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Laser Scanning - New Dimension in Mine Surveying.

Nikolaus Studnicka
Manager International Sales
RIEGL Laser Measurement Systems,
Email: nstudnicka@riegl.co.at

Introduction to Laser Scanning:

Till date theodolites and total stations has been the first choice for the surveyors.

A laser-scanning instrument works on the principle of LIDAR (Light Detection & Radar). The scanner emits laser rays, which hits the object to be captured and comes back to the scanner. The scanner consists of a emitter and receiver. Depending upon the total traveling time the scanner calculates the point distance in X, Y & Z. Laser scanner enables the surveyor to collect the data at lightning fast speed with accurate 3D survey data. Within a very short period of time the scanner collects billions of points (point-cloud), this point cloud data can be used to create 3D models for a wide variety of spatial and volumetric tasks.

Advantages of using Riegl Laser Scanners in Mines

a) Data acquisition is much faster than manual data capturing process. A Riegl Scanner measures upto 120000 pts/sec where as a total station can captures one point at a time.

b) Faster data acquisition leads to shorter project cycle, which leads to significant amount of cost & time savings. A single surveyor can carry out the entire job.

c) Collection of additional measurements for futures use

d) Ability to capture data of hazardous area, which are physically inaccessible. In addition to this the scanner can capture data without disrupting the ongoing work.

e) Inspite of the poor reflectivity of coal the scanner can reach upto a distance of 700 m at one stretch.

Why Riegl?

Produce 3-Dimensional images that are accurate within a few millimeters
Record hundreds of thousands (even millions!) of spatial points in minutes

Measure precise dimensions of a scanned feature from a modeled image

Scan areas at any time of day or night, under any lighting conditions

Superimpose elevation contours (of any interval) over captured data

Superimpose reference grids (of any interval) over captured data

Tie spatial reference points to an established coordinate system

Take scans from one or more locations and elevations

Rotate around a 3D image from any vantage point

Connect multiple scans to cover an extensive area

How Riegl LMS Z-420i technology works?

Just like an EDM or a Digital Theodolite, Riegl is a portable, tripod-mounted system. However, Riegl uses a infrared laser in conjunction with an integrated digital camera and a Windows-based PC notebook computer in the field. The range finder electronics of the scanner is optimized to meet the requirements of high speed scanning (fast laser repetition rate, fast signal processing, and high speed data interface). The vertical deflection (¡§line scan¡¨) of the laser beam is realized by a polygon with a number of reflective surfaces. For high scanning rates and/or a vertical scan angle „¹ upto 80„H, the polygonal mirror rotates continuously at adjustable speed. For slow scanning rates and/or small scanning angles , it is oscillating linearly up and down. The horizontal scan (¡§frame scan¡¨) is provided by rotating the complete optical head up to 360„H.

The gained information: RANGE, ANGLE and SIGNAL AMPLITUDE, is provided via TCP/IP Ethernet interface or parallel data output which can be connected directly to the ECP compatible LPT Printer port of a laptop running the Riegl Riscan Pro Software

The Riegl laser can scan at a speed of up to 120000 points per second, making it an extremely rapid data collection tool. The scanner does not require leveling prior to scanning an area, which means it can be placed in any location. It also does not have lighting requirements.

The raw point cloud data can then be ¡§shrink wrapped¡¨ to further enhance the image. Just like laying a blanket over the cloud of reference points, the shrink wrap process fills in the spaces between the points in the cloud, producing smooth, multicolored surfaces. The data from the Riegl scan may be used without enhancement, or it can be exported to Computer-Aided Design (CAD) software for further processing. Depending on the project goals, CAD software can be used to enhance the image to produce a 3D model complete with shadowing, accurate colors, and even landscape backgrounds that would allow an individual to experience a virtual ¡§fly-through¡¨ of a resource such as a mine, a cave, or a landscape.

A single scan can be integrated (or ¡§registered¡¨) with other scans to show a larger area. This feature allows excavators at an archaeological site, for example, to tie together horizontal data layers between adjacent excavation units. It also means that data may be tied together at a later date, allowing flexibility in a project¡¦s schedule and resources