Terrestrial Mapping
Many of the research and monitoring programs require survey data to produce topographic maps, cross sections, or surface area maps for analysis or change detection monitoring. The GCMRC Survey Department provides terrestrial mapping support to GCMRC researchers, contractors, and cooperators. Scientific research and monitoring projects requiring terrestrial mapping products include sediment storage and sand bar evolution studies, erosion monitoring, campsite monitoring, hydrologic modeling, and habitat monitoring in support of the Physical, Biological, and Cultural Programs. Each research project requires unique surveying procedures and protocols based on the required mapping products. These procedures and their execution are developed by the Survey Department in accordance with logistic and project requirements and subsequently, defined in a peer reviewed workplan.
Topographic maps are used for the GCMRC long-term monitoring of fine-grained sediment storage and transport for evaluating changes in volume and surface area of sediment, and for analyzing sand bar geomorphology. Cross sections of the Glen Canyon corridor are used to facilitate 2 and 3 dimensional hydrologic modeling. The NAU campsite and vegetation project monitors surface area of beaches along the river for the Park Service to determine campsite capacity. The endangered Kanab ambersnail (KAS) Habitat studies correlate the KAS population to the surface area of vegetated habitat.
Producing terrestrial topographic maps, cross sections, and area maps utilizes conventional total station technology to measure angles and distances. The total station is set up over a known control point and measures angles and distances (spherical coordinates) to another known control point (back site) to establish a horizontal and vertical reference.
In the Grand Canyon, the AZ State Plane Coordinate System is the reference system used for all the spatial data collected to produce mapping products. The total station measures distances with an infrared laser to a reflective prism and calculates the distance based on time. The associated vertical and horizontal angles turned to the reflective prism are measured internally by the total station. Post-processing of the angle and distances yield XYZ coordinate values (Cartesian coordinates). The total station operator sights on the prism atop a survey rod held by the Rodman. The Rodman systematically selects features to be surveyed and topographic point density that is appropriate to achieve the established requirements of the survey project. The raw survey data is logged electronically to a hand held data collector to improve productivity and remove the possibility of a hand-written number transposition error.
The electronic data collector is downloaded, and then the raw survey data is checked for errors and processed into spatial data or coordinates. Mapping products can then be generated by various survey and GIS software packages.