By Randy Knippel
Emergency responders have learned valuable lessons from recent disasters such as Hurricane Katrina. We can see the importance of training and preparedness, but are humbled and awestruck by the damage and destruction. Responders to these disasters quickly realized that they needed current maps and a common knowledge about using them. A little additional effort has led to some dramatic improvements in these areas.
One such improvement is called the United States National Grid (USNG). The National Grid creates a universal, scalable referencing system for any location in the United States and beyond. The Federal Emergency Management Agency (FEMA) and the Federal Geospatial Data Committee (FGDC), as well as many state and local governments, have adopted it as a standard. It is currently proposed as a Minnesota standard. What this means is that, with proper training, all emergency responders will be able to speak the same language when referring to a location, regardless of where they are or where they are from. They will expect to have current maps that include the National Grid at standard scales to support their efforts for navigation, measurement, resource deployment, and status communication. The maps will be interoperable across jurisdictions and among local, state, and federal government agencies.
The National Grid has actually been around for a while. It was originally identified as a potential standard after Hurricane Andrew in 1992, but its origins are with the Military Grid Referencing System (MGRS), which has been around since World War II and continues to be the military standard. The MGRS and the USNG use the Universal Transverse Mercator (UTM) projection and coordinate systems, with a different notation to make it easier to learn and use.
UTM divides the surface of the earth into zones of 6 degrees of longitude that stretch from pole to pole. The USNG subdivides each of these zones into rectangles, each covering 8 degrees of latitude. Each of these USNG zones is then given a unique alphanumeric identifier. Minnesota is mostly contained by zone 15T, with parts in 5 adjoining zones (Figure 1).
Figure 1 - 6 degrees longitude by 8 degrees latitude grid zones over MinnesotaEach zone is then divided into 100,000-meter squares, based on UTM coordinates, and given a two-character designation formed by rows and columns of single characters. Therefore, Dakota County falls in VK and WK, or, using the full USNG designation, 15TVK and 15TWK (Figure 2).
Figure 2 - 100,000m grid designations with 10,000m grid lines over Dakota CountyAny location within the 100,000-meter squares is referenced as an offset in meters from the lower left corner of the square, starting with zero, measuring right, then up. Therefore, my current location is 15TVK 83399 53353, which can be easily interpolated or measured using grid lines (Figure 3).
Figure 3 - 100,000m-grid designation with 1,000m grid lines over part of Apple Valley The real power of the USNG becomes apparent when we see it referenced at various scales. If a major tornado hit Dakota County from Burnsville to Coates, we can simply say that the affected area is in 15TVK and military resources or volunteers from anywhere will know where we are and that the damage is contained within a 100,000-meter square. That can be further refined to say that the tornado path included VK7050 to VK9050, isolating it further to three 10,000-meter squares. Again, anyone with USNG training will know where that is and be able to begin to acquire maps and plan their deployment. At a detailed level, resources can be deployed by simply using an abbreviated notation representing 1,000- or 100-meter squares. Therefore, if a search operation is contained in 15TVK9751 (1,000-meter square), individuals or teams can be assigned 100-meter squares within that area with simply a two-digit designation.
The Grid also creates a convenient mechanism for tracking resources and status of a response and recovery effort. Based on the extents of the effort, grid cells can be easily selected at varying resolutions of 10,000, 1,000, 100, or even 10 meters and used to record activities that are later represented on maps to provide regular updates to everyone involved. High-resolution squares (10 meter) can be easily aggregated to lower resolution squares (1,000 meter) to represent a broader perspective for high level planning (Figure 4).
Figure 4 - Mock tornado path with 1,000m grid squares showing status of cleanup operations GIS has always included making maps; however, the tendency has been to focus on interactive, web-based, and mobile applications. While these will continue to be important, lessons learned from recent disasters, coupled with the availability of the National Grid, strengthen the need to also create high quality printed maps that are interoperable between jurisdictions at various scales to support both large and small events. After all, in an emergency situation, a map with a hole in it is still a precision instrument. A laptop with a hole in it is a paperweight.
Find additional information on the National Grid at http://www.fgdc.gov/usng .
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