To produce accurate and repeatable tomograms of trees with complex shapes, it is essential to measure the sensor positions precisely. Accuracy of the position of sensors affects estimated stress wave velocity, the shape of the tomogram, the size of the defect, and the estimated loss in load carrying capacity.

Provided that sensor positions are accurately recorded and documented, tomograms can reliably be repeated by different assessors over periods of years. Assessments based on complex calculations like loss of section modulus should be treated with caution, because they accumulate and amplify all sources of variation.

Precise sensor positions in tomography can be measured quickly.

Often, the stem surface of mature London plane trees is bumpy. Our results, derived from a thorough characterization of the stem surface, tomography, and thermography, show that this does not indicate inner defects.