Space Diag Scan:

Location:

Each parameter system (for X and Y) has a variable flag that signals if the current value is equal to the minimum value, the maximum value -or is between these values:

The values for these flags are:

Minimum => 1
Between => 0
Maximum => 2

Each location within the (2-dimensional) scanning area can thus be identified in terms of combinations of the values of these two flags.

                I.e. Minimum, Maximum   (1,2) => Bottom left corner
                       Between, Between      (0,0) => Central area
                   Between, Minimum     (0,1) => Top Horizontal Edge

Dealing with two numbers is rather awkward

--so we map them into a single number using the formula:

Code = (3 x Y-flag) + X-flag:

i.e.   X-flag => 0 1 2 0 1 2 0 1 2
      3 x Y-flag => 0 0 0 3 3 3 6 6 6
                               ---------------------------   +
                                0 1 2 3 4 5 6 7 8              =>    Location Code
                               ---------------------------

Direction:

The direction of the scan is controlled by incrementing the current (2-dimensional) position by a constant step (the size of the cells contained within the area). The size of the step can be variable -if one
multiplies it by -1, 0, +1 -which actually defines the direction of the increment -and thus (when both parameters are paired) the direction within a 2-dimensional area.

i.e. X Y
    -1, -1    => Diagonal towards Bottom left corner
          0, 0     => No movement
          0, -1    => Vertical upward movement

Note: Movement is relative to Locations -but the coding is different:
                So we map (convert) the direction data :

   -1 => 1
   0 => 0
   +1 => 2

                and then code the result (for X and Y) in the same way as the Location code

                     (see diagram above)

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click on relevant image to link to notes or Java programmes

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Creating A Space For Change
Data Space
Klee index

Trevor Batten
Baclayon 2011
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Space Diag Scan -Information Coding:

Making the codes: