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SURVEYING
Surveying is the art of determining the relative positions of points on, above or beneath the
surfaceoftheearthbymeansofdirectorindirectmeasurementsofdistance, direction and elevation.
Objectives of surveying
* To measure the Horizontal distance between the points
* To measure the vertical elevation between the points
* To find out the relative direction of lines by measuring horizontal angles with reference to any
arbitrary direction
* To find out the absolute direction by measuring horizontal angles with reference to a fixed
direction
Primary divisions of survey
• plane surveying
• Geodetic surveying
Plane surveying:
Type of surveying in which the mean surface of the earth is considered plane and the spheroidal
shape of the earth is neglected
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* The survey extended to small area<200km
* Plane survey is used for layout of canal ,building,highways,railways etc
Geodetic survey:
Shape of the earth is considered
* area>200 km2
Classification of surveys
A)
Based on nature of the field survey
a) land surveying:
* Topographical survey:
* Horizontal and vertical location of certain points by linear and angular measurements and is
made to determine the natural features of a country such as rivers, streams, lakes, woods, hills
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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etc and artificial features as roads ,railways, canals etc
* Cadastral survey: are made incident to fixing the property lines
* City survey: made in connection with the construction of streets, water supply
system, sewers etc
b) Marine or hydrographic survey:
* Deals with the bodies of water for purpose of navigation, water supply, for the
determination of mean sea level
c) Astronomical survey:
* This consist in observation to the heavenly bodies such as the sun or any fixed star
B) Based on the object of survey
1) Engineering survey: undertaken for the determination of quantities or to afford
sufficient data for the designing of Engg works such as roads and reservoir
2) Military survey: used for determining points of strategic importance
3) Mine survey: used for exploring mineral wealth
4) Geological survey: used for determining different strata in the earth's crust
C. classification based on instruments used
1) Chain survey
2) Theodolite survey
3) Traverse survey
4) Triangulation survey
5) Tacheometric survey
6) Plane table survey
7) Photogrametric survey
8) Aerial survey
Principles of surveying
Under the following two aspects
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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1) Location of a point by measurements from two points of reference
2) Working from whole to part
1) Location of a point by measurements from two points of reference
The relative position of points to be surveyed should be located by measurements from at least two
points of reference, the position of which have already been fixed
2) Working from whole to part
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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According to this principle, it is always desirable to carryout survey work from whole to part.
This means, when an areas is to be measured, first a system of control points is or established
covering the whole area with very high precision. The minor details are located by less precise
methods
LINEARMEASUREMENTS
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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TAPES
Tapes are used for more accurate measurements and are classed according to the material of which
they are made,
1) Cloth or linen tape
2) Metallic tape
3) Steel tape
4) Invar tap
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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Cloth or linentape:
* Closely woven linen
* 12to15 mm wide vanished to resist moisture, are light and flexible
* Commonly available length10m,20,25,and30 meters,and in33ft, 50ft ,66ft,100ft
* The end of the tape is provided with small brass rings whose length is included in the total length
Draw backs;
Easily affected by moisture,
Length altered by stretching, likely to twist and tangle, not strong
Metallic tap
* A linen tape reinforced with brass or copper wire to prevent stretching of fibers
* Made up of varnished strip of waterproof linen inter woven with small brass
* Not easily strecheable
* Made in length of 2,5,10,20,30and 50meters and width 16mm
* Used for taking offset distance in chain survey
Steel tape

Consist of light strip of steel with width 6to10mm
* Available in length of 1,2,10,20 and30 meters
* Marked with meters, decimeter and centimeters
* Used for testing chain length and measurements of buildings
InvarTape
* mainly for linear measurements of very high precision
* Invar is an alloy of steel (64%)and nickel(36%)
* Low coefficient of thermal expansion
* Error due to temperature fluctuations is low
* More expensive
* Much softer and more easily deformed than steel
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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Ranging
When a survey line longer than the chain length, it is necessary to align intermediate points on
chain lines so that the measurements are along the line. The process of locating intermediate points
on survey line is known as ranging
There are two methods of ranging:
1. Direct ranging
2. Indirect ranging
Direct ranging:
The process of establishing intermediate ranging rod along the chain line by direct observation
from either end station is known as direct ranging. Done when the two ends of the survey line are
intervisible,
The figure shows the two intervisible points A and B in which an intermediate station C is to be
located .Point C Should be selected at a distances lightly less than a chain length . At points A and
B ranging rods are fixed . The assistant hold another ranging rod near C. The surveyor stands about
2 meters behind the station A and looking along the line AB direct the assistant to move at right
angles to the line AB till he aligns the ranging rods along AB.
