Using reference frames and the Global Positioning System (GPS) to produce control networks for spatial data

Abstract

The Global Positioning System has enabled researchers to gather spatial data on a scale that was, until recently, cost prohibitive. Projects that cover an area of a few hectares can be included in data sets that cover entire countries. The ease at which point locations can be measured over large distances has highlighted an existing problem with data capture. Data collected using one set of control points may or may not overlay data collected using another. This thesis details a procedure for setting base control points that cover very large areas. Data obtained from the International GPS Service for Geodynamics (IGS) is used in conjunction with the International Terrestrial Reference Frame (ITRF) to establish control points anywhere in the world. Researchers utilizing these control points for base station locations or as registration points, are able to produce data with an absolute accuracy of 0.3 meter between projects, countries and continents. The problem of overlaying data has been reduced to the point that it is insignificant. Issues of datum and projections, and the use of existing data sets are addressed. Of special interest are the short project times and resulting cost savings over conventional methods. Specific projects in Texas, Azerbaijan, and Mali are presented. The project in Texas is the same size as the project in Azerbaijan, but on different continents. The project in Mali is much larger and has been the most comprehensive, from setting initial control points to training local researchers in data collection.