MODERN SURVEY INSTRUMENTS AND THEIR USE IN MINE SURVEYING

Dheeraj Kumar

Associate Professor, Department of Mining Engineering, I. S. M. Dhanbad Email: dheeraj@dkumar.org

ABSTRACT Although surveying techniques have always played a primary role in collecting data for mapping, recently new Instruments and methods for data capture and processing have introduced the chance to increase the mass and the variety of achievable information. Nowadays real-time monitoring systems based on robotic total stations and GPS, digital photogrammetric techniques, high resolution satellite imagery, satellite, airborne and terrestrial laser scanners devices are able to give a set of powerful tools for the geometric surveying and modeling. The paper focuses the new trends in surveying gadgets and their applications in mine surveying, which has been pushed up in the latest years by the diffusion of the information technology. 1. INTRODUCTION Mine surveyors are involved in every aspect of mining operations; this includes initial exploration, initial construction of mine operations, on-going mining works, rehabilitation of site and abandonment stage after mining is completed. Technological developments in the field of computer science, information technology and satellite technology have created new hopes for surveying and geoinformatics. Whilst it is true that mine surveyors in Deep/Underground mines do also carry out surveys above ground, their main work is carried out hundreds of meters underground. The coming of global positioning system (GPS), total station and digital theodolites has made the acquisition of data much simpler and faster than hitherto was the case. The use of latest mapping technology like Geographic Information System (GIS) and Remote Sensing is growing in Indian Mines. The Remote Sensing technology has been extensively used in mapping the regions affected by underground fires in Jharia and its surrounding areas. This technology integrated with GIS, has become an effective tool for developing and implementing a rehabilitation plan for the region. In particular this paper is focused on the new trends in surveying gadgets and their applications in mine surveying, which has been pushed up in the latest years by the diffusion of the information technology, capable of measuring points as far as a few hundred meters from the instrument standpoint to the site to be studied with the desired precision. 2. MODERN SURVEYING INSTRUMENTS One Second Theodolite One second Theodolite is a precise horizontal angle measuring instrument with a least count of 1” and is widely used for surface and underground traversing. General features These theodolites are of transit type with a micrometer fitted to it. The centering is done with the help of an optical plummet. It is suitable for almost every type of survey work. It has a well-illuminated optically reading system. A micrometer screen is attached with it. With the help of this micrometer screw or fine adjustment screw the accuracy of the reading taken are increased. Here the instrument possessing least count of 1”. It has the major advantage in the case of measuring the horizontal angle

or vertical angle. In gassy mines where the total station may not be permitted, precise angular measurement can be made with these theodolites Precautions

• Necessary adjustment are to be done • Not to be used directly under the sun

GPS in Mining The standard surveying method has been with a traditional total station, requiring a minimum of two survey personnel for each crew. But it is slow compared to GPS surveying and requires users to set multiple control points in sight of where the survey work is to be performed. The Global Positioning System (GPS) is a worldwide satellite-based system that can be used to measure the three-dimensional position of a point anywhere on Earth. The system uses over twenty orbiting satellites, so that anywhere in the world and at any time there will be enough satellites in the sky above to reliably measure the position of a portable satellite receiver. One receiver can be used to obtain low accuracy positions, while two or more receivers and advanced data reduction techniques can be used for high accuracy work.

GPS can be very well used in mine surveying in opencast mines only . It is a tool which can determine on its own without any relation to the topography or otherwise the position which it occupies both in respect of meridian and datum. What all needed is open sky, minimum 4 satellites and proper selection of the method of survey. GPS gives the location of the Base or GPS Rover Antenna point in term of Geodetic Co-ordinates or Cartesian Co-ordinates with the help of satellites signals orbiting the earth in different orbits. GPS like any other precise survey instrument can be mounted on a tripod and centered on the exact point whose location is required. GPS receiver data can be transferred to a computer, which has post processing software programs. The programs calculate the positions and heights of points in the desired grid system through suitable transformation software. The advantages of using the satellite based GPS techniques for surveying are:

� GPS measurements do not require inter-visibility between points whereas the conventional surveying tools require line of sight for measurements.

� GPS technique provides a three dimensional position for the point. That is in one go, we get the horizontal and vertical position of the point, unlike in conventional surveying where we need two operations viz., horizontal traverse for planimetric control and a level loop for height control.

� A very high accuracy measurement can be made in a relatively short time for baseline lengths of a few hundred meters to few hundred kilometers and can provide the same accuracy anywhere on earth, in almost any weather condition and at any time of the day.

