Magnetically stabilized forward observation platform

A method for determining a position of a target comprising providing a target position measurement system having a computer embedded therein performing the steps of:

• determining the location coordinates of an observation position;
• determining an attitude estimate of a system reference platform at said observation position, said attitude estimate including an azimuth estimate and a vertical attitude estimate;
• said determining said attitude estimate performed with reference to:
• a three-axis rate gyro triad sensing body motion of said reference platform,
• a three-axis accelerometer triad sensing the earth's gravity vector and sensing body motion of said reference platform,
• a GPS receiver providing position and velocity information of said reference platform, and
• a three-axis magnetic sensor mounted to said reference platform for sensing the earth's magnetic field, said determining said attitude estimate including the step of correcting said vertical attitude estimate based on said three-axis magnetic sensor;
• said target position measurement system further performing the steps of:
• determining a line of sight direction from said reference platform to said target, said line of sight direction including angle coordinates relative to said reference platform;
• determining a distance to said target along said line of sight direction;
• and
• extrapolating from said observation position along said line of sight direction by said distance to said target to determine said target position.

A system for determining a position of a target comprising

• (a) an inertial measurement unit, said inertial measurement unit comprising:
• a level sensor having at least two axes mounted to said reference platform;
• (b) a three axis magnetic sensor mounted to said reference platform for sensing the earth's magnetic field;
• (c) a position source for determining a coordinate position of the reference platform;
• (d) a target sighting device, said target sighting device aligned with said inertial measurement unit and said three axis magnetic sensor, said target sighting device for finding angle coordinates defining a line from said reference platform to the target;
• (e) a target distance determination device for determining target distance from said reference platform along said angle coordinates;
• and
• (f) a state estimation processor for combining data from the level sensor with data from the three axis magnetic sensor to generate platform attitude information;
• wherein said position of said target is computed based on said coordinate position of the reference platform summed with a position vector having a length according to said target distance determination device and said position vector having a vector direction in accordance with said angle coordinates defining said line from said platform to said target, said angle coordinates in accordance with said platform attitude information;
• and
• wherein the level sensor and three axis magnetic sensor provide redundant vertical information that cooperates to generate elevation axis information for said line from said reference platform to said target.