The surveyor instructs the assistants to mark that point and stretch the chain along AC.
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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Instrumentsusedforranging
Fieldbook
The book in which the chain or tap measurements are entered is called the fieldbook . It is an
oblong book of size 20x12cm and open length wise. The main requirements of field book are that it
should contain good quality stout opaque paper. It should be well bound and of size convenient for
the pocket. There are two forms of field book.
1. Single line field book
2. Double line field book
Single line field book
* Survey line or chain line represented by a single red line marked at the center of the page
* Used for comparatively large scale and most detailed dimension work
* Written the distance along the chain line
Double line field book
* Consists of two line either red or blue color marked at the center of the page
* Two lines spaced about1.5to2 cm apart
* Used for ordinary work
* Entering Chainages between these lines
Following details must be given:
* Date of survey and names of surveyors,
* Name of stations
* Details of survey line,
denotes the starting station and
Denotes the end station.
Name of satiation to be entered close to the this symbol
* All distance along the chain line are entered in central column
* Al lobjects offered right or left of chainl ines are sketched with conventional sign towards
right or left of the central line
* All measurements should be recorded as soon as they are taken
* Offset measurements are written close to the points offseted and exactly opposite to and in line
with the Chainages from which they are taken
* Tie or subsidiary station along a chain line should be indicated by a circle or ovalround.
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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LEVELING
Leveling is the process by which differences In height between two or more points can be
determined
Leveling is a branch of surveying, the object of which is to find or establish the elevation of a given point
with respect to the given or assumed datum (referencepoint)
Common leveling instruments include the spiritlevel, dumpylevel, digitallevel
Definitions:
Level surface:
Defined as a curved surface which at each point is perpendicular to the direction of gravity at the
point .the surface of a still water is a truly Level surface.
Level line:
A level line is a line lying in a level surface. It is therefore, normal to the plumb line at all point
Horizontal line:
It is straight line tangential to the level line at a point. It is also perpendicular to the plumb line
Datum
Datum is any surface to which elevations are referred. Mean sea level afford a convenient datum
work over.
Elevation:
The elevation of point on or near the surface of the earth is its vertical distance above or below an
arbitrarily assumed level surface or datum
Mean sea level:
Is the average height of the sea for all stages of the tides. At particular place it is derived by
averaging the hourly tide heights over a long period of 19 years
Benchmark:
Is a relatively permanent point of reference whose elevation with respect to some assumed datum is
known. It is used either as starting point for leveling or as a point upon which to close as a check.
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Station:
In leveling, a station is that point where the level rod is held and not where level is set up
Height of Instrument
Is the elevation of line of sight with respect to assumed datum
Back sight (B.S)
Sight taken on a rod held at a point of known elevation, to ascertain the amount of by which the
line of sight is above that point and thus to obtain the H.I. Also known as plus sight, as the back
sight reading is always added to the level of datum to get the height of instrument
Fore Sight ( F.S)
Is a sight taken on a rod held at a point of unknown elevation. Also known as minus sight, as the
fore sight reading is always subtracted from the height of instrument to get the elevation of that
point
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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Principles of leveling
The fundamental principle of leveling lies in finding out the separation of level lines passing through
a point of known elevation (B.M.) and that through an unknown point (whose elevation is required
to be determined).