GPS offers many advantages compared with conventional survey methods. Because there is no need for a rod person, each surveyor can work alone when necessary. GPS also requires much less setup time than did traditional surveying equipment, so the crew can use its time more efficiently. It can also keep a much more flexible schedule and move from one area to the next or one pit to another as needed.

Fig.1 GPS model 1200 (Leica) and SR 20 (Leica) The possible fields of GPS application in mine surveying may be

1. Establishing National Grid bases at new areas: 2. Establishing boundaries in case of mining lease areas 3. Documentation of land holdings 4. Establishing control stations around OCPs 5. Training the present generation to face future challenges 6. Other applications

a. Surveying the positions of benches b. Surveying the positions of the working faces, (to monitor the production) c. Monitoring the Positions of Machines in the Mine, d. Measurement of O.B. Dumps. e. Measurement of Stock piles, f. Detail Surveying on the Surface, g. Monitoring the pit slopes for Stability, h. Delineating the position of water in the sump. i. Updating the mine’s Information System (IS) j. Surveying the positions of boreholes, drilling sites etc. k. Strengthening the Survey Control Network.

Limitations

a. Initial high investment. b. Clear view of sky needed, not applicable in underground mines, obstructed sites. c. Disturbances from radio transmissions & Antenna.

Total Stations Total Station is the combination of an electronic distance measurement, electronic theodolite and a programmed calculator and may be said to be an electronic tacheometer theodolite.

Functions

The inclined distance and horizontal & vertical angles to target are measured automatically at a push of button. Distance Electromagnetic modulated beam or wave is generated in the main instrument held at one end of the line to be measured. This modulated beam is directed toward a reflector held at the other end of the line from where it is reflected back toward the main instrument, in a parallel path, where the distance traveled by the electronic signal is determined by measuring the “phase-difference” between the transmitted and reflected signals.

Fig. 2 Total Stations model: S6 (Trimble) [4] and model: 211d (Topcon)

Angle measurement The angle measurement system of the total station in similar to that of an electronic theodolite, the dynamic angle-measuring system used in the total station makes use of a large number of graduation for each reading of the angle on Horizontal or Vertical circle of the instrument. This helps to eliminate as for as possible the effects of graduation errors. The other parameters like horizontal distance, co-ordinates, levels etc. are also calculated automatically and displayed digitally. The display may be alphanumeric and graphic as well. A number of trigonometrical functions and setting out parameters can also be performed. Initial setting parameters like bearing of a line, co-ordinates and height of the station occupied, the height of instrument and that of the reflector height needs to be input in the instrument memory before starting the actual measurement. It can also be used in trekking mode for continuous measurement on a moving reflector for setting out points of interest. Observations A number of functions, settings and adjustments are available in the control panel mounted on the system to set up the Total Station for specific tasks. Co-ordinates, height, and horizontal direction (angle) of instrument stations can be stored in the theodolite and are then available as station co-ordinates for the next traverse stations. 3D Laser Scanning 3D Laser imaging system provides a user with a dense set of three-dimensional vectors to unknown points relative to the scanner location. Given the volume of points and high sampling frequency, laser-imaging systems offer surveyors and photogrammetrists an unprecedented density of geospatial information coverage. For this reason, there is enormous potential for use of this technique in applications where such dense data sets could provide great insight into the valid representation of the region. Mining Industry Applications Two factors that are common in all mining and minerals operations make laser mapping a rapid and cost effective technology for this industry. Firstly, mining involves moving volumes of material from one place to another - and the only way to know what is really going on is to measure the in-situ excavated volume of that material. Using conventional surveying technology, mine surveyors spend a great deal of time surveying spot heights in order to calculate volumes. Secondly, most mines have areas that are difficult to access and are therefore difficult to survey. Laser mapping allows to undertake high accuracy surveys from a safe distance. It gives more detail, which opens up possibilities for using the data in more detailed design work or in geotechnical assessments. A weak link in many projects is the accuracy of the terrain model used.

