Range precision in forestry with Reflectorless Total Station

Key words: 
• forest mensuration /
• total station /
• measuring distance by reflectorless /
• range precision

Abstract: The Reflectorless Total Station, a convenient and efficient instrument for distance measurement used more in construction surveying than in forestry, was employed to determine the influence of different factors, such as trees, walls, distance, and angle of incidence, on precision distance measurements in forestry and to determine its feasibility for use with forest surveys, a Reflectorless Total Station （SOKKIA SET1X Total Station） with trees and walls as survey targets was tested. Experimental results on precision of distance measurements showed that （1） the material quality of a wall had little effect, its error is about 0.5 mm; whereas, （2） different tree species has varying degrees of bark roughness, it had the most influence to precision distance. For example, maximum error reached 2.769 mm with a measuring distance of 20 m. （3） Surface color of the target object revealed that the darker the color the greater the influence with 1 mm of error for a 20 m distance. （4） The stability of reflected signals had an error proportional to the distance with close to 5 mm measurement error for 100 m. （5） When the angle of incidence was over 20, at 20 m the error was close to 2 mm. （6） for target trees with rough bark, randomly selected target points should be obtained to improve the precision of the distance measurement.［Ch, 2 fig. 6 tab. 17 ref.］