the time of project construction, the following considerations were developed by the researcher:

• What are the sizes of each hospital - the number of beds, staff and nursing support?
• What are the 'traditional' hospitals and which are simply 'extended care' facilities?
• Are all of the facilities still open door - are there any health care facilities that have been shut down?
• What is the total number of physician offices (surgical/non-surgical) within the Catchment area?

In order to properly weigh the variables to create a catchment area, the above pieces of information need to be considered. Due to a lack of immediate and appropriate information, this mapping project only calculated geographical boundaries during the creation of the catchment zones (through Thiessen/Voronoi polygon creation). However, it should be noted that the framework for this mapping project could be adjusted to show more precise catchment areas and their interior influences as more information becomes available.

The process that goes into catchment development are indeed complex. This mapping project simplified hours of project planning by knowledgeable professionals and assumed only geographical weights. However, this was not without its dilemmas. Of foremost importance is knowing the geographic regions that are being mapped through the tessellation process. It was noticed that during the weighted Voronoi calculation, catchment areas that bordered water were often times separated into more than one polygon. This was assumed reasonable for areas in local inlets and rivers containing islands, but was presumed unreasonable if a section of the catchment zone was calculated on the opposite bank of the water body. During the planning phase, these pitfalls need to be recognized as it makes little 'immediate' sense to send a potential victim across more land mass than necessary during an emergency. Below are listed two sample images for further emphasis relating toS this problem.

unweighted GVRD catchments: land weighted catchments:

For additional information pertaining to mapping population clusters click here.