Soil apparent electrical conductivity (ECa) is a vital metric in Precision
Agriculture and Smart Farming, as it is used for optimal water content
management, geological mapping, and yield prediction. Several existing methods
seeking to estimate soil electrical conductivity are available, including
physical soil sampling, ground sensor installation and monitoring, and the use
of sensors that can obtain proximal ECa estimates. However, such methods can be
either very laborious and/or too costly for practical use over larger field
canopies. Robot-assisted ECa measurements, in contrast, may offer a scalable
and cost-effective solution. In this work, we present one such solution that
involves a ground mobile robot equipped with a customized and adjustable
platform to hold an Electromagnetic Induction (EMI) sensor to perform
semi-autonomous and on-demand ECa measurements under various field conditions.
The platform is designed to be easily re-configurable in terms of sensor
placement; results from testing for traversability and robot-to-sensor
interference across multiple case studies help establish appropriate tradeoffs
for sensor placement. Further, a developed simulation software package enables
rapid and accessible estimation of terrain traversability in relation to
desired EMI sensor placement. Extensive experimental evaluation across
different fields demonstrates that the obtained robot-assisted ECa measurements
are of high linearity compared with the ground truth (data collected manually
by a handheld EMI sensor) by scoring more than 90% in Pearson correlation
coefficient in both plot measurements and estimated ECa maps generated by
kriging interpolation. The proposed robotic solution supports autonomous
behavior development in the field since it utilizes the ROS navigation stack
along with the RTK GNSS positioning data and features various ranging sensors.Comment: 15 pages, 16 figure