Field mapping using a computer: assessment of some computing errors and further improvement in accuracy

The small errors still encountered when computing a field, particularly near the matching boundary, are examined more closely. Considerable reduction of these errors results when applying a better (2nd order) equation for interpolating the potential of a `virtual node¿ near the boundary. An accuracy better than 1 part per 1000 of the overall potential everywhere in the field of a test example is attained.