Abstract
Tone-density is one of the most important elements in airphoto interpretation on geology, soils and vegetation. It depends on such various factors as flight conditions, reflextion ratio of the surface controled by color, moisture content, etc., and processing conditions, so it has been apt to be treated relatively or qualitatively. The author tried to clarify the role of tone-density in interpreting soil properties quantitatively by using photo-densitometers both of convenient type and automatic type. Through the case study in peat bog regions he pointed out that the interpretation of soil conditions can be done with high accuracy by an analysis of tone-density alone, if the quality of photographs is adequate.
