To put a real-world spin on this topic, consider that the above maps represent the plume of a 1DNAPL contaminant, such as 2PCE. Displaying the contours using a logarithmic scale provides a much better indication of the distribution of the concentration throughout the map. Displaying a contour map of this data using a linear scale generates lines of equal concentration that lose much of the variability in the data. You can see from the color scale in example C that the concentration (ppm) values range over 5 orders of magnitude, from 0.001 to 4000. ( C:\Program Files\Golden Software\Surfer 12\Samples\Logarithmic.srf ) Gridding data as logarithmic, displaying with logarithmic levels and colormap. Gridding data as logarithmic, displaying with linear levels and colormap.Ĭ. Gridding data as linear, displaying with a linear levels and colormap.ī. The example shows how the same dataset is displayed when:Ī. If the contours are displayed with a linear colormap, a logarithmic color scale bar would have a meaningless correlation to the map.īelow I have included a simple illustration from the Logarithmic sample file that comes with Surfer 12. It is important that the colormap and the contour map display using the same scaling. Why should I set the colormap for that same contour map to Logarithmically-scaled? When you choose the Log, save as log option, log-distributed data is displayed much more accurately than the linear contour map, as it more closely honors the very low and very high data points.
Why should I set the Level method for a contour map using my log save as log file to Logarithmic? However, the areas with the very low data values and the areas with the very high data values are smoothed over. This option is a good choice if your data spans several orders of magnitude and you want the resulting Z value in the grid file to be in the same units as your original data. Why would I grid my data as log save as linear over log save as log? This feature can be used to display your data in a way that accurately conveys the logarithmic information in an easy to interpret display.įirst, it would be useful to ask a few simple questions about why you would want to use this feature. A great new feature has been added in Surfer 12! There is now the ability to grid or display logarithmic data.
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