Solving the Grid-to-Ground Problem when Using High Precision GNSS in Archaeological Mapping

Increasingly, high-precision GPS/GNSS (global positioning system/global satellite navigation system) based real-time-kinematic methods are being used in the mapping of archaeological sites. However, when utilizing high-precision satellite-based methods for archaeological location purposes, there is a significant but usually unanticipated problem that must first be addressed if accurate measurements are to be made. Simply put, unless proper correction methods are used, horizontal distances between two locations determined by the GNSS method will differ from the measurements that are made by traditional survey methods. This difference between the two measurements is often referred to as the grid-to-ground problem. This article provides a process to address this problem.

Assisted GNSS in Smart Phones

It is difficult to acquire GNSS (Global Satellite Navigation System) signals in challenging environments such as urban canyons and indoors without any assistance information. The time-to-first-fix process is extremely long for positioning in such environments, especially for the case when the user is moving. In order to speed up the time-to-first-fix process, the receiver needs assistance information from a server for quickly acquiring and tracking the GNSS signals. This chapter introduces the assisted GNSS solution. It covers the topics of acquisition assistance, sensitivity assistance, and implementation for smart phones. The objective of the chapter is to provide the readers with a general overview of the Assisted-GNSS (A-GNSS) solution from the aspects of how the A-GNSS solution speeds up the acquisition process and improves the tracking sensitivity, what kinds of assistance data are needed, and how the assistance data is delivered to the mobile users. The chapter includes sections for an introduction to the topic, acquisition assistance, sensitivity assistance, A-GNSS implementation for smart phones, future directions, and brief conclusions.