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Further notes on the SAMPLER program

It is useful to note one or two further facts about the SAMPLER. First, the digitised data in the boundary and contour files is not stored in memory, though the subsampled values are. This means that the size of the DIGIT format files is not limited by the memory available. Secondly, the SAMPLER, in common with the other interactive graphics programs, has provision for windowing ( option {TOP}DISPLAY ) which you may want to experiment with at this stage (see Chapter gif for full information on DISPLAY).

The option of using different colours for nodes or digitised data is available via the coloured bars shown in the right hand panel. For example, when {TOP}BOUNDARY is picked, there is a coloured area beside the logo 'Boundary Line Colour'. Picking on the this coloured patch with the mouse will change the colour used to display the digitised boundary data. Any one of the 16 colours available in GKS can be chosen by repeated picking. In particular, in the rare event that display of the digitiised data needs to be temporarily suppressed, one can plot it invisibly in background colour, which is one of the 16 options.

Note that the last option in the right hand panel for {TOP}BOUNDARY, whose full logo is 'Check boundary orientation' is not yet reliable. When perfected, this option will provide an error message if the outer boundary has been digitised clockwise or an island has been digitised counterclockwise. However, if both the outer boundary and all the islands have been digitised in reverse order, that is, outer boundary clockwise and islands counterclockwise, the triangulation program, GRIDIT, used next, will still function correctly.

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