Positioning Techniques with Two GNSS Satellites over Time

Being able to obtain the location of the GNSS receiver at any instance is often a privilege. In some applications, location information at all instances might not be so important as long as the receiver is able to make sure that it can tell where it is at a specific time. Applications such as ensuring children are at home/school or tracking shipping containers might fall into this category. Both of the mentioned applications share some things in common such as both appear in locations with poor satellite visibility such as indoors or ports where many containers are often stacked together. Another common thing is that the users or items to be tracked often stay in the same location for hours. In this paper we propose the use of a TDOA-generated local tangent line from two GNSS satellites to estimate the location of the receiver over time. The algorithm involves solving the intersection of several locally generated straight lines. This method helps to keep the calculations simple and thus saves processing power and hence the battery life of the equipments. The system was tested by masking out satellites as if buildings or objects along both sides are blocking large segments of sky. Under extreme conditions, our experiments. results indicate that we are able to achieve reasonable accuracy of within 10 meters over a period of time. Some factors affecting the performance of the system are also discussed in this paper.