THE 3D MAPPING OF A TEXTURED SURFACE USING DIGITAL PHOTOGRAMMETRIC TECHNIQUES 
J.L. Smit!, H. Rüther! and E. Siebrits? 
! Department of Surveying and Geodetic Engineering 
University of Cape Town, Rondebosch, 7700, South Africa 
Phone: +27-21 650-3577; Fax: +27-21-650 3572 
Internet: lloyd@engfac.uct.ac.za 
ruther@engfac.uct.ac.za 
? Stimulation Engineering Applications 
Schlumberger Dowell, Inc. 
P.O. Box 2710, Tulsa, OK 74101, U.S.A. 
Phone: +91-918-250 4296; Fax: +91-918-250 9323 
Internet: siebrits@tulsa.dowell.slb.com 
KEY WORDS: Digital Photogrammetry, Matching, Edge Detection, Deformation Analysis, Underground Mining. 
ABSTRACT: 
The determination of three-dimensional (XYZ) co-ordinates of a textured surface, represented by densely spaced individual points, 
by means of digital photogrammetric techniques, is reported. The method is applied to the measurement of the three-dimensional 
changes that occur on the rock face in a deep-level underground mine, due to a pre-conditioning blast. Digital Photogrammetric 
techniques applied are discussed and a sample of the results is presented. The sub-millimetre accuracies required for the deformation 
analysis were achieved. 
1. INTRODUCTION and constrained, the typical working area is not higher than 
0.5m to 1m and thus provides a good opportunity to 
The deep-level gold mines on the Witwatersrand (South demonstrate the flexibility and accuracy of digital 
Africa) are located at depths of over 3,000 m below surface. photogrammetry in restrictive environments. This paper 
The gold ore is located in extensive tabular reefs, kilometres provides a brief description of the procedures followed in 
in extent, but only a few centimetres thick. Mining obtaining the desired measurements of the rock face to be 
excavations are thus also tabular, hundreds of metres in evaluated and presents a sample of the results achieved in this 
extent, and less than 1 metre in height. The tabular shape of regard. 
these excavations or panels, plus the large overburden, result 
in extensive mining induced stress changes in the rock mass In order to generate the three dimensional (XYZ) object space 
surrounding them. With each advance of the mine face, co-ordinates for the points of interest, which represent the 
sudden changes in the rock stresses occur. This results in surface to be mapped, the following steps were taken: 
sudden fracturing of the exposed surfaces of the excavation, 
with accompanied deformation. In some mining panels, it is - Establishment of a Reference System 
desirable to "pre-condition" or soften the rock mass ahead of 
the face by pre-fracturing it with large blasts. This has the - Image Acquisition 
effect of pushing the critical stress field deeper into the rock 
mass, alleviating some of the fracturing and hazardous - Camera Position Location 
deformations in the vicinity of the excavation. 
- Feature Extraction 
From a research perspective, it is desirable to quantify the 
deformations of the face due to blasts in order to better - Image Matching 
understand their effect on the fracture patterns that develop. 
Digital photogrammetry is an ideal method that can be - Space Intersection 
employed to monitor these deformations. The necessary 
photogrammetric equipment is portable and easy to use - Deformation Analysis 
underground, where conditions are extreme with 
temperatures as high as 40 deg C and humidity close to 100 The details of each of these procedures are discussed in the 
percent. Digital photogrammetric techniques are highly following. 
accurate, and can be used to detect quite small 
three-dimensional changes. Furthermore, a digital elevation 
model, of the new fractures that develop on the face due to a 2. REFERENCE CO-ORDINATE SYSTEM 
blast, can be produced as part of the photogrammetric 
process. As in all deformation surveys, the maintenance of a reference 
co-ordinate system for the duration of the survey is 
The underground mining environment is especially hazardous paramount. Due to the nature of the underground mining 
728 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996