Evaluation of JSAF EM propagation prediction methods for navy continuous training environment / fleet synthetic training results and recommendations: part I – evaluation of current JSAF EM propagation modeling
Guest, Peter S.
Frederickson, Paul A.
Guest, Arlene A.
MetadataShow full item record
The EM propagation model currently used in JSAF is “FFACTR” which is a part of the Engineers Refractive Index Prediction System (EREPS) Tactical Decision Aid (TDA) developed by what is now SPAWARS SSC San Diego in 1988. This model is no longer supported by SPAWARS or any other group and has been replaced; it is obsolete. This model is able to represent some realistic features including: (1) decrease in signal strength (increase in propagation loss) with range, (2) more interference lobes for higher elevation and higher frequency transmitters, and (3) increased surface ranges for evaporation and surface ducts, and also with greater K-Factors. However the following deficiencies were noted: 1. Duct Strength (M value change) had no effect on the JSAF predictions. 2. The JSAF interference lobes caused by interaction between direct and surface-reflected radiation did not have the correct spacing..3. The effects of surface ducts were not realistically modeled. In reality, ducts create complex signal strength patterns and at the surface typically show “skip and hop” bands of increased and decreased signal strength. The JSAF predictions were unrealistically smooth and showed no skip patterns. 4. The far range (> 30 km) JSAF predictions appeared to have too strong signals and very simplified “flat” patterns. It appears that the JSAF EM model was not designed for these regions. 5. The standalone version used in this had no consideration for geographic location for predicting duct effects. Other versions do allow duct features to vary strongly over the Earth’s surface. 6. The varying “leakage’ of radiation above ducts was not captured by the JSAF predictions. 7. The radar “hole” that is usually present just above duct tops was not seen in the JSAF predictions. It is clear that there are considerable and significant weaknesses in the JSAF EM propagation prediction model which result in unrealistic range predictions, particularly in situations when ducting is present.
NPS Report NumberNPS-MR-12-001
Showing items related by title, author, creator and subject.
Twigg, Katherine L. (Monterey, California. Naval Postgraduate School, 2007-09);Surface electromagnetic propagation over the ocean is highly sensitive to near-surface atmospheric variability, particularly the height of the evaporation duct. Seasonal variation in near-surface meterological factors and ...
Larkin, John W. (Monterey, California. Naval Postgraduate School, 1992-03);As microcircuit technology advances, there is an increased need for the dissipation of the heat which is generated. Extended surfaces are a useful toll in fulfilling the heat sink requirements for a microcircuit element. ...
Nelson, Douglas H.; Walters, Donald L.; MacKerrow, Edward P.; Schmitt, Mark J.; Quick, Charles R.; Porch, William M.; Petrin, Roger R. (2000-04);Laser speckle can influence lidar measurements from a diffuse hard target. Atmospheric optical turbulence will also affect the lidar return signal. We present a numerical simulation that models the propagation of a lidar ...