MODERN SURVEYING INSTRUMENTS & ITS APPLICATION
MODERN SURVEYING INSTRUMENTS & ITS
APPLICATION
In conventional surveying, chain and tape are used for making linear measurements while
compass and ordinary theodolites are used for making angular measurements. Levelling work is
carried out using a Dumpy level and a levelling staff. With such surveying instruments, survey
work will be slow and tedious.
Hence modern surveying instruments are becoming more popular and they are gradually
replacing old surveying instruments such as compass and Dumpy level. With modern surveying
instruments, survey work will be precise, faster and less tedious. Some of the modern surveying
instruments are discussed in brief, in the following pages.
1. Electronic Distance Measurement (EDM) Instruments
Direct measurement of distances and their directions can be obtained by using electronic
instruments that rely on propagation, reflection and reception of either light waves or radio
waves. They may be broadly classified in to three types:
a. Infrared wave instruments.
b. Light wave instruments.
c. Micro wave instruments.
a. Infrared wave instruments
These instruments measure distances by using amplitude modulated infrared waves. At the end
of the line, prisms mounted on target are used to reflect the waves. These instruments are light
and economical and can be mounted on theodolites for angular measurements. The range of such
an instrument will be 3 km and the accuracy achieved is ± 10 mm.
Eg. DISTOMAT DI 1000 and DISTOMAT DI 5
DISTOMAT DI 1000
It is a very small, compact EDM, particularly useful in building construction and other Civil
Engineering works, where distance measurements are less than 500 m. It is an EDM that makes
the meaning tape redundant. To measure the distance, one has to simply point the instrument to
the reflector, touch a key and read the result.
b. Light wave instruments
These are the instruments which measures distances based on propagation of modulated light
waves. The accuracy of such an instrument varies from 0.5 to 5 mm / km distance and has a
range of nearly 3 km.
Eg: Geodimeter
This instrument which works based on the propagation of modulated light waves, was developed
by E. Bergestand of the Swedish Geographical Survey in collaboration with the manufacturer
M/s AGA of Swedish. The instrument is more suitable for night time observations and requires a
prism system at the end of the line for reflecting the waves.
c. Microwave instruments
These instruments make use of high frequency radio waves. Thee instruments were invented as
early as 1950 in South Africa by Dr. T.L. Wadley. The range of these instruments is up to 100
km and can be used both during day and might.
Eg. Tellurometer
Tellurometer
It is an EDM which uses high frequency radio waves (micro-waves) for measuring distances. It
is an highly portable instrument and can be worked with 12 to 24 volt battery. For measuring
distance, two Tellurometers are required, one to be stationed at each end of the line, with two
highly skilled persons, to take observations. One instrument is used as a master unit and the other
as a remote unit. Just by pressing a button a master can be converted in to remote unit and vice-
versa. A speech facility (communication facility) is provided to each operator to interact during
measurement.
Total station
It is a light weight, compact and fully integrated electronic instrument combining the capability
of an EDM and an angular measuring instrument such as wild theodolite. It can perform the
following functions.
Distance measurement
Angular measurement
Data processing
Digital display of point details
Storing data is an electronic field book
The important features of total station are,
1. Key-board-control àall the functions are controlled by operating key board.
2. Digital panel à the panel displays the values of distance, angle, height and the co-
ordinates of the observed point, where the reflector (target) is kept.
3. Remote height object à the heights of some inaccessible objects such as towers can be
read directly. The micro-processor provided in the instrument applies the correction for
earth’s curvature and mean refraction, automatically.
4. Traversing program à the co-ordinates of the reflector and the angle or bearing on the
reflector can be stored and can be recalled for next set up of instrument.
5. Setting out for distance, direction and height àwhenever a particular direction and
horizontal distance is to be entered for the purpose of locating the point on the ground
using a target, then the instrument displays the angle through which the theodolite has to
be turned and the distance by which the reflector should move.
Automatic level
An automatic level is a special surveying (levelling) instrument which contains an optical
compensator which maintains line of sight or line of collimation even though instrument is
slightly tilled.
Eg: Wild NAK2 Automatic level
Global Positioning System
This system is developed by U.S. Defense department and is called Navigational System with
Time and Ranging Global Positioning System (NAVSTAR GPS) or simply GPS. For this
purpose U.S. Air Force has stationed 24 satellites at an attitude of 20200 km above the earth’s
surface. The satellites have been positioned in such a way, at least four satellites will be visible
from any point on earth.