Typical applications in mining for laser mapping These include to,

• accurately map, model and interpret geological structures in a pit • digitize boundaries, structures and features of interest directly in a 3D spatially correct

environment • export 3D CAD drawings combined with other geological information in external databases • conduct daily or end of month survey - detailed and accurate model of a pit, stockpile or

development face • create points, polygons or lines can be created directly onto the 3D model to accurately

calculate dips and strikes • contract volume measurement, truck and shovel load measurement and analysis • survey for pit production measurement, underground development and void survey • haul road analysis, volume measurement • monitor and analyze and slope stability • conduct rapid pre- and post-blast surveys • conduct airborne surveys for reserves assessments (where topography is critical in shallow

flat lying deposits) • conduct stope surveying

System Requirements 3 D laser scanner (range 2000m, accuracy 25mm) AutoCAD/ GIS software

Fig 3. a LPM-2K Long Range Scanner in use for remote surveying b. LPM-2K Long Range Scanner in use at an open cast coal mine c. Leica HDS3000 scanner Both terrestrial and airborne laser scanners give as an output XYZ coordinates and picture of laser intensity determined by scanning about 6-8 million points easy and accurate become surfaces by using appropriate software. Prepared spatial models could be converted to any commercial CAD and GIS system for post processing. A terrestrial laser scanner determines the distance between a large number of object points and the scanner by emitting laser pulses in different directions and detecting the echoes from the objects. So-called pulsed scanners measure the travel time of the pulse towards an object and back. This technique therefore uses the intensity of the light signal to detect when an emitted signal returns to the scanner. Leica claims an accuracy of 6mm at 50m for the Leica HDS 3000. Opteh ILRIS 3D laser scanner provides dynamic measuring range capabilities (3 m- 1500m) with 6mm distance accuracy. In order to receive accurate information about the point position in plan and height three different measuring systems are used. Combination of GPS- and INS- system provides in every moment the

precise position (WGS coordinates) and orientation (3 angles) of measuring system. The laser scanner only measures distances according to its position. The planimetric accuracy of the laser points is approximately 0.5 m where the point density is up to four points per square meter. The accuracy in height is 0.01 up to 0.15 m. In mines where the direction of mining is consistent and there are suitable vantage points, it is possible to make considerable productivity gains through the use of remote surveying. A long range laser scanner is mounted in a secure position (maybe inside a building looking through a window) at a vantage point over looking the mining area. A standard serial data link (19200 baud) is set up between the instrument and a CAD workstation in the office. It is possible to use radio modems for this purpose. On the CAD system a polygon can be defined outlining the area to be surveyed, along with other scanning parameters. The results of the scan can be seen directly in the CAD system. Both pre- and post-blast measurements, as well as stock pile volumes, can be collected much more effectively using laser scanning technology.

Fig 4. Pre and post blast measurement

Auto Levels

Salient Features of Auto Levels

• Instrument consists chief of the telescope with an optical measuring system. • Mechanical Compensator is essentially a pendulum, supported by tour fixed suspension

tapes and carrying a prism. • Provided the circular bubble, sensitivity 8′ per 2 mm has been in its setting circle by

turning the three foot screws. • Line of sight will be automatically horizontal as the compensator (pendulum) will be well

within its working range of + 15′. • Press button to check the functioning of the compensator. • The eyepiece with di-optic scale is turned to focus the reticule cross hairs. The standard

eyepiece gives 32x telescope magnification. • The reticule has wedged-shaped hairs for precise leveling with the parallel plate

micrometer and inver staffs, and a single horizontal hair for normal leveling staffs; it also has 1:100 stadia hairs.

• The focusing knob is turned to obtain a sharp image of the staff. It has a course and fine motion. Fine pointing is by means of the endless horizontal drive screw. The drive has knobs at each side for use with either hand.

Applications

The sphere of application of Auto Levels extends as follows:-

• Leveling for bench mark for surface and underground. • Leveling for subsidence survey in mining area. • Leveling for large machinery constriction in Civil Engineering job.

Advantages

Following are the advantages of precise leveling instruments.

• They are compact and lighter then old instruments. • Modern auto set levels are more accurate and at the some time quicker also. • The larger magnification of telescope and the measurements by parallel plate

micrometers have enabled the levels to read smaller fractions and therefore has enhanced the accuracy.

• The instruments with the compensators are quicker and at the same time there in ease in reading because of erect image.

• All glass-to-air surface of the optical system are antireflection coated and therefore there is minimum loss of light and the images are bright.

Fig. 5 Auto Level (model: Leica runner 20/24)

Parallel Plate Micrometer

• For precise leveling the parallel plate micrometer is filled in front of the telescope objective and locked in position with the knob.

• By turning the micrometer knob the parallel sided glass plate is tilting in its housing, thereby causing the line of sight to be raised or lowered (i.e. to be displaced in the vertical plane) parallel to itself.

• In the standard metric model, the range of displacement is 10 mm or 5 mm corresponding to the interval or metric wild inver staffs.

• In the micrometer scale, seen in the reading eyepiece, the amount of displacement is read directly in figures to 0.1 mm or 0.05 mm and estimated to 0.01mm or 0.005 mm.

• When the parallel plate is vertical, the line of sight is not displaced. Digital Level Digital levels are generally precise leveling instruments equipped with electronically high-speed camera having coding and decoding facilities in terms of distance and height. The instrument has memorized the coded staff, which may be decoded by visualizing the staff in sufficient width and corresponding measurement by the instrument. Readings are displayed on monitor, stored in instruments as well as PCMCIA Card and may be downloaded to PC with the help of downloading softwares provided with the system. Digital levels provide a tool, which can be quickly learnt and effectively used to complete the leveling work. With the ability to record measurements in as fast as 3 seconds, productivity can be substantially improved.

Using the digital levels one can save up to 50 percent of time and costs, through reduced reading errors, writing errors, calculation of the limits, values - all measurements and calculations are very fast.

Fig. 6 Modern Digital Levels Leica Sprinter and Leica DNA 10 Gyrotheodlite Determination of bearing and transforming it to the underground is a difficult and specialized job in Mine Surveying. The surveyor has to carryout astronomical observations to determine the true bearing on the surface, which is only possible in clear and starry nights. Use of magnetic bearings measured with compass are liable to gross errors and are open to objections because of low accuracy of measurement, variation in magnetic declination and erratic behavior of compass near known or unknown magnetic fields. Transferring of bearing in the underground by conventional methods is a skilled as well as a laborious job and high accuracy is also not achievable. The invention of gyro-attachment has helped in overcoming the above difficulties.

Fig. 7. Gyrotheodlite Gyrotheodlite is a surveying instrument used to orientate an underground survey base line relative to true North. The Instrument is used to find the bearing of any line on the surface or in the underground.

Principle of Gyro The gyro attachment consists of a gyro motor suspended vertically, like a plumb bob on a thin metal tape. Its spin axis is therefore held horizontal through gravity. The gyro motor powered by the accompanying battery unit spins at 22000 revolutions per minute about this horizontal axis and tries to maintain, in space, its initial random spinning plane created by its moment of inertia. The gyro, together with the theodolite and tripod is earthbound and is pulled out of its original spinning plane by the earth’s rotation. The gravity influenced gyro reacts to this interference and its spin axis oscillates about the plumb line until the spin axis is oriented in the meridian plane and the rotation of gyro

corresponds to the rotation of the earth from west to east. As a result there is no interference, but the gyro does not stabilize immediately in north-south direction and oscillates about the meridian plane because of its mass inertia. Shaft Correlation using Nadir Plummet and Laser These are the easy-to-use instrument for defining plumb line very accurately used for maintaining verticality of a deep shaft during sinking, transfer of co-ordinates to U/G working in correlation and other upwards and downwards plumbing operations. Latest development in the instrument is automatic zenith and nadir laser plummet. In conventional method the wire is suspended from top of the shaft to transfer the co-ordinates from surface to ground. With increase in depth this may lead to incorrect correlation. Thus lasers are used which are very precise even at large depths. Laser beam is sent to the shaft bottom for 4 different positions of plummet at 900 apart. Due to very small error in verticality, we may sometimes get 4 different points close to each other. Lines are drawn joining all the diagonal points and the center is found. For greater accuracy, the laser is projected from 8 points by turning plummet through 450.

Fig. 8. Zeiss Nadir Plummet Geographic Information System (GIS) Information collected in the field by surveyors, or from aerial photographs, satellite images, or using GPS, is almost always represented on some type of map. In the past the printed map was the final product used to analyze the information and to make decisions. Nowadays maps are stored as layers of spatial information in a geographic information system (GIS) allowing manipulation, analysis and display of spatial data. GIS links location to information (such as people to addresses, buildings to parcels, or streets within a network) and layers that information to give us a better understanding of how it all interrelates. We can choose what layers to combine based on our purpose. A GIS is most often associated with maps. A map, however, is only one of three ways a GIS can be used to work with geographic information. These three ways are: The Database View A GIS is a unique kind of database of the world - a geographic database (geodatabase). It is an "Information System for Geography". Fundamentally, a GIS is based on a structured database that describes the world in geographic terms.

