Assessing the accuracy of NRTK altimetric positioning for precision agriculture: test results in an olive grove environment in Southeast Spain.

Soil erosion modeling in olive groves requires precise and accurate spatial data for the representation of topography associated with each time epoch considered. The precision and accuracy of altimetric values affect the quality of the digital elevation model (DEM) and therefore these requirements must be added to the necessity to generate high resolution DEMs. The increase of quality implies: 1. Improving the quality of the instrumentation and methodology applied in the field data collection and 2. Minimizing errors from the interpolation algorithm used to generate the digital terrain model. Currently, RTK networks are an indispensable complement to global navigation satellite systems (GNSS) precise positioning. The availability of highly accurate three-dimensional real time positioning has opened the door to new applications, making network-based real time kinematic (NRTK) positioning an attractive spatial data source for modeling soil erosion in small areas. This paper analyzes the quality of NRTK altimetric positioning supported by a local active network and its application in a test olive grove in SE Spain for soil erosion modeling. An evaluation procedure was implemented at several test sites distributed throughout an olive grove environment with special emphasis on filtering and checking the NRTK solutions in the vertical component. The precision in this component revealed a mean value of 15 mm and the vertical accuracy reached maximum values of 30 mm. In order to generate high resolution and accuracy DEM from the NRTK data, cross sections on the test olive grove were surveyed. The average altimetric quality value (CQ1D) of points surveyed was 0.017 m, according to the standard deviation estimated at test points. Based on the quality results, NRTK positioning is an accurate and reliable methodology for monitoring the erosion processes of small areas in an olive grove environment. [ABSTRACT FROM AUTHOR]