Javad Maxor, User Manual

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www.javad.com Maxor User’s Manual 1-3
I N T R O D U C T I O N
Principles of Operation
Principles of Operation
Surveying with the right GPS receiver can provide users accurate and precise
positioning, a requirement for any surveying project.
This section gives an overview of GPS and receiver functions to help you
understand and apply GPS principles, allowing you to get the most out of your
receiver.
GPS Overview
The Global Positioning System (GPS) is a satellite-based, line-of-sight radio
navigation system run by the United States Department of Defense (DoD). This
system offers a global, all weather, 24-hour positioning, velocity, and time
service to any user equipped with a GPS tracking receiver, who is on or near the
Earth’s surface. The Global Navigation Satellite System (GLONASS), is the
Russian Federation Ministry of Defense counterpart to GPS. At any one time,
with a standard 15 degree angle, up to 10 or 12 GPS satellites are visible from
any point on earth. When a receiver can also track GLONASS satellites,
between 10 and 16 satellites are visible.
For information on the current status of the GPS constellation, visit
http://tycho.usno.navy.mil/ or http://www.navcen.uscg.gov/. For GLONASS,
visit http://www.glonass-center.ru/frame.html.
Despite numerous technical differences in the implementation of these systems,
both GPS and GLONASS have three essential components:
• Space – GPS and GLONASS satellites orbiting approximately 12,000
nautical miles above Earth and are equipped with a clock and radio. These
satellites broadcast digital information (ephemerides, almanacs, time
frequency corrections, etc.).
• Control – Ground stations located around the Earth that monitor the satellites
and upload data, including clock corrections and new ephemerides (satellite
positions as a function of time), to ensure the satellites transmit data properly.
• User – The community and military that use GPS/GLONASS receivers and
the corresponding satellites to calculate positions.