3M Dynatel M-Series - Manual (Page 3)

What is GPS?
The Global Positioning System (GPS) is a worldwide radio-navigation system
formed from a constellation of 24 satellites and their ground stations. A GPS
receiver uses these satellites as reference points to calculate positions
accurately.
How does GPS Work?
The basis of GPS is "triangulation" from satellites. To "triangulate," a GPS
receiver measures distance using the travel time of radio signals. To measure
travel time, GPS needs very accurate timing. Along with distance, you need to
know exactly where the satellites are in space. High orbits and careful monitoring
are the key. Finally you must correct for any delays the signal experiences as it
travels through the atmosphere.
Mapping with GPS
Historically, utility company maps have been mostly schematic in nature. Hand
drawn maps were often based on sketches completed by engineers or
installation crews. They portrayed the components of the system but their
positioning was not accurate enough. The on-map relationships of key
components such as valves, transformers, and regulators were approximate.
Global positioning system (GPS) technology allows utility companies to increase
the accuracy of their electronic maps to provide more effective facility
management, planning and design.
GPS Technology
Some GPS devices fall into the general class of GPS receivers referred to as
"sub-meter" or "mapping grade." They are capable of a final resolution of
positions within a meter (approx. 40 inches) of their true locations. Note that the
total error will be twice that number between two measurement times.
Furthermore, the worst-case accuracy depends on many factors such as:
number of satellites in view, the position of the satellites, atmospheric conditions,
foliage, buildings etc.
Mapping of 3M™ Electronic Markers
3M™ Dynatel™ M-series Marker Locators can be configured to send iD marker
data directly to some GPS devices. When a marker is located and read, feature
and attribute data is sent to the GPS device and is stamped with latitude,
longitude and date/time data. The data acquired during this logging process can
be uploaded to mapping software, and your markers with all the data read from
them, are on the map!
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