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5 June 2025

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� Application of ETS and use-case of ETS in NAKSHA when GNSS signals are weak

by� Mantu Talukder, Officer Surveyor &

Tarun Deka, Officer Surveyor

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5 June 2025

INTRODUCTION

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• The purpose of any topographical survey is to prepare a map.

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• Control point is the basic requirement of map making process.

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• There are several methods of survey to provide control point and collection of detail.

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SURVEYING METHODS�(For provision of control points)

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Conventional Techniques:

• Triangulation
• Theodolite Traverse
• Levelling, etc.

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Modern Techniques:

• GNSS
• Total Station Survey
• Photogrammetric method

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SURVEYING METHODS�(For Details Survey and Mapping)

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Conventional Techniques:

• Chain surveying
• Plane table surveying

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Modern Techniques:

• Total Station Survey
• Photogrammetric Method
• Remote sensing method
• Drone Survey

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EVOLUTION OF MODERN MAPPING

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MEASUREMENT ENTITIES

• Provision of Control Points, includes the measurement of two entities

Distance and Angle

• Distance can be measured by using various instruments like chain, tape, Steel band, Electronic Distance Measurement etc.

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Angle can be measured by using Theodolite.

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• Once distance and angular measurement is over, computation is performed to provide the control points.

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ELECTRONIC TOTAL STATION

�A Total Station is a surveying instrument that combines:

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• Electronic Distance Measurement (EDM): Measures distances between the instrument and a target
• Electronic Theodolite: Measures angles (horizontal and vertical) with high precision.

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• A Microprocessor,
• An Electronic Data Collector and Display
• A Storage System.

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DIFFERENT PARTS OF TOTAL STATION:

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ACCESSORIES FOR TOTAL STATION

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Tripods

�Prisms

�Tribraches

�Batteries & Chargers

�Data & Power Cables

�Prism Poles

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NAKSHA

"National Geospatial Knowledge-based Land Survey of Urban Habitations" a Pilot project has been come up in 152 Urban Local Bodies (ULBs) across 26 States and 3 Union Territories (UTs) in India

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Field Survey Methodologies under NAKSHA to be followed for ground truthing are:

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• Option-1: Field Data Collector (FDC) with GNSS Rover and CORS Network
• Option-2: Field Data Collector (FDC) with GNSS Rover in Static mode where internet is weak
• Option-3: Field Data Collector (FDC), Electronic total Station (ETS) with GNSS Rover and CORS Network

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WORKING PRINCIPLE of ETS

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• Measure Distance and Angle(Horizontal and Vertical)

of a point

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• Calculate the coordinate using the measured distance, angle and coordinate of the occupied point.

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ACCURACY

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• The angular accuracy varies from1″ to 20 ″.

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• Distance accuracy depends upon two factors.

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1. Instrumental error which ranges from

+ / - 10mm to + / - 2mm.

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b) Error due to the length of measurement.

It can be from + / - 10mm to + / - 2mm per

kilometer.

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ADVANTAGES OF TOTAL STATION

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• Quick and accurate data collection

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• Useful where GNSS signals are weak due to obstacles (canopy cover, buildings etc.), Atmospheric effects, Multipath, Interferences etc.

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• Reduces manual errors

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• Saves time

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• Stores large volumes of data

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• Integration with GIS and CAD software

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SURVEYING METHODS USING TOTAL STATION

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• Detail Surveying (Topographic)

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• Remote Distance Measurement

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• Resection Method

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• Stakeout/Setting Out

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• Remote Elevation Measurement

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• Traverse Surveying

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DETAIL SURVEYING

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• Keep the ETS on a known point.

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• Set up station with the help of another known point.

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• Keep the prism on the points of desired features and measure. (buildings corner, trees, road, boundary corner etc.)

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• Data processed

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• Uses in mapping and planning

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REMOTE DISTANCE MEASUREMENT (RDM)

• The process of finding the distance between two points A & B (which are not inter-visible from each other) from another point ‘I’ (instrument position) is known as RDM.

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• This method is very useful for finding distances between two points which has an obstruction between them. It is of two types- Continuous & Radial.

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• Distances can be obtained either in the Continuous mode i.e., AB, BC,CD, DE, EF etc. or

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• Radial mode i.e., AB, AC, AD, AE, AF etc.

However, the field procedure is same for both only the selection of operation varies.

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RESECTION

• Process of Finding the coordinates of total station position by knowing other points coordinates.

Resection Station

Known Station

Known Station

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STAKE OUT

• Process of Finding the positions of known coordinates points e.g. missing boundary pillars.

ETS

Missing Pillar

Fore Station

Back Station

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REMOTE ELEVATION MEASUREMENT (REM):

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• The process of finding the

height of objects without

actually going to the top of the

object is known as Remote

Elevation Measuring (REM)

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• This feature measures the elevation of a point where a

prism can not be placed directly. The measurement is

extended along the plumb line while the elevation is

continuously displayed.

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TRAVERSE

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• Establishes control networks

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• Measures distances and angles between known points

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• Used for boundaries, roads, and pipelines etc.

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• Open traverse: Starts from a known control point and ends at unknown point.

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• Closed traverse: Starts from and ends at known control points.

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• Closed Circuit traverse: Starts and ends at the same known control points.

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LIMITATIONS

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• Requires line of sight.

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• Affected by weather (rain, fog).

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• Requires trained personnel.

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• Expensive equipment.

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• Very less output as compared to GNSS and Photogrammetric methods.

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APPLICATION

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• Providing Control Points for large scale survey.

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• Boundary Survey.

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• Alignment Survey.

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• Tunnel Survey.

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• Fixing route of river, road, railway line, cannel etc.

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USE-CASE of ETS in FOREST CANOPY

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• Dense tree canopy blocks GNSS signals

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• ETS can be SET UP on clearings of line

of sight or elevated platform to measure

hidden points.

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USE-CASE of ETS in HIGH RISE BUILDING covered area

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• Tall buildings obstruct GNSS signals

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• ETS can be used to measure the corner of the building or any other required points.

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USE-CASE of ETS in Underground Location

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• No GNSS coverage underground.

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• ETS is ideal for tunnels, mines, basements etc.

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USE-CASE of ETS in Industrial area

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• Metal structures cause signal multipath/reflection error.

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• In that case,ETS can be used for precisely locate the position.

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• e.g. Power Plants, Oil Refineries, Shipyards etc.

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USE CASE FOR NAKSHA

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CASE 1: GNSS cannot be used due to weak signals.

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• Provide 2 no of Control points in an open area at nearby location.

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• Setup ETS with the help of the two control points.

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• Measure the points to be surveyed.

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USE CASE FOR NAKSHA

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• CASE 2: GNSS cannot be used due to weak signals and no suitable location available for control points nearby to the area to be surveyed.

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• Provide at least 2 no of Control points in an open area using GNSS.

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• Setup ETS with the help of the two control points.

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• Run a Traverse line near to the points to be surveyed.

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• Through Offset to the desired points.

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Thank you