2. Content
-Introduction
-Electromagnetic wave
-Properties of Electromagnetic Waves
-Principle of EDM
-Types of EDM Instruments
-Total Station
-Types of Total Station
-Measuring Angle
-Advantages and Disadvantages
-Digitals self and Levelling level
3.
4. MODERN SURVEYING EQUIPMENT
Revolutionary changes have taken place in last few
years in surveying instruments that are used for
measuring level differences, distances and angles.
This has become possible because of introduction of
electronics in these measurements. With rapid
advancements in the technology and availability of
cheaper and innovative electronic components, these
instruments have become affordable and easy to use.
6. Electromagnetic waves
The EDM method is based on generation, propagation,
reflection and subsequent reception of electromagnetic
waves
The distance is measured indirectly using the
characteristics of these waves
The electromagnetic waves required no medium and they
can travel even in vacuum
7. Properties of electromagnetic wave
Cycle : when the wave moves through two identical point
on its path it is said to have completed one cycle.
Wave length : the distance two identical points on a wave
is called wave length.
Frequency : frequency refers to the number of cycles of
wave passing a fixed point per unit time it is denoted by
the Greek letter nu.
8. PRINCIPLE OF EDM
The general principle involves sending a modulated Electro-
magnetic (EM) beam from one transmitter at the master station
to a reflector at the remote station and receiving it back at the
master station.
The instrument measures slope distance between transmitter
and receiver by modulating the continuous carrier wave at
different frequencies, and then measuring the phase difference
at the master station between the outgoing and the incoming
signals. This establishes the following relationship for a double
distance (2D)
10. Micro Wave Instruments
These instruments make use of micro
waves.
Tellurometers come under this
category.
Tellurometers can be used in day as
well as in night.
The range of these instruments is up to
100 km.
11. Infrared Wave Instruments
In this instrument amplitude modulated infrared waves
are used.
Prism reflectors are used at the end of line to be
measured.
These instruments are light and economical and can be
mounted on theodolite.
With these instruments accuracy achieved is ± 10 mm.
The range of these instruments is up to 3 km.
12. Light Wave Instruments
These instruments rely on propagation of modulated light
waves.
During night its range is up to 2.5 km while in day its
range is up to 3 km.
Accuracy of these instruments varies from 0.5 mm to 5
mm/km distance.
16. TOTAL STATION
These instruments can record horizontal and vertical angles
together with slope distance and can be considered as combined
EDM plus electronic theodolite.
The microprocessor in TS can perform various mathematical
operations such as averaging, multiple angle and distance
measurements, horizontal and vertical distances, X, Y, Z
coordinates, distance between observed points and corrections for
atmospheric and instrumental corrections.
17. Advantages of total station
Area of the field can be computed.
Automation of old maps.
Graphical view of plots and land for quick visualization.
Local language support.
Full GIS creation using map info software.
The instruments can be easily set on tripod using laser
plumber.
18. Disadvantages of total station
For on overall check of the survey, it will be necessary to return
to the office and prepare the drawing using appropriate
software.
The instrument is costly.
Skilled personnel are required for conducting surveys.
19. Measuring angles
For measuring angles optoelectronically, the absolute
circle scanning system used to read the coded graduations
of a glass circle.
The circle contains only one coded graduation track which
contains all the information's.
The code is read by linear CCD array and an analogue to
digital converter and displays with maximum accuracy.
20. Types of total stations
Manual total stations
Semi-automatic total stations
Automatic total stations
21. Manual total stations
In this type of total stations it was necessary to read the
horizontal and vertical angles manually.
Only slope distance could be read electronically.
22. Semi-automatic total station
For these instruments the user had to manually read the
horizontal circle.
Vertical circle reading were shown digitally.
Slope distances with their horizontal and vertical
components are displayed digitally.
23. Automatic total stations
This type is the most common total station used now-a-
days.
They sense both horizontal and vertical angle
electronically.
The coordinate information obtained can either be stored
in the total stations memory card.
24. DIGITAL LEVEL
Recently electronic digital levels have evolved as a result of
development in electronics and digital image processing.
Digital levels use electronic image processing to evaluate the
special bar-coded staff reading.
This bar-coded pattern is converted into elevation and distance
values using a digital image matching procedure within the
instrument.
25. Various capabilities of digital levels are as follows:
1. measuring elevation.
2. measuring height difference.
3. measuring height difference with multiple instrument
positions.
4. levelling
6. setting out with horizontal distance
7. levelling of ceilings
