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REDEFINING THE HORIZONTAL & VERTICAL
CONTROL IN INDIA, GCPs, DATUM
TRANSFORMATION, UPDATION OF LAND RECORDS
: CONTRIBUTIONS OF SURVEY OF INDIA
U. N. Mishra
Director
Geodetic & Research Branch

Activities of Geodetic & Research Branch
Responsible
to
Provide
Horizontal
and
Vertical
Control
Determination
of
Transformation
Parameters –
between WGS-84
and Everest. These are available
with G&RB
GCP Library Project – About to complete
Antarctica Expedition – Participation since 1990-91
91
National GPS Data Centre –Analysis
of GPS data
received from Permanent Stations in India
Real Time GPS Data Centre – Receiving GPS data
from Tidal Ports in India
Redefinition of Indian Vertical Datum

Activities of Geodetic & Research Branch
Contd.
Geodetic & Geophysical
studies-Gravity,
Geomagnetism
Astronomical
Observations-Determination
of
True North
Collection, processing and archiving of Tidal
Data along the Indian coast.
Publication of Indian Tide table and Hugli river
tide tables every year in advance.
Redefinition of Indian Vertical Datum
Data dissemination
Capacity building/Training

Requirement of Datum and Coordinate System
To perform surveying and Mapping a datum
and coordinate system is required.
4

What is Datum?
A
datum
(plural
datums)
is a reference
from
which
measurements are made.
It is an associated model of the shape of the earth (ellipsoid) to
define a Geographic Coordinates.
Horizontal datums are used for describing a point on the
earth’s surface, in latitude and longitude or another coordinate
system.
Vertical datums measure elevations or depths.
5

Datum used in Surveying:
Horizontal Datum- (Ellipsoid)
Vertical datums – (Geoid/MSL)
6

Geoid
Figure of Earth
Geoid (Close to
MSL)
2/15/2012 7

Actual shape of earth
2/15/2012 8

The Ellipsoid
The Geoid is a complicated surface defined by infinite
number of observed gravity points, hence not suitable to
perform mathematical computations.
The ellipsoidal surface is smooth and convenient for
mathematical operations.
Therefore ellipsoid is widely used as the reference surface
(datum) for horizontal coordinates in geodetic network.
2/15/2012 9

Ellipsoid (Best Fit Mathematical Surface)
Figure of Earth
Ellipsoid (GRS80)
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Horizontal Datum:
An Ellipsoid is Used as Horizontal Datum.
Its centre coincides with the centre mass of the
earth.
Its minor axis is parallel to the axis of rotation
of the earth.
Everest ellipsoid was used as a Horizontal
datum in India and adjacent countries
2/15/2012 11

Everest Ellipsoid
Evolved from measurement of great Meridonial arc from
Kanyakumari to Banog near Mussoorie.
Arc closely passes through 78 0 E Meridian.
Col. Lambton started the observation of Great Arc on 10 April
1802 from St. Thomas Mount, Madras by measuring a base line
of 40006.4 feet (12194m)
m).
Sir George Everest in 1830 concluded the task of Great Arc
measurement by
computing the parameters of the Ellipsoid
which was named after him.
The values are as under
a = 6377301.243m
b = 6356100.231
231m
f = 1/300.8017
2/15/2012 12

2/15/2012 13

World Geodetic System 1984 (WGS-84)
For all practical purposes, the GRS80
and WGS84
ellipsoids are identical.
WGS84
was designed to be a practical standard global,
geocentric horizontal datum for:
Mapping
Charting
Geodesy and
Navigation
2/15/2012 14

Bureau International de l’Heure (BIH)
WGS84 Ellipsoid
2/15/2012 15

Best Fit Ellipsoid and Geocentric Ellipsoid
Figure of Earth
Geoid (Close to MSL)
Locally Best-fit Ellipsoid
(Everest Ellipsoid)
Centre of Mass of
Earth
Geocentric Ellipsoid
(GRS80)
2/15/2012 16

International Terrestrial Reference Frame (ITRF)
In the Surveying terminology, a reference frame is a set
of points with their coordinates which realize an ideal
reference system
The International Earth Rotation Service (IERS) mission
is
to
provide
internationally
accepted
terrestrial
reference systems
ITRF is produced by IERS
The ITRF is realized through the global Cartesian coordinates
and linear velocities of a global set of sites equipped with
various space geodetic observing systems.
The space geodetic techniques used at present are LLR, SLR,
VLBI, GPS, and DORIS (Doppler Orbitography and Radio-
positioning Integrated by Satellite, is a French precision
navigation system)
2/15/2012 17

