In 1993, when the 24-satellite Global Positioning System (GPS) constellation became fully operational, few outside the military recognized its impact on situational awareness (SA). For all of history, command and control had been reactive. The precise positioning, navigation, and timing (PNT) information GPS provides changed everything because coincident situational awareness became a reality.
Today’s military relies upon this real-time data to execute missions with the precision and minimal collateral damage the world has come to expect. However, GPS is not always available. Satellites can be obscured by vegetation, buildings, and terrain, reducing the capability of a unit back to reactive command and control. It makes no different what obscures the satellite, the outcome is a loss of reliable PNT data.
More reliable PNT systems are under development using multiple techniques to supplement GPS. These include signal sources such as:
- Improved GPS
- Foreign GNSS
- Iridium Communication Satellites
- eLORAN
In fact, the May/June 2016 issue of Inside GNSS featured an article in their Working Papers titled GNSS Evolutions for Maritime. The article discussed enhancements to GPS deemed necessary due to increasing maritime collisions and groundings, so the need is real even outside the military scope.
How does a test engineer challenge a new system against signal loss due to obstructions without constantly testing in the field? As part of their array of simulation products, Cast Navigation sells both an Interference Generation System and a Terrain Obscuration Program (TOP) to work in conjunction with their simulators. The TOPS program tests GPS receiver performance when one or more satellites are hidden behind terrain.
GPS signal simulators have been around for quite some time, and CAST Navigation sells a wide selection of them. PNT signal simulation is the one thing CAST Navigation does, and they do it well.
Engineers developing enhanced PNT systems can use the Cast Navigation’s TOP to evaluate performance when GPS signal is compromised by terrain or buildings. All the work can be done from inside the laboratory instead of out in the field.
When using the optional Advanced Visualization Option, Cast Navigation TOP software creates a 3-D visual presentation of terrain such as mountains. Together with real-time satellite positions, the software returns a visibility status for all satellites in the area. It does all this while using only modest computer resources.
Making sure an enhanced PNT system still functions with restricted or completely missing GPS data is fundamental to solving the problem of staying above the C2 Divide in all situations. The military has no intention of returning to a reactive situational awareness model, so development of the next generation PNT solution will continue.
Whenever a new PNT system emerges, it must be tested for effectiveness under less than ideal signal reception conditions. Terrain Obscuration Program by CAST Navigation helps test new systems and reduces field work. Contact CAST today at 978.858.0130 or castnav.com for more information.