The Map View: A GIS is a set of intelligent maps and other views that show features and feature relationships on the Earth's surface. Maps of the underlying geographic information can be constructed and used as "windows into the database" to support queries, analysis, and editing of the information. This is called geovisualization. The Model View: A GIS is a set of information transformation tools that derive new geographic datasets from existing datasets. These geo-processing functions take information from existing datasets, apply analytic functions, and write results into new derived datasets. Together, these three views are critical parts of a Geographical Information System and are used at varying levels in all GIS applications. To illustrate the application of a GIS, think about the information that an environmental scientist would need to study landslide hazards in a area. A GIS of the area would contain layers that represent the topography, soil type and land cover and these could be used to derive slope information, direction of water flow, soil stability, and the potential for landslides. The final result of the analysis can then be displayed in a map or interactive 3D terrain model. This type of information could never before be derived from maps that were printed onto paper.

Fig 9. a. A land slips under investigation using GPS and GIS. b. GPS data covering the land slip loaded into the GIS and a map of the slope over the land slip, darker colors indicate steeper slopes. Application of GIS in Mining

• Land Ownership and Mineral Claims • Exploration Management • Siting of ore pass, draw points, ramps, shaft, winze, raises, haulways that are within a certain

distance of production centers (stopes) and meeting production criteria. • Querying the production stopes affected by unstable ground conditions, hazardous gas,

refractory ore, etc. • In mine development, GIS can assist the planners in establishing the optimal location for

exploration drifts, crosscuts, sublevels, man ways, ventilation shafts • Transport routes: mine planners utilize GIS in combination with remote sensing to plan the

best alternative for transportation of goods and supplies to and from the nearest community to the mine site. Integrating thematic layers such as topography, land ownership, land-use, population, geotechnical, and climate can facilitate the objective selection of the economically and environmentally preferable alternative.

• Natural hazards: GIS and remote sensing assist the planners in identifying natural hazards such as potential landslides, floods, earthquakes, and volcanic eruptions prior to the construction of production and housing installations.

• Population distribution: planners of a new mine may need information on population density, socio-economic distribution, labor resources, housing, and recreational infrastructure in the preparation of the environmental impact assessment.

• Selection of sites for housing and dumps: use GIS capabilities for the selection of a housing site that meets safety, scenic, and recreational requirement within reasonable proximity to the mining operation. Topographic, vegetation, drainage, and soils coverages together with concentration of toxic substances are incorporated in the analysis.

Photogrammetry and Remote Sensing Remote sensing and photogrammetry are exciting active fields of research and provide a wide range of interesting applications. Developments in satellite and sensor technology have made it possible to detect objects as small as one meter from satellites, and airborne sensors can even provide more detailed spatial information about the Earth surface. Images acquired by satellite and airborne sensors are processed and analyzed and used as data sources in a GIS for further analysis or visualization. Remote sensing is the science of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.

Fig. 10. a. A LANDSAT - pixel resolution of 30m b. Sensors, GIS plots Remote sensing imagery can provide a valuable source of information for mapping the Earth surface. Satellite images have made it possible to map at global to regional scales, to map remote areas, and to update existing information efficiently and cheaply. Advances in spatial resolution now allow us to detect small objects from both airborne sensors and satellite sensors. Additionally, the increase in spectral resolution of multi-spectral and hyper-spectral sensors has made it possible to derive information on the physical composition of the surface, such as chemical components in vegetation, soil, rock and water. This makes remote sensing data suitable for a range of applications, like land cover mapping, geology, botany, forestry, biology, urban planning, and oceanography. Photogrammetry is the science of obtaining reliable measurements and maps from photographs. So photogrammetry is a special type of remote sensing. Sometimes the photographs are taken using very expensive, accurate and large film cameras mounted in aircraft; sometimes they are taken using inexpensive hand held cameras. Nowadays digital cameras are often used instead of film cameras. Photogrammetrists use aerial cameras to photograph the Earth and produce topographic maps. Terrestrial photogrammetry is also used to measure large structures such as dams, moving objects such as manufactured parts on a production line, or objects that are in dangerous or inaccessible environments such as the subsidence in mining areas.