The user needs a GPS receiver to locate the position of any point on ground. The receive
processes the signals received from the satellite and compute the position (latitude and longitude)
and elevation of a point with reference to datum.
An Overview of GPS Surveying
Traditional surveying involves plenty of labor apart from just the expenses of conducting
the survey. The amount of money and labor involved increases with the complexity of the
terrain. If the terrain is uneven and contains bunkers, water holes, and other obstructions, it
becomes very difficult for the surveyors to collect accurate data for proper end use. These
methods are time consuming as surveyors have to make several trips to the same place for
gathering, recalculating, and double checking the data. In addition, if the weather is poor, the
surveyors have to wait until it becomes normal, further delaying the surveying process. These
problems are on the top of the priority list of federal agencies involved in surveying.
Studies conducted by the Federal Highway Administration (FHWA) over the last five years to
meet these priority shows that GPS technology can significantly increase productivity while
cutting down on costs. Several other research agencies across the US have also proved that, with
the accuracy of GPS signals, the survey can yield better results in less time. GPS surveying also
works irrespective of weather conditions. In addition, no special expertise is required to use
handheld GPS surveying instruments, which is different from the conventional machinery for
surveying.
A study conducted by the Utah Department of Transportation shows that a single person with
handheld GPS unit is almost twice as fast as the entire survey crew. The study concluded that
using GPS surveying requires fewer setups than conventional surveys. They gave an example: A
single GPS survey handheld unit recorded 5,511 topographic points in thirty working hours. The
same project using conventional survey equipment took 120 working hours to collect only 1,500
topographic points. With these results, it is very clear that a handheld GPS survey unit is the
future of surveying.
Handheld GPS Surveying Units
There are several handheld GPS surveying units on the market. To avoid confusion as to which
GPS surveying instrument to buy, first decide on the essential features you want and then go for
additional features for further enhancement of your GPS experience. While the major player in
the field of GPS surveying is Trimble, there are scores of other GPS vendors that sell handheld
GPS surveying instruments. While Garmin is also one of the leading GPS vendors, it has no
dedicated GPS surveying device. Instead, it offers some add-ons that can be used with its normal,
low-priced GPS handhelds that help with surveying.
Trimble TSC2 Data Collector
The Trimble TSC2 features a full keyboard for controlling the GPS total stations located on-site.
The piece operates on MS Windows Mobile OS facilitating sending and receiving documents on
the go. Learning is easy with the easy-to-use interface. Primarily used for measurements and
stakeout operations, this handheld GPS surveying unit can compute large data in split seconds
and helps with modeling the surface thereby allowing the surveyor to create a precise map of the
area under survey. Other features include a touchscreen, adjustable contrast with backlit LCD
screen, 512 MB memory, 516 MHz processor, integrated WiFi, and Bluetooth for quick access to
the Internet and local networks.
Garmin GB Discoverer
The Garmin GB Discoverer is basically an extension that is compatible with most of Garmin's
GPS handhelds. Once you select any basic GPS handheld with navigation features (such as
Dakota 20 and Oregon), you can get the Garmin GB Discoverer to help you with surveying, too.
The module is a joint effort of Garmin and Ordnance Survey mapping that produces precise
topographic maps in both raster and vector maps. All you need to do is to download the Garmin
GB Discoverer to your GPS navigation handheld, preferably one from the Dakota series, to get
unlimited maps of any area covering the entire UK.
In short, this means that Garmin offers you surveying as an additional capability to your existing
GPS handheld, thereby avoiding the need to purchase a specific GPS survey handheld. You can
use all the features of the Garmin GPS handheld such as the Lane Assistant or Golf GPS along
with surveying facility.
Besides, you can spend some time on the Internet to study the different models and makes of
handheld GPS survey unit available for sale, both new and used, thus saving on the costs.
Use of GPS in Construction Surveying – Feasibility of GPS Surveying Instruments
GPS surveying instruments offer measurements in 3D (X, Y, and Z planes) that make it
easy for the surveyor to take precise measurements for any point of the area. The GPS surveying
instruments receive signals from GPS satellites in terms of longitude, latitude, and elevation (from
sea level) along with some other information that helps the GPS surveying instrument display
exact measurements.
