Visualization of spatio-temporal GPS uncertainty within a GIS environment

The importance of accurate registration of GPS (Global Positioning System) tracked objects embedded within a GIS (Geographic Information Systems) context has emerged as a critical need in several land, marine, and air navigational systems both for civilian and defense applications. The objective of this work is to measure, model and geo-spatially- register the positional accuracy of objects carrying GPS receivers against a GIS background. Although positional accuracy is affected by a number of factors, in this work we have focused on GPS modes (standalone or differential), type of environment (urban or foliage), and type of expected movement of objects. The Ashtech Z-12 sensor is used to collect the data. Linear models are used to estimate the errors associated with the horizontal position information. This error is then visualized upon a 1/2 foot resolution aerial imagery of the UCSC (University of California, Santa Cruz) campus. Estimates of speed and direction errors are used to create visualizations of spatio-temporal uncertainty associated with an object walking through the campus.