With reference to Figure 13.1, let X represents a point of known elevation (Hx) or a B.M. and Y be a
point whose elevation is required to be determined. To find out the unknown elevation of Y, a level
is set up at L in between X and Y. A leveling staff is first held at X and a reading hx is observed, by
sighting the staff (held vertical to the line of sight of the level). The staff reading at Y, say hy is then
observed. The elevation of the point Y (say Hy) is thus given by Hx + (hx ~ hy) i.e., known elevation
(Hx ) added to the separation of level lines (hx ~ hy) passing through the points.
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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METHODS OF LEVELLING
Leveling methods are subdivided into two major categories: DIRECT and INDIRECT. Direct
leveling describes the method of measuring vertical distance (difference in elevation) directly
with the use of precise or semi-precise leveling instruments. Indirect leveling methods, on the
other hand, apply to measuring vertical distances indirectly or by computation. Unlike
directleveling operations, indirect leveling operations do not depend on lines of sight or
intervisibility of points or stations. Some of the surveying instruments commonly used for
indirect leveling methods is the transit and theodolite.
a) Spirit Leveling or Direct Leveling :
b) Trigonometric leveling or Indirect leveling
c) Barometric leveling
Spirit Leveling or Direct Leveling





Direct leveling is sometimes referred to as “spirit” or “fly” levels.
Uses the measured vertical distance to carry elevation from a known point to an unknown
point.
Direct measurement,
Direct leveling is the most precise method of determining elevation and yields accuracies
of third or higher orders
most commonly used; types:
Trigonometric leveling or Indirect leveling

Applied to determine the elevation of point which is some distant apart from B.M i.e., the
unknown elevation of a point cannot be determined in a single set up of an instrument. Thus,
in this method, instrument gets setup number of times to observe reading along a route in
between observed points. For each set up, staff readings are taken back to a point of known
elevation (first sight from the B.M and forward to a point of unknown elevation) final sight
to the terminal station.



It requires a series of instrument setups along the survey route
By measuring vertical angles and horizontal distance;
Less precise
Barometric Leveling



Based on atmospheric pressure difference;
Using altimeter;
Very rough estimation.
MOHAMED SUHAIL T, Asst Professor Civil, MESCE Kuttipuram
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LEVELLING INSTRUMENTS
The instruments commonly used in direct leveling are
1. Level
2. A leveling staff
Level
The purpose of a level is to provide a horizontal line of sight. Essentially, a level consists of
following four parts:
1.
2.
3.
4.
A telescope to provide line of sight
A level tube to make the line of sight horizontal
A leveling head to bring the bubbles in its centre of run
A tripod to support the instruments
There are following chief types of levels
i.
ii.
iii.
iv.
Dumpy level
Wye Level
Reversible level
Tilting level
FIELD BOOK
A field book, also called level book is being used for taking down each staff reading during leveling
and subsequently, used for finding out the elevation of points/ stations. There are two types of level
books (Table 13.1 and Table 13.2).
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Reduction of Level
The observed staff readings as noted in a level book are further required to be manipulated to find
out the elevation of points. The operation is known as reduction of level. There are two methods for
reduction of levels:
I.
Rise and Fall method and
II.
Height of instrument method
Height of instrument methods
Withreferencetofigure,letXrepresentspointofknownelevation(Hx),oraB.MandYbeapointwhoseelevat
ionisrequiredtobedetermined.TofindouttheunknownelevationofY,alevelissetupatLinbetweenXandY.
Aleveling staffisfirstheldatXandareadingHxisobserved,bysightingthestaff
(heldverticaltothelineofsightofthelevel).ThestaffreadingYsayhyisthenobserved.Theelevationofthepo
intY(sayHy)isthengivenbyHx+(hx,-hy)i.e,knownelevation(Hx)addedtotheseparationoflevellines(hxhy)passingthroughthepoint.
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MODERN
SURVEYING
INSTRUMENTS
● ELECTRONIC DISTANCE METER
● DIGITAL LEVEL
● TOTAL STATION
● GPS
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Electronic Distance Meter
Measurement of distance is accomplished with a modulated microwave
or infrared carrier signal, generated by a small solid-state emitter within
the instrument's optical path, and bounced off of the object to be
measured. The modulation pattern in the returning signal is read and
interpreted by the onboard computer in the EDM. The distance is
determined by emitting and receiving multiple frequencies, and
determining the integer number of wavelengths to the target for each
Frequency.
Principle
In EDM the beam of light is the carrier and which is reflected
back from mirror located at the other end. Such instrument
are less expensive because one active instrument and battery
are only needed at one end and instrument at other end is
simply a reflecting mirror centered over ground centre mark
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Hand held EDM
● Very handy
● Cheap
● Can be used with accuracy
● of 10mm or so
● Rapid measurement
● Long range
● High accuracy
● Measurement of moving
● target
TOTAL STATION
Basic Principle
A total station integrates the functions of a theodolite for
measuring angles, an EDM for measuring distances, digital
data and a data recorder. All total stations have similar
constructional features regardless of their age or level of
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technology, and all perform basically the same functions.
Basic principle of total station
Features:-
● Total solution for surveying work,
● Most accurate and user friendly,
● Gives position of a point (x, y andz) w. r. t. known point (base point),
● Measures distance and angles and
● displays coordinates,
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● EDM is fitted inside the telescope,
● Digital display,
● On board memory to store data,
● Compatibility with computers,
● Measures distance and angles and displays coordinates,
● Auto level compensator is available,
● Can work in lesser visibility also,
● Can measure distances even without prismatic target for lesser
distances,
● water proof,
● On board software are available,
● Can be used for curve layout after feeding data.
Total Stations can be used for:
● • General purpose angle measurement
● • General purpose distance measurement
● • Slope measurement
● • Provision of control surveys
● • Contour and detail mapping
● • Setting out and construction work
● Angular accuracy up to 1”
● Distance measured with laser up to 2 KM
● Distance measured with infrared rays up to 4 KM.( with single prism)
● Capable of storing up to 20,000 points.
Components Of Total Station
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● EDM
● Electronic theodolite
● On-Board Micro-processor
● Data Collector
● Data Storage
● Prisms
Advantages of Total Station over Conventional
instruments:
1. Traditional survey methods are laborious and time consuming
2. Fully automatic electronic measurement
3. Digital display of staff reading and distance
4. Data storage in instrument possible
5. Direct transfer to personal computer of data stored in instruments
6. Online operation through integrated interface to computer
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Disadvantages
● Total stations are dependent on batteries and electronics. The LCD
screen does not work well when it is cold.
● Battery life is also short, batteries and electronics both do not work well
when wet.
● Loss of data is an important consideration
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3. SURVEYING WITH GPS
Within the span of few years of its operation, GPS has truly revolutionised the field of
surveying, with its potential to replace many conventional surveying techniques in use today.
The different methods of surveying with GPS will be briefly described here, along with a review
of GPS instrumentation and method of computation of geodetic and map coordinates from the
GPS observations.
3.1 Methods of Observations
The different methods of observations with GPS include, absolute positioning, relative
positioning in translocation mode, relative positioning using differential GPS technique, and
kinematic GPS surveying technique.
3.1.1 Absolute Positioning
In the absolute positioning mode, the absolute coordinates of the antenna position (centred
over the survey station) are determined using single GPS receiver, by a method similar to the
resection method used in plane tabling. The pseudo ranges (the satellite-antenna range,
contaminated by the receiver clock bias) from minimum four satellites are observed at the given
epoch, from which the four unknown parameters - the 3-D position of the antenna (x, y, z) and
the receiver clock error can be determined. The accuracy of the position obtained from this
method depends upon the accuracy of the time and position messages received from the
satellites. With the selective availability operational, the accuracy of absolute positioning in
real-time was limited to about 100 metres, which has now improved to a about 10 to 20 metres,
since the SA is switched-off. This can be further improved to few centimetres level by using
post-processed satellite orbit information in the post-processing mode. The accuracy of absolute
positioning with GPS is limited mainly due to the high orbit of the satellites. However, very few
applications require absolute position in real time.