It hardly takes around 5 minutes at each point in the area being surveyed to gather all data from
satellites and display results. Unlike traditional surveying, measurements can be taken by a
single person holding the GPS surveying instrument for a few minutes at the different points on
the area to collect the measurements that are computed by the GPS surveying instrument based
on radio signals from the GPS.
With the GPS surveying instrument in his hand, the construction surveyor can take precise
measurements without the requirement of line of sight. These devices work under any weather
conditions. Thus, the process of construction surveying became very easy, fast, and above all,
more precise with the use of GPS surveying instruments.
The only problems with the GPS surveying instruments are that there should be no obstructions
nearby so that the GPS receiver can easily receive the GNSS signals. For better measurements
and more accuracy of GPS data, it is recommended that the surveyor does not use the handheld
GPS surveying instruments near high buildings or under trees. The other problem is learning to
use the GPS device. The ease of learning depends upon the type of the GPS surveying
instrument. Some devices offer easy menus while others are feature rich thereby having a
complex menu.
With so many benefits, the GPS surveying instruments are necessary for people into construction
surveying they take out the stress out of the work, making it enjoyable.
There are even GPS handhelds for construction surveying. The following section reviews three
of the most used GPS surveying instruments.
GPS Survey – An Introduction
The term "Survey" has different meanings in different contexts. It may refer to the study
of opinions of people about any item or service or may refer to "Census," too. Though there are
different types of surveys, the term is most commonly used to refer to measuring a portion of
land so as to present data relevant to the area. This data is then used for different end uses, such
as constructing a building. There may be several objectives of land surveying. The person who
conducts survey of a particular area is called a surveyor and has to undergo training to
understand how to survey any piece of land.
Normally, a survey involves several people who use mechanical and electromechanical
equipment that help them in measuring and collecting data about any piece of land. This
equipment may include a compass, measuring tapes, calculators, and much more. The precision of
data in a survey depends on the area of the land under survey. Line of sight also plays an
important role in traditional surveys as most of the measurements are manually done.
Most of the difficulties, costs, and errors are eliminated when surveyors use GPS in surveys.
(The linked article describes how GPS plays a role in determining and mapping terrain.) With the
easy availability of GPS handhelds, surveyors now use GPS survey equipment, which eliminates
the need for several people while also replacing the traditional equipment that often produce
erroneous results if not maintained properly. For example, before using a compass in a land
survey, you need to make sure that the needle is not subject to friction. If it is, then it won't be
showing the right direction!
Surveyors need not wait for good weather when they are employing GPS in survey as "line of
sight" has no role when the survey is dependent on GPS. Data is obtained directly from satellites
and the GPS survey equipment does the necessary computation reducing error possibilities to
minimum.
Depending upon the objective of GPS survey, a surveyor can select from the different types of
GPS survey equipment available. Normally, the GPS survey equipment are the same as any
other GPS handheld except that they should certain features pertaining to surveying, such as
obtaining signals from 2 or more satellites at a time. The next page offers a glance at things to
consider when condsidering GPS survey equipment.
Application of GIS in Geological Mapping – Fast, Accurate, and Cost-Effective
Geological features are dependent on space and time. The Geographical Information
Systems (GIS) are capable of defining all three factors of space (represented by the X, Y, and Z
planes) and time. The signals from the satellites allow the GIS to read information in term of
longitude, latitude, and elevation (compared to the sea level). This information helps in
determining all three planes that guide GIS tools in creating a 3-D image of the area under
survey.
The satellite signals also send in information about the time when the satellite released the
signals, clock redundancy of the transmitters in the satellites, and coefficient of error through the
speed of signal in the space as well as in the different layers of atmosphere. Based on these four
factors, surveyors can create accurate geological maps of the area under survey.
Though the old methods of geological methods (based on multivariate statistics) are still in use in
some countries, the GIS is the most preferred as it is cost-effective and offers more accurate data,
thereby easing the scaling process when studying geological maps.
GIS helps in scanning, referencing, and reproducing older maps at any desired scale. Using GIS,
several archeological geological maps (having different scales) have been combined into a single
map (with single scaling) with even more accuracy, thus saving the time of scientists, engineers,
and researchers who need to study the area.
Using the accurate scaling obtained from GIS, different projects can be planned without
the need of additional equipments for surveying the area. The different projects that can be
planned and implemented using applications of GIS in geological mapping can be anything from
creating a dam or reservoir to roads, highways and railroads to an entire town. The benefits of
application of GIS in geological mapping are visible when different projects can be entirely
planned without even leaving the conference room!
