Submeter & Subfoot Accuracy

GPS (Global Positioning System) was originally developed by the United States Department of Defense as a worldwide navigation resource for military and civilian use. In 1983, President Reagan issued a directive making GPS available for civilian use shortly after Korean Air Lines Flight 007 was shot down while flying into the USSR's prohibited airspace. Since the 1980s, GPS has become widely used all over the world in electronic mapping, land surveying, scientific uses, and many others.

Today, GPS devices transmit different levels of point accuracy. Most handheld mobile computer devices that have GPS capabilities have about a two to five meter accuracy reading. However, there are some that are more accurate than others. Submeter devices can narrow down a coordinate to less than three feet. Subfoot devices are even more accurate than the submeter devices and can come within 30cm of a specified point. All of these results and measurements vary due to errors (obstructions) that will occur no matter what type of GPS you use. There are two types of corrections. Post processing is any correction made to the GPS data that is done after the GPS has collected all of the needed information. Real-time DGPS is a type of correction done while the GPS is still in use. Accuracy depends on how many satellites see the GPS signal. Satellites hover in stationary positions over the equator. Usually, there are at least six visible satellites at any given time. The biggest problem with the submeter and subfoot GPS is obstructions such as trees, buildings, etc. There are multiple signals that are sent to the device from the satellites. A poor signal will disrupt the information being transmitted.

TopCon has developed a subfoot GPS mapping system that is just as rugged as the rest of their mapping devices, but these are up to 300% more accurate than standard GPS devices. Millimeter GPS is ideal for times when high precision elevations are required.