Magnetic field effects on the accuracy of ionospheric mirror models for geolocation
Abstract
The geolocation of an uncooperative HF emitter is based on observations of the azimuth and elevation (angle of arrival; AoA) of its signals as they arrive at a surveillance site, along with a model of the propagation medium. The simplest propagation model that provides an estimate of the location of the emitter is based on the use of a horizontal mirror placed at the appropriate altitude. If there are large‐scale horizontal ionospheric gradients or traveling ionospheric disturbances present, tilts derived from a suitable ionosonde or from the AoA of convenient known emitters (check targets) may be applied to the mirror before geolocation is performed. However, the methodology of this approach to geolocation completely ignores the Earth's magnetic field, producing errors that can reach 25% of range for a short range (less than 100 km) low‐latitude target. The errors are generally smaller at midlatitudes. This paper investigates and characterizes these errors in terms of wave polarization, magnetic dip, circuit length, and azimuth relative to the direction of the magnetic field. The magnetic field also affects the procedure of using tilts derived from check‐target AoA because the field effects can masquerade as tilts of unknown magnitude.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2016
- Source ID
- 10.1002/2015rs005884
Entities
People
- E. V. Dao
- Jonah J. Colman
- Leo F. Mcnamara
Organizations
- Air Force Research Laboratory