GENERAL                       

Project                       Lefroy
Survey area                   Lefroy-West
Located data type             0.1 Second Final Data

Surveyed by                   GPX AIRBORNE PTY LTD.
Job number                    Lefroy
Processed by                  GPX AIRBORNE PTY LTD.
Creation date                 June 2007

SURVEY SPECIFICATIONS         

Survey flown                  March - April 2007
Traverse line spacing         100 metres
Traverse line direction       000-180 degrees
Tie line spacing              1000 metres
Tie line direction            090-270 degrees

Survey height                 90 metres

LOCATED DATA FORMAT           

Variable                      Units          Undefined      From  To    Format    

Line number                                  9999999        1     8     I8        
Easting (MGA55)               metres         9999999.99     9     19    F11.2     
Northing (MGA55)              metres         9999999.99     20    30    F11.2     
Fiducial                                     99999.99       31    39    F9.2      
Flight number                                999            40    43    I4        
Direction (1=E, 2=N, 3=W, 4=S)               9              44    45    I2        
Date (YYYYMMDD)                              99999999       46    54    I9        
Time (GPS)                    seconds        99999.99       55    63    F9.2      
Longitude (GDA94)             degrees        999.999999     64    74    F11.6     
Latitude (GDA94)              degrees        999.999999     75    85    F11.6     
Radar altimeter               metres         9999.9         86    92    F7.1      
GPS altitude                  metres         9999.9         93    99    F7.1      
Raw magnetics                 nT             99999.999      100   109   F10.3     
Post compensated magnetics    nT             99999.999      110   119   F10.3     
Diurnal                       nT             99999.999      120   129   F10.3     
Final magnetics               nT             99999.999      130   139   F10.3     
Pressure                      millibars      9999.9         140   146   F7.1      
Temperature                   degrees C      99.9           147   151   F5.1      
Raw total count               cps            999999         152   158   F7.0      
Raw potassium                 cps            9999           159   163   F5.0      
Raw uranium                   cps            9999           164   168   F5.0      
Raw thorium                   cps            9999           169   173   F5.0      
Raw cosmic                    cps            9999           174   178   F5.0      
Final total count             cps            99999.99       179   187   F9.2      
Final potassium               cps            99999.99       188   196   F9.2      
Final uranium                 cps            99999.99       197   205   F9.2      
Final thorium                 cps            99999.99       206   214   F9.2      
Final DTM                     metres         99999.9        215   222   F8.1      

DATA PROCESSING               

COORDINATE DATA               
All lines are scissored to the following rules:                            
  1) A 'smooth' edge outside the area boundary.                            
  2) Maximum line overlap of 0 fiducials within                            
     the area boundary.                                                    

The local projection is a UTM projection based on the                      
GDA94 spheroid with a central meridian of 147 East degrees.                
System parallax of 0.6 fiducial has been removed.                          

MAGNETIC DATA                 
The magnetic data has been corrected for regional gradient by subtraction  
of IGRF model 2005 computed continuously over the whole area based on      
the GPS height.                                                            
Diurnal magnetic variations have been removed.                             
System parallax of 1.6 fiducial has been removed.                          
Tie-line levelling has been applied.                                       
Microlevelling has been applied.                                           
A base value of 61320 nT has been added to the data.                       

RADIOMETRIC DATA              

Raw channel data provided has been energy calibrated                       
NASVD has been applied to channel data prior to windowing                  
System parallax of 0.0 fiducial has been removed.                          
Height attenuated to 90m AGL                                               
Airborne radon has been removed                                            

AIRCRAFT BACKGROUND                                UNITS
Total Count                           81.67          cps
Potassium                             23.35          cps
Uranium                                0.59          cps
Thorium                                0.67          cps
COSMIC STRIPPING RATIOS       
Total Count                        0.811201             
Potassium                          0.044663             
Uranium                            0.038646             
Thorium                            0.043791             
COMPTON STRIPPING RATIOS      
alpha                                 0.250             
beta                                  0.400             
gamma                                 0.810             
a                                     0.060             
HEIGHT ATTENUATION COEFFICIENT
Total Count                        0.006928    per metre
Potassium                          0.009043    per metre
Uranium                            0.007186    per metre
Thorium                            0.006892    per metre
WINDOW ENERGY LEVELS             Low Energy High Energy
Total Count                           410.0      2810.0          keV
Potassium                            1370.0      1570.0          keV
Uranium                              1660.0      1860.0          keV
Thorium                              2410.0      2810.0          keV

DIGITAL TERRAIN MODEL DATA    

DIGITAL TERRAIN MODEL CALCULATION                                          
The radar altimeter data was subtracted from the GPS heights to provide    
a digital elevation model which is height above the WGS84 spheroid. Using  
interpolation on the 120 second DMA Geoid model, a correction was computed 
and subtracted from the WGS84 data to convert to height above the geoid.   

DATA RELIABILITY              
This Digital Terrain Model (DTM) has been computed from data generated     
during the course of an airborne geophysical survey flown at a nominal     
spacing of 100m and data has been interpolated between such lines.         
Every effort has been made to make this model a useful general reference.  
No guarantee can be made that this model is a true representation of height
above sea level as it can contain radar altimeter responses from buildings 
and in some instances dense timber. Users of the product should be aware   
of the topographic limitations mapped herewithin. Do not use this DTM for  
navigation purposes.                                                       