Smart Stations It is a total station with integrated GPS receivers. All commands, displays, functions, operations and computations relating to GPS reside in the total station. With smartstation there is no need to setup control points, long traverses or resections. Just Smart Station is set up at chosen point and GPS determine the position. The survey work becomes easier, quicker and it needs only few setups. Total stations need local control points over which they can be set up, from which they can traverse, and to which they can measure to resect their positions. On the other hand, GPS receivers can determine their positions within a few seconds to centimeter-level accuracy using data from GPS reference stations that may be 50km or more away. GPS rover receivers are fast and efficient to use but need an open view of the sky in order that they can receive the satellite signals. They are at their most advantageous in wide, open areas. By contrast, total stations can measure and stakeout where GPS cannot be used: underground, to points under trees and bushes, in city canyons, on construction sites where there are large obstructions. Total stations and GPS RTK equipment each have their advantages. Smart- Station combines the best of both.

Fig. 11. Smartstation (Leica)

3. SOFTWARE SURPAC VISION FOR MINE SURVEYING

Surpac Vision Surpac Vision had its beginnings as a package for Surveyors, and has subsequently secured its position as a useful computer package for surveyors and other mining professionals. Surpac Vision combines great flexibility as well as functionality to maintain client satisfaction in surveying tools. The powerful 3D visualization, editing and file manipulation tools available in Surpac make it versatile Survey Station Database The Surpac Vision survey database is used to store and manage all survey station and stability monitoring information. There are interfaces to all popular data recorders to enable rapid down loading and up loading of data and therefore rapid processing of survey information.

Setout tools Many tools exist in Surpac Vision to assist the Surveyor in producing setout information for surface and underground mine design, roadways, boundary’s, mine grade control and any other feature that may have been created or loaded into the system. Tools for changing co-ordinate systems, calculating grades, intersecting surface models (DTM’s) and producing detailed plans allow the Surveyor to carry out his duties in a professional and informative manor.

Fig. 12 Opencast mine plan using Surpac Vision software Volume Calculations Surpac Vision can calculate volumes using a variety of techniques, thus allowing results to be audited. Surface or digital terrain models are one method used for volume calculation and have a particularly rigorous model creation routine to ensure accuracy and consistency in volumes. The reporting of bench by bench and cut and fill volumes is easily achieved. Volume reports can be plotted as a table on plots of the surveyed area for hard copy graphical representation or printed directly to a printer. Powerful 3D visualization tools allow coloring and lighting of surfaces and assist with error checking and presentation of results. Underground The survey database supports traditional survey techniques for entering new stations from underground survey traversing. Chain and offset surveys can be entered easily, as can radiation surveys to create floor and back (roof) strings. The data is readily viewed and edited in the Graphics module of Surpac Vision. Wire framing of underground workings is a powerful but straightforward procedure using the advanced solid modeling tools in Surpac Vision. The 3D models produced can be colored and displayed with different lighting effects as a powerful aid for surveyors to gain understanding of the underground mine layout. These 3D models can be used by other professionals such as Geologists and Mining engineers for further design, evaluation and reporting. The seamless transferring of data between disciplines is a feature of Surpac Vision ensures easier communication and sharing of data between departments. Survey Control Adjustment Surpac Vision uses the Least Squares Adjustment method for network adjustments. When using the Least Squares Adjustment method up to 100 stations may be adjusted with the results being written to a file or directly to the database. A full report providing information on all adjustment parameters and errors is produced for further checking.

Stability Monitoring The Surpac Vision Survey database supports time dependent data such as that obtained in Stability monitoring. Survey information such as prism movements may be down loaded and processed in minutes to produce customized graphs depicting such elements as cumulative movement, velocity and acceleration. This allows early warning of movement trends and maintains an audit trail of the stability monitoring. REFERENCES 1. Venkateshwar, A. Scope for application of GPS in Indian Coal Industry,

http://www.gisdevelopment.net/application/geology/mineral/geom0011.htm 2. http://www.leica-geosystems.com/corporate/en/ndef/lgs_4521.htm 3. http://www.trimble.com/trimbleS6.shtml 4. http://www.topcon.co.uk/index.asp?pageid=05fa10881fd449a29592ae739c678204 5. http://www.leica-geosystems.com/corporate/en/products/levels/lgs_4453.htm 6. http://www.leica-geosystems.com/corporate/en/products/levels/lgs_5284.htm 7. http://www.surpac.com/products/coal/index.shtml 8. http://www.surpac.com/products/coal/minex/images/a_brown%20mine%20640.gif 9. www.3dlasermapping.com/mining.htm 10. www.surveyors.org.au 11. http://www.hammond.swayne.com