Determination of rock types by spectral scanning

Abstract

Described herein is a method and system for classifying rock types in a rock body. The method comprises the steps of obtaining spectral data from a spectral measurement ( 202 ) of a surface region of the rock body and then determining a first spectral ratio between two wavelength bands of the spectral data. From the first spectral ratio it can be assessed ( 204 ) whether the measurement is a high-angle measurement, and if the measurement is not a high-angle measurement then a further spectral ratio between two further wavelength bands of the spectral data is determined ( 208 ). The further spectral ratio is then compared ( 210 ) with a corresponding diagnostic criterion to assess whether the surface region comprises a first rock type associated with the further spectral ratio and diagnostic criterion.

1 . A method of identifying rock types in a rock body, comprising
 scanning a surface of the rock body with a spectral sensor to obtain spectral data from the rock body surface, said spectral data comprising multiple spectra obtained from successively scanned regions of the rock body surface;   determining for different spectra a spectral parameter indicative of spectra derived from high angle reflectance; and   using data from the spectra so determined not to be derived from high angle reflectance to determine rock types present at said regions of the rock body surface.   
     
     
         2 . A method as claimed in  claim 1 , wherein said parameter is a ratio derived from a comparison of the spectral data at differing specific wavelength bands. 
     
     
         3 . A method as claimed in  claim 2 , wherein rock types are determined from the spectral data of spectra determined not to be from high angle reflectance by determining for each of those spectra a plurality of further spectral ratios each derived from a comparison of spectral data at differing specific wavelength bands as indicators of differing rock types. 
     
     
         4 . A method as claimed in  claim 2 , wherein the spectral ratios indicative of rock types are determined from spectral data at wavelength bands which are not affected by atmospheric absorptions under natural light illumination. 
     
     
         5 . A method of identifying rock types in a rock body, comprising scanning a surface of a rock body with a spectral sensor to obtain spectral data from the rock body surface, said data comprising multiple spectra obtained from successively scanned regions of the rock body surface; and
 determining for differing spectra a plurality of spectral ratios each determined from a comparison of the spectral data at differing specific wavelength bands as indicators of differing rock types.   
     
     
         6 . A method as claimed in  claim 5 , wherein the spectral ratios are determined from spectral data at wavelength bands which are not affected by atmospheric absorption under natural light illumination. 
     
     
         7 . A method as claimed in  claim 1  or  claim 5  in which the rock body is a mineable rock body in a mine and the method is used to make ore grade assessments of the rock body for mining. 
     
     
         8 . A method of mining comprising scanning a mine bench face with a spectral sensor to obtain spectral data from a rock body at the bench face, said data comprising multiple spectra obtained from successively scanned regions of the rock body surface;
 determining for different spectra a spectral parameter indicative of spectra derived from high angle reflectance;   using data from the spectra so determined not to be derived from high angle reflectance to determine rock types at said regions of the rock body surface;   removing material from the bench; and   transporting removed material for processing in accordance with the rock type determination derived from the bench face.   
     
     
         9 . A method as claimed in  claim 8 , wherein said parameter is a ratio determined from a comparison of the spectral data at differing wavelength bands. 
     
     
         10 . A method as claimed in  claim 9 , wherein rock types are determined from the spectral data of spectra determined not to be from high angle reflectance by determining for each of those spectra a plurality of further spectral ratios each derived from a comparison of spectral data at differing specific wavelength bands as indicators of differing rock types. 
     
     
         11 . A method of mining comprising
 scanning a mine bench face with a spectral sensor to obtain spectral data from a rock body at the bench face, said data comprising multiple spectra obtained from successively scanned regions of the rock body surface;   determining for different spectra a plurality of spectral ratios each derived from a comparison of spectral data at differing specific wavelength bands as indicators of differing rock types;   removing material from the bench; and   transporting removed material for processing in accordance with the rock type determinations.   
     
     
         12 . A method as claimed in  claim 11 , wherein the spectral ratios are determined from spectral data at wavelength bands which are not affected by atmospheric absorption under natural light illumination. 
     
     
         13 . A method as claimed in  claim 1 ,  5 ,  8  or  11  wherein the spectra include spectra in the Visible Near Infrared Range (VNIR). 
     
     
         14 . A method as claimed in  claim 1 ,  5 ,  8  or  11  wherein the spectra include spectra in the Short Wave Infrared Range (SWIR). 
     
     
         15 . A method as claimed in  claim 1 ,  5 ,  8  or  11  wherein the spectral data comprise reflectance values at differing wavelengths through the spectra. 
     
     
         16 . A method for classifying rock types in a rock body comprising:
 obtaining spectral data from a spectral measurement of a surface region of the rock body;   determining a first spectral ratio between two wavelength bands of the spectral data;   assessing from the first spectral ratio whether the measurement is a high-angle measurement;   if the measurement is not a high-angle measurement, determining a further spectral ratio between two further wavelength bands of the spectral data; and   comparing the further spectral ratio with a corresponding diagnostic criterion to assess whether the surface region comprises a first rock type associated with the further spectral ratio and diagnostic criterion.   
     
     
         17 . The method of  claim 16  comprising
 determining a plurality of further spectral ratios between respective wavelength bands of the spectral data; and 
 sequentially comparing the plurality of further spectral ratios with corresponding diagnostic criteria to classify a rock type of the surface region. 
 
     
     
         18 . The method of  claim 16  wherein the measurement is assessed to be a high-angle measurement if the first spectral ratio exceeds an edge anomaly threshold. 
     
     
         19 . A system for classifying rock types in a rock body comprising:
 a spectral sensor for obtaining spectral data from a surface region of the rock body; and   a processor for analysing the spectral data, wherein the processor is programmed to perform a method of:   determining a first spectral ratio between two wavelength bands of the spectral data;   assessing from the first spectral ratio whether the measurement is a high angle measurement;   if the measurement is not a high angle measurement, determining a further spectral ratio between two further wavelength bands of the spectral data; and   comparing the further spectral ratio with a corresponding diagnostic criterion to assess whether the surface region comprises a first rock type associated with the further spectral ratio and diagnostic criterion.   
     
     
         20 . A computer program product comprising machine-readable instructions recorded on a recording medium, for controlling the operation of a data processing apparatus to perform a method for classifying rock types in a rock body comprising:
 obtaining spectral data from a spectral measurement of a surface region of the rock body;   determining a first spectral ratio between two wavelength bands of the spectral data;   assessing from the first spectral ratio whether the measurement is a high-angle measurement;   if the measurement is not a high-angle measurement, determining a further spectral ratio between two further wavelength bands of the spectral data; and   comparing the further spectral ratio with a corresponding diagnostic criterion to assess whether the surface region comprises a first rock type associated with the further spectral ratio and diagnostic criterion.