Site-specific decision-making based on RTK GPS survey and six alternative elevation data sources: watershed topography and delineation

摘要

Soil erosion modeling and assessment requires substantial and accurate topographic data to obtain meaningful results for decision-making regarding soil and water conservation practices. Today '5 precision farming equipment includes Global Positioning System (GPS) technology to determine the location of spatially distributed data. Besides the main purpose of tagging site-specific information to a unique location (x and y), the elevation data (z) recorded has the potential to be used for topographic analysis, including delineation of flowpaths, channels, and watershed boundaries. In addition to GPS-based data collection at various accuracy levels, surveying companies and the U.S. Geological Survey also provide alternative sources of topographic information. Spatial statistical tests were performed to determine if some of these data sources - in particular the ones free of charge or gathered with inexpensive equipment - are sufficiently accurate to represent field or watershed topography and meaningfully apply detailed, process-based soil erosion assessment tools. The most expensive alternatives were most useful for determining elevation and slopes in the flow direction, while there was not much difference between alternatives in obtaining upslope drainage areas and delineation of the channel network and watershed boundary. This is the first of two articles analyzing the impact of the accuracy of six alternative topographic data sources on watershed topography and delineation in comparison to GPS measurements using a survey-grade cm-accuracy GPS.