Advanced mission planning tool for real-time kinematic (RTK) GPS surveying
Conventional mission planning in GPS surveying involves locating a site with minimal obstructions and determining satellite availability at the location to be surveyed. Tools used in the planning process usually include topographic maps and satellite availability software. In recent years, with the advent of Real Time Kinematic (RTK) GPS surveying, it is possible to obtain centimeter-level accuracy while in the field. Applications for RTK GPS surveying include, but are not limited to: construction layout, land survey, photogrammetric survey control, and GIS updating. One of the key factors in the RTK GPS technique is the data link between the reference station and rover. Without this link RTK GPS results are not attainable in the field. For this reason mission planning in RTK GPS surveying takes on another level of complexity: not only does the reference station have to visible to the satellites, but it must also be visible to the rover. However, available mission planning tools do not provide a means to predict the data link coverage of the reference station. The purpose of this investigation is to determine the best wave propagation model or models to be used in an RTK GPS survey mission planning tool. This study will present current wave propagation models being used by communications planning software and then use these models to predict data link coverage. The performance of these models was evaluated through field testing of two RTK GPS systems. This investigation concludes that there are three wave propagation models that could be used to accurately predict data link coverage by using only digital terrain information. The implementation of these models relies on available documentation and potential source code. In researching this project, it was evident the availability of documentation varies between models. Based on performance criteria and implementation considerations, two models are recommended to be implemented into a mission planning tool for RTK GPS surveying: Parabolic Equation and TIREM.