National Transformation Version 2
                 =================================
  
                           Readme File
                               for
                      Contour Sub-Directory
  
  
  
  
  Contour Plots of Grid Shift File Data
  -------------------------------------
  
  The contour plots show the four types of data contained in the
  grid shift file: shift in latitude, shift in longitude,
  accuracy of latitude shift, and accuracy of longitude shift.
  These plots are useful to visualize the magnitudes and
  variations of the shifts in the area of application, and to
  obtain an impression of the accuracy of the shifts. They
  provide a broad picture that bridges the gap between sampling
  a few points and printing out the entire grid shift table for
  an area.
  
  A small scale view shows the whole country with contours at 10
  metre intervals. There are four medium scale views covering
  each of the four base grid areas, with contour intervals of 5
  metres. Large scale views cover eleven smaller areas based on
  groups of NTS mapsheets, with contour intervals of 1 metre. In
  total there are 16 views, with four data types per view, for a
  total of 64 different plots.
  
  The NTS mapsheets covered by each of the eleven large scale
  views are:
  
      area01          NTS 20/21/30/31/40/41
      area02          NTS 1/10/11/20E/21E
      area03          NTS 2/3/12/13/22E/23E
      area04          NTS 22/23/32/33/42/43
      area05          NTS 52/53/62/63/72/73
      area06          NTS 82/83/92/93/102/103
      area07          NTS 84/85/94/95/104/105/114/115
      area08          NTS 44/45/54/55/64/65/74/75
      area09          NTS 14/15/24/25/34/35
      area10          NTS 16/26/27/36/37/46/47/56/57
      area11          NTS 66/67/76/77/86/87/96/97/
                          106/107/116/117
  
  An index graphic (contour.gif) outlines and identifies the
  eleven large scale views. The index graphic of the base grid
  sub-files (basegrid.gif) also serves as an index to the medium
  scale plots.
  
  The plots were created in PostScript format using PVWave
  graphics software. The colour shading is based on a rainbow
  palette, ranging from blue to red. 4-bit colour (16 colours)
  was used to accommodate viewing on systems with basic video
  capabilities. A range from -160 metres to +160 metres was
  selected for the coordinate shifts, and from 0 metres to +2
  metres for the accuracies of the shifts. These ranges were
  applied consistently for all views, providing a standard
  colour reference. Any data falling outside of these ranges
  shows as white.
  
  The GIF files were produced by using ImageMagick to convert
  the PostScript files that were output from PVWave. To assist
  users who do not have access to a colour printer, the contour
  plots of the shifts were also produced in black and white
  without shading, and are included in PostScript format only.
  The accuracy plots were not produced in black and white, since
  the accuracies are depicted by colour shading only, with no
  contour lines.
  
  
  Contour Plots - Filenames and Directories
  -----------------------------------------
  
  Each of the 16 views has its own directory which contains all
  of the plot files for that view. The GIF files are at the main
  level of the directory, while the colour PostScript files are
  in a sub-directory named ps_col, and the black and white
  PostScript files are in a sub-directory named ps_bw.
  
  The data types for each view have standard file names as
  follows:
  
      ***latsh        Latitude Shift for view ***
  
      ***lonsh        Longitude Shift for view ***
  
      ***latsd        Accuracy of Latitude Shift for view ***
  
      ***lonsd        Accuracy of Longitude Shift for view ***
  
  
  
  The directory for each view appears as follows:
  
  
      \viewname         ***latsh.gif
                        ***lonsh.gif
                        ***latsd.gif
                        ***lonsd.gif
  
                        \ps_bw            ***latsh.ps
                                          ***lonsh.ps
  
                        \ps_col           ***latsh.ps
                                          ***lonsh.ps
                                          ***latsd.ps
                                          ***lonsd.ps
  
  
  There is a directory for the small scale view covering all of
  Canada, a directory for the medium scale views, and a
  directory for the large scale views. They appear as follows:
  
  
     \graphics      \contour       \canada
  
                                   \basegrid      basegrid.gif
                                                  basegrid.ps
                                                  \caarctic
                                                  \caeast
                                                  \canorth
                                                  \cawest
  
                                   \ntsareas      contour.gif
                                                  contour.ps
                                                  \area01
                                                  \area02
                                                  \area03
                                                  \area04
                                                  \area05
                                                  \area06
                                                  \area07
                                                  \area08
                                                  \area09
                                                  \area10
                                                  \area11
  
  
  
  
  --- End of Readme File ---