IGS
The International GNSS Service (IGS) is a voluntary federation of
many worldwide agencies
IGS collects, archives, and distributes GPS observation data sets of
sufficient accuracy to satisfy the objectives of a wide range of
applications and experimentation.
IGS has a number of components:
an international network of over 500 continuously operating dual-
frequency GNSS stations
More than a dozen regional and operational data centers
three global data centers
seven analysis centers and a number of associate or regional analysis
centers
2/15/2012 18

IGS Stations
2/15/2012 19

Status of Horizontal Control in India - Past
Old Geodetic Triangulation
GT Triangulation was started on 10 th April, 1802 with an aim
to
design a Horizontal
datum
for
India
and
adjacent
countries
Observation – Theodolite for angular and Invar wire for
linear measurements
Layout – Geometrical
figure
adjustment can be performed
and
network
so
that
Result – Everest Ellipsoid as Indian Geodetic Datum,
Horizontal
coordinates
for
surveying
and
mapping
activities
In all 2873 GT stations in India situated on high hill tops.
Present status – Switch over from Everest to WGS-84

Status of Horizontal Control in India - Past

Status of Horizontal Control in India - Past
Number of Series of Indian Triangulation – 37
Primary and 57 Secondary.
One Series is adjusted within it but most of the
series
are
not
adjusted
among
themselves
resulting in mismatch at junctions.
Accuracy
achieved
is
inferior
compared
accuracy achieved through GPS technology.
to

Status of Horizontal Control in India - Present
GCP Library Phase - I
The Phase-I consists of about 300 points spacing about 250 to 300
km apart
These points will serve as the framework for geodetic control for
entire country.
These points has permanent monumentation.
GPS observations have already been completed using Dual
frequency GPS receivers on all these stations in static relative
mode w.r.t. IGS
Geodynamics Studies).
Stations
(International
GPS
Stations
for

GCP Library Phase – I
Monument
Design of GCP Library Phase-I Monument

GCP Library Phase-I: Distribution in India
1 Andhra Pradesh 21
2 Assam & Nagaland 11
3 Bihar 9
4 Chhattisgarh 8
5 Delhi 1
6 Gujarat, Daman & Diu 22
7 Haryana 6
8 Himanchal Pradesh 7
9 Jammu & Kashmir 10
10 Jharkhand 8
11 Karnataka 21
12 Kerala & Lakshyadeep 6
13 Madhya Pradesh 18
14 Maharashtra & Goa 24
15 Meghalaya & Arunachal Pradesh 6
16 Orissa 11
17 Punjab & Chandigarh 7
18 Rajasthan 25
19 Tamilnadu, Pondi, A&N Islands 16
20 Tripura, Manipur & Mizoram 6
21 Uttar Pradesh 22
22 Uttarakhand 15
23 West Bengal & Sikkim 11
Total 291

Achievements: GCP Phase-I
Phase-I:
Observations on 291 stations in different states is
completed
Coordinates of all points has been computed using
Bernes 5.0 software with reference to IGS stations in
ITRF 2008 (Epoch 2005)

Subsequent Phases Of GCP Library
Phase-II
The control is being densified by providing 2200 points at the spacing of 25 to
30 km
This task is under progress and following states have already been covered
Phase-III
HP, Haryana, Punjab
MP, UP, Bihar (North)
Maharastra, Gujrat
Karnataka, Kerala, Tamilnadu
Andhra Pradesh, Orissa, WB
Uttarakhand
Rajasthan: GPS Observation is in Progress
Control will be further densified by regional directorates of Survey of India at
the spacing of 8 to 10 km (about 7000 points)

Subsequent Phases Of GCP Library
Phase-II
States where observations has to be done in next a few months
Chattisgarh, South Bihar, Jharkhand (Naxalite
Belt area)
J & K State
North Eastern States including Sikkim.

Achievements: GCP Phase-II
Phase-II
Observations has been completed in the following states
Name Of State
No. of Phase II GCP Observe
Punjab, Haryana, Himachal (31+35+22) = 88
MP, UP, Bihar (178+84+50) = 312
Maharastra, Gujrat (219+145) = 364
Karnataka, Kerala, Tamilnadu (132+45+106) = 283
AP, Orissa, WB (244+95+67)= 406
W UP and Uttarakhand 86
Rajasthan (work in progress) 100
Total GCP Observed 1639

Achievements: GCP Phase-II
Field work will
start in June / July
Work in Progress 2012
Field work will
start in 3 rd week
of Feb 2012

