TRYPHINE DUDZAYI

 Surveying instrumentation has undergone a major transformation over the past years transit to the modern instruments.  The theodolite, steel tape, and field book have in many cases been replaced by electronic field instrumentation such as the EDM, GPS, hand- held data collectors, automatic laser levels, total station and 3D scanners.  However this presentation will be centred on 3D Laser Scanners

 It is a device that analysis the real object or environment in its original shape by taking numerous shots that instantly create a well detailed profile pickup.

 Laser scanners used in mine surveying use a time of flight measuring principle which similar in concept to other electronic distance measurement equipment but designed and built using technologies allowing measurement at extreme high repetition rates at very long ranges without the use of reflectors.

 Pit pickups,  Stockpile volume measurement,  Slime dam survey,  Structural measurement of plant items  Face mapping for geological and geotechnical detail  Pre and post blast measurements to determine blast performance  Open stope surveys  Development drive mapping and section measurement to compare and confirm against design  It allows users to extract sections, contours, breakline, volumentric and more information from the detailed scan data much faster than by any other survey techniques

 One of the first things a surveyor asks about 3D laser scanning is “what do I do with all those points,” or, “why do I need all those points.” Dealing with a point cloud containing millions instead of a few hundred specially selected points for a site survey does cause some to ponder. The good news is: It’s good news. Point cloud data gives the surveyor more control of the job site -- common surveying functions such as topographic mapping can be done quickly and efficiently, and with more confidence than ever before. Here are just a few examples of how a point cloud can be quickly utilized to produce a variety of deliverables:

 Work with the raw point cloud in AutoCAD, Micro Station, or other CAD software, create a 2D or 3D drawing.  Extract feature codes directly from point cloud, export to feature code processing software.  Calculate volumes or surface areas directly from the point cloud.  Create a DTM, generate contours of a selected area automatically.  Export DTM points to 3rd party contour package.  Measure between any points in the point cloud, including elevation differences, slope, or horizontal distance.

 Scanning a site captures everything in the selected field-of-view, including ground points, traffic signs, road surface, telephone poles, fences, etc. Depending on the requested deliverable, these features are highly relevant to the surveyor. However, because the scanner blankets the entire site, undesired objects are also collected, including people, vegetation, trees, traffic, parked cars, etc

. As traditional surveys do not typically include such “noise,” this is a step in the process that is new to the surveyor. Fortunately, due to recent major advances in point cloud processing software; powerful tools have emerged to allow the surveyor to quickly and easily eliminate noise. An automated process called “region grow "utilizes algorithms that “crawl” across contiguous surfaces to parse out the noise from the surface.

 Diagram below shows the volume of a hazardous pit as derived from a single scan of the site. In this calculation, the user can define a geometric plane to which the volume measurements are made, for example, a plane that represents the top of the pit or the existing grade at the base of a landfill. It is also possible to make measurements from a specified elevation.

 Once this reference plane is established, a sampling rate is selected that indicates the density of the“virtual rod readings” made relative to the reference plane. Based on this information, the volume is displayed in the desired units. With 3D laser scanning, field-to-finish volume calculations are possible in a matter of minutes, compared to several hours with traditional methods. In addition, the amount of detail generated by thousands of survey-grade points yields a more accurate representation of the earth’s surface.

 One of the most common objective for an engineering survey is a topographic map that depicts planimetric features, legal boundaries, objects of interest, and contours of the terrain.

 Greater accuracy in measurement of stockpiles,  Greater accuracy in pit volumes,  Greater accuracy in volume measurement of underground excavations,  Faster measurement of stockpiles,  Faster measurement of underground excavations,  Less labour is required in the measurement process. Thus labour can be channelled to other projects.

In conclusion I would recommend that a 3D scanner be used in all tacheometric work, because apart from its high price when compared to most total stations it offers the following benefits:-  More detailed topography,  Higher productivity, lower costs for certain projects,  Improved safety,

 Reduced errors in data capture,  Reduced errors due to omission,  Ability to “return to the site” without leaving the office,  It provides a detailed, reliable, and accurate solution to many surveying and measurement problems.

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