Compass Measurement – Still a Suitable Surveying Method in Specific Conditions

Abstract

The compass measurement is one of the customary surveying methods that is used almost from the beginning of systematic geodesy and cartography. After the periods of the decreased use of this method, it was partially renewed by the ascension of the Field-Map technology that connects the compass measurement with the software tools for the environment mapping. It is currently mostly used for the forestry under-canopy mapping and other special tasks, where the current progressive technologies, especially photogrammetry and GNSS, can be used only with complication. The Field-Map set can include either the laser rangefinder Impulse LR 200 with MapStar Compass Module II compass, or TruPulse laser rangefinder that allows also the azimuth measurement. The research was aimed on the accuracy of mentioned devices. The measured lengths and azimuth were evaluated primarily. The evaluation of the field condition results showed the mean length error 0.07-0.09 m for Impulse rangefinder, while 0.25-0.29 m for TruPulse rangefinder. The mean azimuth error was around 0.5 degree for MapStar compass and above 3 degrees for TruPulse. After this basic evaluation the data were used for the computation of four compass traverses using various measurement and computation methods. The results showed, that the compass measurement, especially using the Impulse + MapStar set, can be still a suitable method for lower accuracy surveying, although effective only in specific conditions.

Direct Measurement of Tree Height Provides Different Results on the Assessment of LiDAR Accuracy

“…Field-based surveying methods can influence the accuracy of tree height estimation and usually are affected by lack of precision [42,43]. The model of handheld laser rangefinder (e.g., Impulse or Truepulse) affects the quality of compass measurements [44,45]. In our study, we used a Truepulse 360B device that is affected by a length measurement error of 30 cm and azimuth error of 3 degrees [45].…”

“…The model of handheld laser rangefinder (e.g., Impulse or Truepulse) affects the quality of compass measurements [44,45]. In our study, we used a Truepulse 360B device that is affected by a length measurement error of 30 cm and azimuth error of 3 degrees [45]. When using Suunto hypsometers the standard error in tree height estimation has proven to be between 0.4 and 0.8 m [46,47].…”

Static Positioning under Tree Canopy Using Low-Cost GNSS Receivers and Adapted RTKLIB Software

“…for the creation of forestry maps in Slovakia. However, from a practical point of view, the 20 min observation period per point is quite long considering other methods with similar accuracy, for example traditional compass measurement [ 61 ] or current mapping using aerial photogrammetry/lidar [ 62 , 63 ]. For ten single- and multi-frequency smartphones, Purfürst [ 3 ] reported circular errors probable (CEP 50 , i.e., medians) between 3.28 m and 8.05 m after multiple sessions of 10 min observations under various forest conditions.…”