SURVEYING USING TOTAL STATION

 A total station is a combination electronic theodolite and electronic distance measuring device (EDM).  With this device, one may determine angles and distances from the instrument to points to be surveyed.  With the aid of trigonometry, the angles and distances may be used to calculate the co-ordinates (x, y, and z or northing, easting and elevation) of surveyed points in absolute terms.

 To calculate co-ordinates, the measured angular and linear data is transferred to a microprocessor in the total station.  Using the inbuilt programmes of the microprocessor according to the programme chosen by the operator the results will be displayed on the screen.  The co-ordinate data can be saved in the internal or external memory of the total station instrument.

Total station only measures three parameters: Horizontal angle, vertical angle and slope distance Angle measurement Most modern total station instruments measure angles by means of electro-optical scanning of extremely precise digital bar-codes etched on rotating glass cylinders or discs within the instrument. The best quality total stations are capable of measuring angles to 0.5 arc second.

Distance measurement When a distance is measured with a total station, an electromagnetic wave or pulse is used for the measurement – this is propagated through the atmosphere from the instrument to reflector or target and back during the measurement. The modulation pattern in the returning signal is read and interpreted by the computer in the total station. Most total stations use purpose-built glass corner cube prism reflectors for the EDM signal. A typical total station can measure distances with an accuracy of about parts per million over a distance of up to 1,500 meters (4,900 ft

HORIZONTAL ANGLE The horizontal angle is measured from zero direction on the horizontal scale. VERTICAL ANGLE The vertical angle ( Zenith angle) is measured relative to the local vertical direction Zenith angle 0 – vertical up 90 – horizontal 180 – vertical down

Basic calculations θv – vertical angle θh – horizontal angle S – slope distance θvθv S sin θ v S cos θ v S Horizontal distance = S sin θv Vertical distance = S cos θv

S sin θ v Cos θ h S Sin θ v Sin θ h S Sin θ v θhθh

ADVANTAGES OF TOTAL STATION SURVEYING Accurately gathers enormous amount of survey measurements quickly Receiving and transmitting measured or layout data increases processing efficiency Read and write errors are eliminated Data is saved and managed on a PC Designs can be implemented from planning stage Overall reduction in man hours spend on the job

DISADVANTAGES OF TOTAL STATION SURVEYING  No hard copies : difficult to look over And check the work  Instrument is costly and skilled personal is required

REMOTE SENSING

What is remote sensing? The science (and art) of acquiring information about an object, without entering in contact with it, by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.

BASIC PRINCIPLE OF REMOTE SENSING Remote sensing is done with the help of mechanical device called remote sensors These sensors are positioned away from object of interest by using helicopters, planes, satellites. Most sensing devices record information about an object by measuring an object’s transmission of electromagnetic energy from reflecting surfaces The simple form of remote sensing uses photographic cameras to record information from visible or near infrared wavelengths.

Using remote Sensing, We can measure: Temperature Soil moisture Mineral and rock types Rainfall Snow cover, snow depth or snow water equivalent Vegetation type and biomass Sea ice properties (concentration, thickness, extent, area) Elevation and change Aerosol, gas types and concentration

Agricultural Efficiency Air Quality Water Management Disaster Management Carbon Management Aviation Ecological Forecasting Invasive Species Coastal Management Homeland Security Energy Management Public Health Applications of National Priority

INFORMATION ABOUT AN OBJECT OR AREA Sensors can be used to obtain specific information about an object (e.g., the diameter of a cottonwood tree crown) or the geographic extent of a phenomenon (e.g., the boundary of a cottonwood stand). The EMR reflected, emitted, or back -scattered from an object or geographic area is used for the actual property under investigation. The electromagnetic energy measurements must be calibrated and turned into information using visual and/or digital image processing techniques.

GPS & GIS – Introduction

Global Positioning System (GPS) The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S.Department of Defense. GPS satellites 24 Satellites in 6 planes, each plane has 4 satellites These space vehicles (SVs) send radio signals from space.

What is GPS? GPS stands for Global Positioning System GPS is a satellite navigation system designed to provide accurate position, velocity, and time information almost anywhere in the world the present system is known as NAVSTAR - NAVigation Satellite Timing And Ranging the GPS program operated and controlled by the US Department of Defense

How does GPS work? Each satellite broadcasts its orbital position as a modulated signal Receiver determines the difference between the time signal from the satellite and its own internal clock The distance from the satellite can be calculated using the speed of light (300,000 km/second) Position and distance from 3 or 4 satellites allows triangulation of receiver’s position

What does the GPS do Satellite signals can be processed in a GPS receiver. GPS receiver will show your EXACT location on the Earth (latitude and longitude) Helps you find your way to a specified location Let’s you know what direction you are heading and how fast you are going

Major GPS Components

Space Segment All operational satellites

Control Segment There are five Control Stations around the world All ground stations involved in the monitoring of the system – Master Control Stations, Monitor stations and Ground control stations

User Segment All civilian and military users

APPLICATION OF GPS Location Navigation Tracking Mapping Timing

Geographic Information Systems - GIS GIS is a spatial database with a strong visual display component GIS is specialized computer programms designed to analyze spatially referenced data GIS integrates hardware, software and data for capturing, managing, analyzing and displaying all forms of geographically referenced information

COMPONENTS OF GIS Hardware : Computer system on which GIS operates Software : provide functions and tools need to store, analyse, and display geographic information Data : Most important component of GIS. In two forms Geographic data or spatial data Attribute data People: Methods

GIS FUNCTIONS Capture Store Query Analyse Display Output

GIS based on many disciplines and technologies – Geography – Computer science – Mathematics – Statistics – Remote sensing/GPS/surveying – Telecommunications/Internet – Operations research/information science