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Definition of the optional ordinal value that will always keep the same colour when the class break colours are rescaled in the grid display. After rescaling, the highest lowerValue will be changed to the maximum grid value visible in the current zoom extent and the lowest lowerValue will be changed to the minimum grid value visible in the current zoom extent. The lowerValues and the colours in between will be rearranged to fit between the minimum and maximum. Thus the colours for given values change.
If no ordinal value is specified, then the colours are just rearranged. However, if e.g. ordinal value = 0 is specified and 0 values have a white colour, then the rescaling will take this into account so that 0 values always stay coloured white. This can be used for instance when displaying temperatures, where red colours are used for positive values and blue colours are used for negative values and zero values are coloured white.
This The rescaling will not happen automatically but will be applied when using the "rescale classification" right mouse option:
Here <rescaleAroundOrdinalValue>0</rescaleAroundOrdinalValue> is used, which means the classbreak with 0 remains unchanged, only the other classbreaks are rescaled:
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