3.1.2 Relative Positioning
In the translocation mode (See Figs. III & IV), with two or more GPS receivers observing the
same satellites simultaneously, many common errors, including the major effect of SA get
cancelled out, yielding the relative positions of the two or more observing stations to a very high
level of accuracy. The length of the baseline between two stations, and also the absolute position
of one of the stations, if accurate position of the other station is known, can be obtained to cmlevel accuracy, using carrier phase observations. In differencing mode of observations, using
single difference (difference of carrier phase observations from two receivers to the same
satellite), double difference (between observations from two receivers to two satellites) and
triple difference (difference of double differences over two time epochs), effect of many errors
such as receiver and satellite clock errors etc., can be minimised. (see Fig. VI). Use of dual
frequency observations (both L1 and L2 frequencies) eliminates the major part of ionospheric
effect on the signal, thus improving the accuracy of positioning. With accurate satellite orbit
information, and use of such refined data-processing and modelling techniques, few mm to cmlevel accuracy is possible even in regional or global scale surveys.
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3.1.3 Differential GPS
A modification of the relative positioning method is the differential GPS (DGPS) technique,
where one of the two receivers observing simultaneously is equipped with a transmitter and
other receiver(s) can receive the messages given by this transmitter. The transmitting receiver is
kept fixed on a point whose location is known to high degree of accuracy. Based upon this
position, the receiver computes corrections to the range/phase observations from a GPS satellite,
and transmits them to the other receiver, which can apply these corrections to improve the
accuracy of its own position computed from GPS observations. Such a system is suited for
applications such as vehicle guidance system, locating fishing boats close to the seashore, etc.
The limited range of the transmitter restricts the use of such system to few km. However,
satellite-based DGPS services, now commercially available, remove these restrictions on the
DGPS technique, making possible Wide Area DGPS.
3.1.4 Kinematic GPS
In the Kinematic GPS technique, one of the receivers is in relative motion with respect to
the other receiver, having been mounted either on a vehicle, ship or aircraft. Even with the
difficulties encountered in obtaining the constantly changing position of the moving receiver, the
method also offers some advantages over static surveying, including the ease with which the
ambiguity resolution (estimating the whole number of wavelengths in the phase observable) can
be done. This technique has a number of important applications, including ship and aircraftnavigation, photogrammetric survey control, etc.
3.2 GPS Receivers
A wide variety of GPS receivers are commercially available today. Depending upon the type
of application, accuracy requirements and cost factor, the user can select the type of GPS
receiver which best suits his demands. The receivers available cover a wide range from the
high-precision Rouge receivers developed by the Jet Propulsion Laboratories, (JPL), of the
National Aeronautics and Space Administration (NASA), with built-in atomic clock, to the
hand-held navigation receivers used by Army personnel, mountaineers, etc., which can give the
position to few-metres accuracy. Even wrist-watches with built-in GPS receivers are now
commercially available (e.g.: the Casio GPS watch).
3.2.1 Navigation Receivers
These receivers are normally single-frequency, C/A code, hand-held light weight receivers,
which can yield the position with a few-metres to few tens of metres accuracy. Single channel
receivers, which can track 4 or more satellites by either sequential or multiplexing technique,
which were more common in this category, are now being replaced by two or five channel
receivers. These receivers are very much portable, weighing only few hundred grams, and are
fairly inexpensive, being in the few hundred U.S. dollars price range. Examples of such
receivers are the Magellan 5000 GPS receiver marketed in India by ROLTA (India), the
NAVSTAR GPS PC card that can be fitted in personnel computer, marketed in India By
Micronics Ltd., the Casio portable GPS receiver in a watch, etc. The accuracies in positioning
obtained by these type of receivers are in the range of few tens of metres in absolute positioning
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(in the absence of SA), and few tens of cm in relative positioning, over short baselines of few
km.
3.2.2 Surveying Receivers
The surveying type of receivers are single frequency, multi-channel receivers, which are
useful for most surveying applications, including cadastral mapping applications, providing
tertiary survey control, engineering surveys, etc. These are more expensive than the navigation
type of receivers, and more versatile. The data from many of these receivers can be directly
imported in to most commonly used GIS software packages / formats. Most of these receivers
can also be used in DGPS mode. Examples of surveying receivers are the PRO-XR model of
Trimble Navigation Ltd., the SR 100 model of Leica Ag., etc.
