Log-Linear Transform

The Log-Linear Transform dialog enables you to specify the minimum, maximum and log contour interval. It is most appropriate for data distributions covering many orders of magnitude, with clustered data in distinct ranges.

Zone Colour Ranges using Log-Linear Transform

All values of the input grid that are < 1 are ignored. The colour distribution is calculated on the range 1 or min of the data distribution (whichever is less) and max value of the grid. The log of the two end values is taken, then the bin boundaries are calculated using the linear transform method over these log ranges. The reported bin boundary values, however, are 10 to the power of the calculated logarithmic interval values.

Furthermore, if a contour interval is provided, the bin boundaries are calculated as multiples of the log10 of this contour interval.

For example lets say the data distribution range is -3000, +5000, and the contour interval is entered as 4.

The bin boundaries will be calculated over the range 1, 5000.

The log interval is Log₁₀(4) = 0.60206, and the bins will be multiples of 0.60206:

Interval
0.60206
1.20412
1.80618
2.40834
3.01030
3.61236

Bin boundary value
4
16
64
256
1024
4096