Altitude aiding for GPS systems using elevation map datasets

This paper reports the development of a DGPS navigation system integrated with altitude aiding. In this system, a digital height dataset is used for altitude augmentation. A two-dimensional (2-D) positioning algorithm is discussed and modified based on previous publications. The developed algorithm was implemented on the Brunel Inverse DGPS system. The performance of the new developed system is experimentally verified and compared with three-dimensional (3-D) GPS and DGPS systems. The experimental results showed 86 % availability of positioning services; whereas for the 3-D GPS system alone, the availability was only 63 % of time. In addition, the accuracy of the system was improved from 7(.)1 to 6(.)1 in (RMS) for GPS and from 6(.)0 to 5(.)1 in (RMS) for DGPS when compared to standalone 3-D modes.