3.2.3 Geodetic Receivers
The Geodetic receivers are multi-channel, dual-frequency receivers, generally with the
capability of receiving and decoding the P-code. They are heavier and more expensive than the
navigation and surveying receivers, ranging from the Rouge receivers installed at the GPS
tracking stations, to the portable geodetic survey control receivers. They are capable of giving
accuracies of the order of few cm-level in absolute positioning with precise post-processed
satellite orbit information and of few mm-level in relative positioning. Examples of such
receivers are the 4000 SSE of Trimble Navigation Ltd., the WILD 200 of Leica, and ASHTECH
Z-12 geodetic receivers, etc.
3.3 Computation of coordinates
From GPS observations, it is possible to obtain the Cartesian rectangular coordinates : X, Y,
Z, in an ECEF global reference system. Often, the users require the coordinates of points in
some local reference system - either geodetic latitude, longitude and height, or grid coordinates.
Hence, transformation of coordinates from the global system to the local system is necessary.
3.3.1 Transformation from Global to Local Datum
The GPS coordinates are in the global World Geodetic System, 1984 (WGS84) developed
by the Defence Mapping Agency (DMA) of U.S.A. These need to be transformed to the local
datum in use in the particular country, e.g. Everest Ellipsoid in India. The transformation of
coordinates involves seven transformation parameters - the three translations due to shift of
origin, three rotations due to change in orientation (which are theoretically zero due to the axes
being parallel) and a scale factor due to the different dimensions of the two reference ellipsoids.
These transformation parameters must be estimated, using coordinates of several welldistributed stations in both the systems, in order to obtain the geodetic coordinates in local
reference system. The values of these parameters, as evaluated by DMA for several local
geodetic datums in the world, are given in Table 7 of [DMA, 1987], which need to be refined by
rigorous computations and using additional data, in order to achieve a high level of accuracy in
coordinates.
3.3.2 Geodetic Coordinates to Map Coordinates
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The conversion from geodetic coordinates (latitude, longitude and height) to the grid
coordinates on Indian topographical gridded maps (easting, northing and height) is described in
[Thompson and Bomford, 1930]. It involves the transformation from the local geodetic system
to the grid system superimposed on the map projection. The map projection used for Survey of
India topographical maps is the Lambert conformal polyconic projection with two standard
parallels, and the rectangular grid system is the Lambert Grid for India. Standard computer
programmes are available for this transformation.
3.3.3 GPS Heights and Mean Sea Level Heights
The height deduced from GPS observations is the ellipsoidal height - height of the
observation point above the reference ellipsoid. The geodetic height of a point is the geoidal
height - height above the geoid, commonly termed as Mean Sea Level (MSL) height. These two
are related by the simple equation:
MSL Height (h) = Ellipsoidal Height (H) - Geoidal Undulation (N)
The geoidal undulation (geoid - ellipsoid separation) is derived from astro-geodetic or
gravimetric data, the accuracy of which is limited to few cm. World Gravity Models are
available for computing the value of N at the observation station. Thus, the MSL heights
computed from GPS data will contain the error in the value of N, limiting its accuracy.
However, in differential GPS levelling, due to cancellation of a large part of this error, the
relative heights can be determined to a much higher accuracy. The estimated precision of
determination of heights using GPS is about 1.5 times the precision of horizontal component.
ELECTRONIC DIGITAL LEVEL
ELECTRONIC DIGITAL LEVEL
The “Electronic Eye” Makes Error-Free Measurements,
Increases Speed, Accuracy and Productivity!!
TOPCON’s takes accuracy and ease of operation to a higher levelwith its
Advanced Image Processing Technology. The outstanding features makethe
DL-101C/102C ideal for high precision applications including the performanceof
1st and 2nd order leveling and deformation monitoring.