Network Adjustment Strategy
Coordinates of CORS will be computed with reference to ITRF 2008 (Epoch2005) coordinates of
IGS Stations. Here epoch referes to the co-ordinates
ordinates of IGS station on 1 st January, 2005. We are
adjusting the co-ordinatesordinates of 1 st
phase points with reference to Permanent Continuous
Operating Reference Stations (CORS). As we know that the Indian plate is moving like other
plates of earth due to plate tectonic. It is also seen that Indian plate is having appreciable
velocity of the order of 5-6 cm par annum.
If we adjust our Ist Phase points with respect to our permanent CORS better adjustment will
result under appreciable velocity of Indian plate.
IGS
(HYDE)
CORS
Phase-I
Phase-I
IGS
(IISC)
CORS
Phase-I
Phase-I

Contd…
Owing to velocity factor due to movement of Indian
plates the co-ordinates
ordinates of a point will be different in
different
years
but
all
the
co-ordinatesordinates
are
standardised at epoch 2005 in ITRF 2008 reference
frame.
So, co-ordinates
ordinates may be revised after 10 – 15 years to
different ITRF epoch.
User agency should adopt the co-ordinates
ordinates supplied
by SOI only for consistency.

GCP Phase-I Network: Adjusted with reference to CORS
• At present the
network is being
adjusted using the
vendor software.
• However, after
completion of entire
work of Phase-II
also, network is
proposed to be
adjusted using
BIGADJUST
programme as a
measure of
independent check.

GCP Phase-II Network: Adjusted with reference to
Phase-I

Accuracy Expected
Positional accuracy of control points after final adjustment is
expected to be better than
3cm
for Phase-I GCPs
9cm
for phase-II
GCPs and
15 cm cm for phase-III
GCPs

Accuracy Expected
Positional accuracy of control points after final adjustment is
expected to be better than
3cm
for Phase-I GCPs
9cm
for phase-II
GCPs and
15 cm cm for phase-III
GCPs

National GPS Data Centre
National
GPS Data Centre
was setup under Satellite
Geodesy Wing in March 2001 for deformation and plate
motion studies
It has the mandate of receiving, analyzing and archiving of
Permanent GPS stations data across the country
The data is being received and archived from Permanent
GPS stations
This data is available for sharing with
other scientific
organizations for scientific studies.

PANAMIC
JAMMU & KASHMIR
LEH
PUNJAB
NADDI
KOTHI
HIMACHAL
PRADESH
DEHRADUN
HARYANA
HENLE
UTTARAKHAND
INDIAN GPS NETWORK
BHATWAR
I
NATIONAL GPS DATA CENTRES,DEHRADUN
MUNSIYARI
ALMORAI
PITHORAGARH
DELHI
GANGTOK
RAJASTHAN
LUCKNOW
KANPUR
UTTAR PRADESH
BOMDILA
SIKKIM
TEJPUR
GUAHATI
SHILLONG
MUKUKCHUNG
BIHAR
MEGHALAYA
BANGLADESH
IMPHAL
KANDLA
OKHA
PORBANDAR
VERAVAL
VADINAR
GUJARAT
BHOPAL
MADHYA PRADESH
JABALPUR
DHANBAD
JHARKHAND
WEST BENGAL
GARDEN REACH
DIAMOND HARBOUR
HALDIA
SAGAR
ORISSA
BHUBANESHWAR
PARADIP
MUMBAI
JNPT
JAIGARH
ARABIAN
SEA MARMAGAO
KARWAR
MAHARASHTRA
PUNE
GOA
KARNATAKA
GOPALPUR
ANDHRA PRADESH
VISAKHAPATNAM
KAKINADA
HYDERABAD
MACHILIPATNAM
KRISHNAPATNAM
BAY
OF
BENGAL
AERIAL BAY
NEW MANGALORE
BANGALORE
ENNORE
CHENNAI
PONDICHERY
PORT BLAIR
KAVARATTI
BEYPORE
ANDROTH
TAMILNADU
CUDDALORE
NAGAPPATINAM
COCHIN
KODAIKANAL
THIRUVANANTHAPURAM
RAMESHWARAM
MINICOY
TUTICORIN
KANYAKUMARI
NANCOWRY
REFERENCES
CAMPBELL BAY
SOI GPS STATIONS WITH VSAT( OPERATIONAL)
SOI GPS STATIONS WITH VSAT( PROPOSED)
PERMANENT GPS STATIONS

