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.