WHAT IS GIS & GPS?

Geographic Information Systems
A geographic information system (GIS) is a computer-based system used to combine layers of geographic information about an area (maps), with data about an area, in order to produce analysis of the area. For example, in a GIS, a user could combine layers of building footprints and factories to see which buildings could be in danger if there was a chemical leak at the factory. While the GIS can easily show which buildings would fall into a certain radius of the factory, it could also tell you the names of the people living in the buildings, the average household income of the houses affected, and much more. (more info...)

At the Southside Planning Commission, we use GIS in a variety of ways. Some of them follow:

Economic Development: We produce many maps that are included in promotional material, given to industrial prospects. These maps often are tailored to fit the industry, and to highlight the advantages of locating in Lake Country.

Census Data: we can combine Census data with TIGER 2000 Census Blocks to find the population living in a certain radius of a point, in a town or county, or as a buffer along a highway. We have used the Census data in the past to show areas of high growth in the county, or to point out racial makeups of an area. Census data was used in Halifax County to create new magisterial districts, where each had to have a certain percentage of minorities.

Local Government Assistance: Our GIS program is put to use often as assitance to county or town governments. Sometimes these are simple road maps of a neighborhood. Other times the project may be as complex as using GPS technology to map out water or sewer infrastructure in a town, align that data with other paper maps or aerial photographs, and produce maps for the town. Many times these projects would be much more costly for the town or county to contract out, yet well within our capabilities here.

Transportation and Recreation: Our GIS has been used to map out new nature trails and historic driving tours. With the information we have, we can figure out the best way to route the tour or trail to better utilize the surrounding environment. One project currently in the works, is an equestrian / biking trail in Halifax County. Using aerial photos, transportation layers, and hydrology (water) layers, we were able to map out the trail as it runs up the side of the Roanoke River.

Residential Building Permits: Since 1999, we have been combining information about residential building permits with their geographic location. In addition to locating where the building is, we track the estimated value of the project, the type of construction, occupancy type, and square footage. With this information linked in the GIS, we can show which areas of the district are experiencing growth in terms of housing.

Global Positioning Systems (GPS)
GPS is a satellite-based navigation system that is made up of a network of 24 satellites orbiting Earth. The system was built by the Department of Defense for military purposes, but was later made available for civilian use. Using a GPS-enabled device, one can pinpoint their location in latitude and longitude in a matter of seconds. GPS is used by hikers to stay on their intended path, and by airplane pilots to ensure that they are headed in the right direction to get to their destination. Many vehicles are now coming equipped with a GPS built into the dashboard, for navigating to destinations such as the shopping mall or a vacation spot. (more info...)

We use GPS along with GIS for mapping purposes. Using a handheld data collector, and a GPS receiver, we can go out into the field and take a GPS position. The position is stored in the handheld computer, and any data that we want to store with it (feature name, condition, description, etc.). Once we have all the positions that we need, we can come back to the office, download the information into a GIS program, and overlay the locations taken with GPS on top of other map layers. This way, we can build an accurate database of anything from water valves to road centerlines.

The GPS we use is the Trimble Pathfinder Pro XRS. It is a mapping-grade GPS capable of taking positions that are within a meter of their actual location on the Earth's surface. (Most consumer level GPS's have accuracy of about 20 feet or more.) The system is used in the field to log the positions, and add any extra data that is needed. Then, the data logger is connected to the computer, where we can download the positions that were recorded by the GPS, into the GIS software to use in mapping.