(precision digital level)
*Accuracy (Standard deviation for 1km)
Electronic reading: 0.4 mm (w/Invar Staff)
Optical reading: 1.0 mm
*Least count: 0.1mm/0.01mm
(engineer’s digital level)
*Accuracy (Standard deviation for 1km)
Electronic reading: 1.0 mm (w/Fiberglass Staff)
Optical reading: 1.5 mm
*Least count: 1mm/0.1mm
MAIN FEATURES
Faster Automatic Measurement
OPERATING FUNCTIONS
/SOFTWARE
The fully automatic
measuring ability and
digital display of the DL101C/102C excludes any
reading errors, writing mistakes in the field book, and other
possible human-made errors. Consequently, the electronic
measurement data is always more precise and more reliable as
compared to the conventional visual measurement.
◆ N-times measurements
(to get averaged result and standard deviation)
◆ Horizontal distance measurement
(to the staff)
◆ Height determination of intermediate points
◆ Calculation of difference in elevation
(from the Backsight to the Foresight)
◆ Design elevations can be recalled from the PCMCIA card and a
count down to zero for stake out the height is displayed.
◆ Repeat measurement for recollection
◆ Modification of point number
(before foresight measurement)
◆ Selectable minimum units for reading
(DL-101C: 0.1 mm/0.01mm, DL-102C: 1mm/0.1mm)
◆ Manually input data
◆ Alpha/Numeric input function
◆ Swing correct function to reduce the effect of vibrations. This
ensures accurate and stable reading even under windy or heavy
traffic conditions.
◆ Alarm function when distance between Foresight and Backsight is
out of tolerance.
Increased Productivity up to 50%
BF-FB, BB-FF Measurement
When used with TOPCON’s unique patterned staff, height and
distance can be automatically determined digitally by the DL101C/102C.
Since it’s a fully automatic electronic measurement, there is no
need to make an optical reading! You just sight the staff, focus,
and press the measurement button. It’s that simple! The results
appear in the clearly visible display window after about three
seconds.
Highly Accurate
Measurements
With TOPCON’s DL-101C/102C, all leveling work can be
carried out automatically, quickly and more economically as
compared to the performance of conventional optomechanical
levels. This effortless and error-free measurement makes it
possible to have up to a 50% increase in productivity.
PCMCIA Memory Card System
The PCMCIA world standard memory card system can be used
with DL-101C/102C. Memory cards up to 2MB are available
for memory storage in addition to the instrument’s internal
memory capacity of 256KB. The internal memory can store up
to 8,000 levelled points. The PCMCIA memory card slot is
concealed behind the
battery compartment.
This ensures watertight
protection of the
PCMCIA card. Data
recording directly to either
internal memory or
PCMCIA card is selectable.
Screen Backlight
The display screen has a software controlled backlight that can
be set on or off and brightness control at 9 levels to ensure easy
viewing of the screen in bright, shadow and dark conditions.
5m staff
Levelling staffs of a variety of materials and length are available
with the special Topcon pattern to allow Digital Measurements
with DL-101C/102C.
Data Output Function
Standard RS-232C port provides an instant communications
link with a data collector or direct output to a personal
computer.
In addition to the general procedure of Backsight → Foresight, the DL101C/102C has two other collections procedures. Either Backsight 1 →
Foresight 1 → Foresight 2 →Backsight 2 or Backsight 1 → Backsight 2
→ Foresight 1 → Foresight 2 methods can be used. Using these
measurement
techniques, you can
make your
measurements more
Backsight
Foresight
accurate.
;;;;;
Inverse Staff Mode
When heights of elevated points are required to be measured eg. For
ceiling heights, or in tunnels etc., the DL-101C/102C can measure the
height from the ceiling points with staff inverted, using the “reverse
reading” mode.
Inverse Staff Mode
is effective for any
–b
application in which
the height is
measured from
a
elevated points.
ADVANCED APPLICATIONS
◆ Network leveling
The performance from 1st to 4th order leveling
◆ Deformation monitoring
Monitoring and surveillance of ground subsidence.
◆ Industrial surveying
◆ Topographical surveys
Line leveling, Area leveling, Leveling networks, Contour-line surveys.
◆ Road and Rail-laying construction
Longitudinal profiles, Cross-sections, Setting-out of heights
◆ Tunneling and mining