GIS and GPS

GIS IS AN ACRONYM FOR

GEOGRAPHIC INFORMATION SYSTEM.

GIS refers to a computer program that manages massive sets of data from diverse sources and integrates their relationships to each other. The program displays a map of a town, a city, or a county. Layer upon layer of detailed information can be displayed on the computer map and the separate layers can be turned on or off.

There are many layers and a lot of information including: curbs, sidewalks, buildings, above ground and underground utilities, addresses, aerial photography, land survey data, demographic data, tax parcel numbers, and names of property owners.

If your are the fire chief of a town, you can go onto your computer and turn on the layer that shows the location of all fire hydrants. If you are a contractor planning to install an underground utility you can look at the GIS map with the layers showing those existing underground utilities that you will need to avoid with your excavation.

Errors in the system are not obvious to the casual user. Such programs always include a disclaimer that the information in the program should not be used to determine property boundaries. This advice is often ignored. The property map data that GIS relies upon is based on tax statements. Tax statements were never intended to define exact property ownership. The tax assessor uses abbreviated descriptions of each property and uses approximate dimensions with no regard to the science of boundary determination. Property boundaries are based upon many elements including the location of property pins and upon the legal interpretation of the description in a deed. The bottom line is that GIS data can be useful and worthwhile for a lot of reasons but like any tool it must be used with caution.  Here is a link to the USGS site which will tell you more than you want to know about GIS.

GPS IS AN ACRONYM FOR

GLOBAL POSITIONING SYSTEM