The Size and Shape of Typical Sweet Potatoes

Atotal of 457 U. S. grade number 1 sweet potatoes of four common commercial varieties, 199 from the 1983 crop and 258 from 1984, were measured using a digital image analysis system. Each potato was suspended in front of a light source and image edge data was taken about its longitudinal axis for 18 views, 10 deg of rotation apart. These data, plus measured weight and volume, were recorded on diskettes. The acquired data were used in an algorithm to calculate volumes and surface areas of the sweet potatoes. The mean difference for the calculated minus the measured volume was 1.92%. The range of differences was from 10.58% to +8.77%. Several possible sources of measurement error are discussed. Other programs were written to determine normalized averaged shapes for comparison of varieties and growing areas, to compare sweet potato shapes with prolate spheroids, and to determine functional relationships with which to predict surface area from easily obtained measurements.