THE MAJOR BENEFITS OF ELECTRONIC SURVEYING EQUIPMENT
Today electronic surveying gear has changed into a major tool in the construction
industry. It is thru the employment of such clobber a surveyor can much easier define particular
dimensions to guarantee the building work being carried out is done so in the correct way.
Though surveying has been about for many centuries now ( both the Egyptians and Romans were
using it to build their roads and buildings ( pyramids included ) it's actually extremely
complicated to figure out just when it was first used.
All of the parts that is used today will be compromised of 3 different parts which can measure
distance, angles as well as the elevation of an item. But the fantastic thing about all surveying
apparatus including electronic versions is they may be able to measure a few of the parts we have
discussed formerly. However because there are that many different items of equipment to choose
between it may become rather overwhelming when somebody has to make a choice on just
which one they should use, particularly if an individual has limited or no experience of
surveying.
Below we however provide details of some of the categories of surveying apparatus that are now
in use today. Electronic Levels These transmit a beam of infrared light which is not visible to the
bare eye and helps to create a point or known reference elevation and is employed so as to take
measurements during construction works. There are 2 different sorts of electronic level which
many surveyors are using either the single beam or the revolving beam. The single beam projects
a light which can either be projected to another point either vertically, horizontally or at an
incline.
While the revolving beam supplies the surveyor with an aircraft of reference covering a specific
open area. All these varieties of levels are self levelling and won't start working until the
instrument has levelled itself in the correct way. Plus if at any point if the level being moved or
knocked the light is immediately turned off and will only come back on once the clobber has
levelled itself. Two. Electronic Distance Measurers Regularly more ordinarily called EDMs and
are used to meticulously measure the gap between one point and another. This piece of electronic
surveying apparatus works by measuring how long it takes the laser to go from the EDM to a
prism placed at a different location and then back to the EDM again.
However before the discovery of this piece of electronic hardware tapes or chains were used so
as to provide correct measurements of the gap between 2 points. As with all modern electronic
surveying hardware they are going to use a computerized system which is ready to collect and
record all of the info picked up out on site before it can be transferred over to a P. C. and the info
printed. This so makes the job of the surveyor way easier to do and will supply them with correct
readings and measurements at every point.
THE ADVANTAGES OF USING ELECTRONIC SURVEYING EQUIPMENT
Today electronic surveying gear has changed into a major tool in the construction
industry. It is thru the employment of such clobber a surveyor can much easier define particular
dimensions to guarantee the building work being carried out is done so in the correct way.
Though surveying has been about for many centuries now ( both the Egyptians and Romans were
using it to build their roads and buildings ( pyramids included ) it's actually extremely
complicated to figure out just when it was first used.
All the gear that is used today will be compromised of 3 different elements which can measure
distance, angles as well as the elevation of an item. But the nice thing about all surveying
apparatus including electronic versions is they may be able to measure one or two of the
elements we have discussed formerly. However because there are that many different pieces of
kit to make a choice from it may become moderately overpowering when an individual is having
to make a call on just which one they should use, especially if an individual has limited or no
experience of surveying.
Below we however provide details of some of the categories of surveying apparatus that are now
in use today. Electronic Levels These transmit a beam of infrared light which is not visible to the
bare eye and helps to create a point or known reference elevation and is employed so as to take
measurements during construction works. There are 2 different sorts of electronic level which
many surveyors are using either the single beam or the revolving beam. The single beam projects
a light which can either be projected to another point either vertically, horizontally or at an
incline.
While the revolving beam supplies the surveyor with an aircraft of reference covering a specific
open area. All these sorts of levels are self levelling and won't start working till the instrument
has levelled itself in the correct way. And if at any time should the level being moved or knocked
the light is instantly turned off and will only come back on once the kit has levelled itself. Two.
Electronic Distance Measurers Regularly more commonly called EDMs and are used to exactly
measure the gap between one point and another. This actual piece of electronic surveying kit
works by measuring how long it takes the laser to go from the EDM to a prism placed at a
different location and then back to the EDM again.
However before the discovery of this piece of electronic kit tapes or chains were used so as to
provide correct measurements of the gap between two points. As with all modern electronic
surveying hardware they're going to use a computerized system which is able to collect and
record all of the info picked up out on site before it can be transferred over to a PC and the info
printed. This so makes the job of the surveyor far easier to execute and will supply them with
correct readings and measurements at all times.