Bridges are an important part of the infrastructure of both road and rail networks. As bridge stocks age it is becoming increasing important to monitor their health and predict their lifespan. Current health assessment methods of visual inspection have many drawbacks and so non-destructive evaluation methods such as GPS are becoming more important. This study focuses on the use of single frequency GPS for bridge deformation monitoring. Previous studies have focussed on the use of more expensive dual frequency receivers. This thesis has resulted in the development of single frequency processing software that has enabled these receivers to be used in bridge deformation situations. Improvements in integer ambiguity resolution methods mean it is now possible to be resolve ambiguities instantly for small bridges and greatly reduces ambiguity time for long bridges. The development of this software is outlined along with results from bridge trials. The thesis further looks at extensions to the use of single frequency GPS by outlining experiments conducted with Garmin handheld receivers and also with INS 1 00 receivers measuring at 50 Hz. The potential to use Garmin receivers in monitoring applications is demonstrated. The use of 50 Hz data enables the identification of higher frequency bridge dynamics than has ever been possible before. The final investigation looks at using pseudolites to augment the current GPS constellation specifically for bridge monitoring applications. The introduction of pseudolites led to improvements in all three coordinate directions, with the most improvement being seen in the vertical direction.