Conventional satellite-based navigation systems do not provide required navigation performance and accuracy in indoor environments. This entails the development of indoor navigation systems that can either work independently or in conjunction with the satellite-based as well as on-board navigation systems. This paper discusses some of the existing indoor navigation systems before presenting a novel Acoustic Navigation and Guidance System (ANGuS). Echolocation exhibited by mammals like bats and dolphins as well as some visually impaired humans is discussed. Significant research efforts have focused on the dilution of precision for outdoor radio navigation systems, both terrestrial and satellite-based. However, indoor navigation systems pose considerably different challenges, which would potentially require a different approach from the techniques developed for outdoor navigation systems. One such approach would be how the issue of poor geometry is tackled for multistatic indoor navigation systems. Due to higher elevation angles, even a slight change in beacon arrangement indoors can significantly affect the geometry and consequently the position dilution of precision as well as the positioning error. An alternate positioning error estimation technique is proposed for high PDOP multistatic navigation systems, thus improving error budgeting and system design of indoor navigation systems. Experimental results of ANGuS, including static positioning tests, flight tests on an unmanned aerial platform, and ground tests on a tracked vehicle are discussed. A simulation case study looking at integration of on-board inertial measurement unit (IMU) with ANGuS is also discussed.