Secondary Constraint

In Estimate Rank, Variance Rank, Uncertainty Rank, and Percentile Rank, the exact sample locations are optimized in a mathematical sense. For example, in Estimate Rank, the unsampled point with the highest concentration level is chosen as the first priority sample location. This location may, however, be located extremely close to another data point (in most cases the highest sample data point). While this satisfies the mathematical rule, it may not satisfy the user. Typically, samples should serve at least two purposes: 1) meet one of the approaches described above and 2) provide a good spatial spread to the sampling scheme.

Therefore, SADA allows a secondary constraint, where the user specifies a minimum distance between any new sample data locations and any previously sampled data. This is utilized on the **Sampling** tab of the **Control Panel** by checking the box to the left of **Separate by at least** and specifying a distance in the box to the right. New sample locations are then chosen with respect to both constraints. In the figures for the four approaches listed above, a constraining minimum distance of 240 meters was used.