Different ways of presenting the effect of clearance

The first graph shows the way the field falls with distance for two different clearances of the line above ground. As expected, close to the line, the lower clearance produces the higher field.

The second graph shows exactly the same data but presented as percentage of the maximum field for each case rather than as the actual field value. This makes it look as if one field is falling much more rapidly with distance than the other, but this is just a consequence of plotting as a percentage rather than as the actual value.

Fields presented as percentages of the maximum have sometimes been used to suggest the calculations are unreliable because the field falls too rapidly. One example is "figure 1" here. This comparison is not valid unless the clearances are the same in each case.

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