One of the most significant technology that have increased the efficiency and accuracy of surveying is GPS or Global Positioning System. GPS is basically a constellation of 24 Navstar satellites which orbits the Earth at 11,000 Km. The GPS Survey is based on the principle of the satellite ranging i.e it determines the position of any particular location of the earth in respect to the distance of that particular position from the satellites.
Surveying by GPS involves the determination of three elements:
- X cordinate i.e. the longitude
- Y cordinate i.e. the latitude
- Z cordinate i.e. the height or altitude of a place above the Mean Sea Level.
Principles of GPS Survey:
- The basis of the survey is the ‘triangulation’.
- This triangulation is mainly done by the calculating the travel time of the radio signals.
- The GPS should be provided with an accurate clock to measure the signal travel time.
- Finally logical error correction should be done for any delays due to the disturbances created by the atmosphere.
GPS Survey System & Its Working:
The GPS Survey system can be divided into three segments:
- The Space Segment : this consists of the satellites which continuously orbits round the planet Earth.
- The Control Segment : This consists of the 5 monitoring stations around the Earth which controls the various aspect of the satellites like transmission of data to the satellite, serving as the uplink installations, clock correction and message broadcasting. The five control stations are:
i) Colorado Springs
ii) Ascesion Island
iii) Diego Garcia
iv) Hawaii
v) Kwajalein Island
- The User Segment: This constitutes a GPS receiver which consists of an antenna, preamplifier, radio signal microprocessor, control & display device, data recording unit, and power supply. The receiver works by decoding the timing signals from the satellites (at least four) and determine their distances, latitude, longitude, elevation, and time.
However, with the advancing time GPS has also undergone a massive change featured by the enhancement of accuracy and precision. Differential GPS or DGPS is characterized by the presence of two receiver at the field at the same time. one of them should be placed in a known position (base station). The known location collect the data in the base station format. The other station also collect the data in the same format. Then differential processing is done to find the position of the unknown location in respect to the base station. This lead to the minimization of the error.
Advantages of GPS Surveying:
GPS Survey enjoys certain advantages for which its is very popular with most of the developed nations. The advantages of GPS Surveying are:
- It is fast, accurate and precise in working.
- It doesn’t involve the troublesome ground to ground survey by conventional instruments.
Use of GPS Survey:
GPS Survey has given the art of Mapping a new dimension. Mapping was never so easy, fast and accurate. It is used to make road maps and environmental hazards like landslides, forest fires, and oil spills. Cadastral mapping and topographical mapping through GPS Survey needs a high degree of accuracy and carried out by improved receivers. It also plays an indispensable role in generation of the spatial data for the Geographical Information System (GIS) and Remote Sensing (RS).
So, all you need a set of GPS receiver to know your planet better. Explore it out with the latest technology called GPS .
Map Digitization