REAL TIME GPS DATA
Under the
modernization of Indian
Tide Gauge Network in Post Tsunami
Scenario,
several
tidal
observatories
across the East & West Coast of India,
Andaman & Nicobar
Islands
and
Lakshadweep
Islands
have
been
established.
20 of these stations are equipped with
dual
frequency
GPS
Receivers
collocated with Digital Tide Gauges.
These stations have Real Time Data
Transmission (RTDT) facilities through
VSAT.
GPS Data is received, archived and
processed at National GPS Data Centre.
REMOTE VSAT SETUP
39

REDEFINITION OF INDIAN VERTICAL DATUM -
DENSIFICATION
GTS
Levelling
was
carried
out
between 1850 to 1905.
Indian Vertical Datum was first time
defined in 1905.
Then no Invar staves were used.
No Fore – Back Levelling was done.
Most of the BMs established then do
not exist on the ground now due to
developmental activities and vagaries
of the weather.
Without Gravity Values.
It was assumed that water level of
Arabian Sea and Bay of Bengal is
same, which is infact different due to
different
salinity
and
consequent
different density.
Levelling was not adjusted in single
all India Level Network.
Hence necessary to Redefine Vertical
Datum.
With
the
requirement
of
height
accuracy within few centimetres and
to achieve water flow criterion, we
needed to redefine vertical datum.

In past, the requirement of contours was 10 m / 20 m in plain
areas and 100 m / 200 m in the hilly area (due to sparse
developmental activities) but now owing to population pressure
and need for faster development for micro level planning,
requirements have increased to get the contour at 50 cm / 1 metre.
We
are
facing more drainage problem, more sewer lines are
required, to solve water problem we need to interlink rivers.
Essential ingredient in all these works is precise vertical control
i.e. precise level line which meets water flow criteria.
To achieve this an initiative to redefine the vertical datum for the
whole country has been taken up. In this project, it is envisaged to
carryout the High Precision Levelling alongwith the gravity
observations to obtain the geopotential numbers.
These newly defined heights will be based on the geopotential
numbers
and
Helmert
Orthometric
Heights
which
are
scientifically correct heights and follows the water flow criterion.

The entire project is divided in two phases:
First Phase : To form the main frame of vertical control for the
entire nation (~45000 Km in both direction).
Second Phase : Based on the main frame of vertical control further
densification of the vertical control will be done (~100000 Km in
both direction).
Phase – I of the Project for Redefinition of Indian Vertical Datum
has been completed.
Phase-II for the densification of Levelling newtwork will be
undertaken on allocation of budget.
Precise Vertical control is also very important ingredient for
national development, so, like any other developed country, India
needs to have this framework at the earliest.
Proposal for allocation of Budget to the tune of Rs. 15 crores has
been submitted for approval.

Interlinking of Rivers.
Flood Control.
MAJOR UTILITIES
Development of efficient Drainage and sewer line system.
Coastal Hazard Line Delineation.
High value infrastructural and engineering projects.

PROJECTS IN PIPELINE
Virtual Reference Station Network –
Corrections issued by a beacon installed at continuous operating
GPS Reference Stations, when received by an observer in the area
of work can find out position with sub-metre
accuracy with single
small portable receiver .
It will enable quick mapping and updation of maps, cadastral
mapping using single receivers.
It can be used for the tracking and navigation (Rail/Road/Air) and
for many other applications such as maintaining accurate land
records and land uses, Infrastructure Project Planning etc.
With GCP Library Stations already in place, such a network is
being conceived and a proposal is in the final stages of preparation
for submission.
It is estimated that total cost of the project will be in tune of Rs
500 crores.

CONCLUSION
Provision of dense control at a spacing of less than 20 km will benefit the
user community in many ways.
The biggest benefit will be the standardisation of our land records, which is
hitherto in very bad shape inviting number of litigations.
So far our land records are mostly on Cassini Projection, which is a
equidistant projection. Distortion of area and shape are functions of distance
from central meridian. Scale is true along central meridian only. Because of
which it can not be used for bigger areas. Therefore, land records are
maintained in pieces and seamless record is not possible/available.
It is envisaged in Land Record modernisation programme of Government
of India that now onwards all the records will be based on Phase I, II and III
GCPs on WGS-84
Datum with UTM Projection. Using GCPs, control will
be brought to village through GPS and thereafter using Total Station
boundaries of land parcels will be measured/demarcated. 45

CONCLUSION
Contd.
Once the GCP Phase-III
Project is completed, denser network of
control will be available.
In future the GCP points are proposed to be equipped with the
facilities to transmit the differential corrections to the user community
in the form of
Reference Station.
Continuous Operating Reference Stations / Virtual