Global Positioning System { GPS } in Surveying

Importance of Global Positioning System (GPS) in Civil Engineering

Global Positioning System is a system developed by the US Department Of Defence (D.O.D) for military as well as Civil operations. The D.O.D sustains it. The Global Positioning System provides quickly, accurate and inexpensively to determine the time, position and velocity of any object on the globe at any time with the help of signals from satellites put in earth centered orbits.

The NAVSTAR Global Positioning System is a satellite based radio positioning and lime-transfer system designed, financed, deployed, and operated by the department of U.S Department of Defence.

Global Positioning System has also demonstrated a significant benefit to the civilian community  who are applying GPS to a rapidly expanding number of applications.

The Major Attractions of Global Positioning System

  • The relatively high positioning accuracy from tens of metres down to the millimetre level.
  • The capability of determining velocity and time to an accuracy commensurate with position.
  • The signals are available to users anywhere on the globe in the air, on the around, or at sea.
  • It is a positioning system with no user charges, that simply requires the use of relatively low cost hardware.
  • It is an all-weather system, available 24 hours a day.
  • The position information is in three dimensions, that is vertical as well as horizontal information is provided.
  • It is suitable for all classes of platform : aircraft (jet to helicopter), ship, land (vehicle-mounted to handheld) and space (missiles and satellites).
  • Able to handle wide variety of dynamics.
  • Real time positioning, velocity and time determination capability to an appropriate accuracy.
  • The positioning results were to be available on a single global geodetic datum.
  • Highest accuracy to be restricted to a certain class of user.
  • Resistant to jamming (intentional and unintentional).
  • Redundancy provisions to ensure the serviceability of the system.
  • Passive positioning system that does not require the transmission of signals from the user to the satellites.
  • Able to provide the service to an unlimited number of users.
  • Low cost, low power, therefore as much complexity as possible should be built into the satellite segment.
  • Total replacement of the transit satellite and other terrestrial navaid systems.

Applications and Uses of Global Positioning System :

  • Land, Sea and Air Navigation and Tracking including onroute as well as precise navigation, collision avoidance, cargo monitoring, vehicle trucking, search and rescue operations, etc.
  • Surveying and Mapping on land, at sea and from the air includes geophysical and resource surveys, GIS data capture surveys, etc.
  • Military Applications : Although these are largely mirrored by civilian applications, the military Global Positioning System are generally developed to military specifications and a greater emphasis is placed on system reliability.
  • Recreational uses on land at sea and in the air.
  • Other specialized uses such as time transfer, attitude determination, spacecraft operations, atmospheric studies etc.
  • Most useful in marine and air navigation, transport management and several kinds of automation.
  • Easy collection of data on specified profile and cross sections.
  • Plotting of contours from collected data.
  • Local property mapping and locating boundaries.
  • Site surveys.
  • Topographic surveys etc.
  • Determining coordinates of photocenters in aerial mapping, layout works etc.
  • Exploration of mineral wealth.

Advantage of Global Positioning System (GPS)

  • Using geodetic receivers, point positioning to an accuracy of 1 cm can be displayed by the user equipment.
  • GPS Survey can be carried out in any kind of weather – rain, fog or poor visibility without any hindrance during day or night.
  • There is no need for intervisibility of stations or points surveyed and hence control stations can be located advantageously.
  • Global Positioning System together with Geographical Information System is a dynamic and spatially related information capable of processing and routing and weapons aiming.

Disadvantages of GPS :

  • High cost of GPS survey comes in the way of realizing the full potential of this surveying.
  • Difficulties in defining datum heights with reference to mean sea levels and real time data processing and control are also part of the process.

Leave a Reply