A Web-based Automated Gps Processing System

In the conventional scenario for GPS surveying based on the post-processed mode, users have to purchase a minimum of two sets of GPS receiver hardware, as well as the associated processing software package. This is not only a significant capital cost, but the GPS survey operation incurs additional logistical costs due to the need to operate both a Base (or Reference) receiver as well as the User receiver. In addition, in many instances the data post-processing step may be more awkward and labour-intensive (and therefore more costly) than the field data capture task, involving as it does the downloading of two data files into a PC, the operation of complex software (especially for users with minimum experience with GPS technology), and the subsequent transformation of the coordinate results into a form appropriate for the application. Use of real-time techniques is one solution to this problem, but there are many constraints to such an implementation, such as cost, distance from the Reference receiver, and the need for special communications hardware. On the other hand, a web-based GPS processing system could help users in a number of ways. A web site can be established that would accept GPS data and automatically process it. In this way the cost of GPS surveying could be reduced, as users will no longer need to buy and maintain any data processing software, or even understand the operation of such software! This web server application would allow users to send their data (in the RINEX format so that its instrument specific data files need not be used) via the Internet. The web application can be hosted by a computer anywhere in the world! Examples of such services already exist. The users will then be notified of their results by e-mail after the data processing step has been completed. In addition to such an implementation where the user submits BOTH the Reference and User receiver data files, the system can be improved so that the web application is connected to one or more Reference receivers. In this implementation, the User need only operate one GPS receiver. The complementary Reference data file is obtained from a database. In this way, data processing schemes not possible with commercial off-the-shelf GPS baseline software can be used. For example, true GPS network-based processing (where multiple Reference receiver data is used) is possible, permitting higher performance (in the form of higher accuracy, less observation time, or longer baselines) than is currently the case with single baseline modes of positioning. This paper describes how GPS carrier phase data processing via Internet could be implemented. The design and configuration of a pilot system will be discussed and some results presented.