Land-based local ranging signal methods and systems

• Main Authors: ZIMMERMAN KURT R, COBB H. STEWART
• Format: Patent
• Language: English
• Published: 18.03.2008
• Subjects: ANALOGOUS ARRANGEMENTS USING OTHER WAVES; ANTENNAS, i.e. RADIO AERIALS; BASIC ELECTRIC ELEMENTS; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; ELECTRICITY; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION ORRERADIATION OF RADIO WAVES; MEASURING; PHYSICS; RADIO DIRECTION-FINDING; RADIO NAVIGATION; TESTING

To provide sub-meter accuracy in a local positioning system, ranging signals with a high modulation rate of code, such as 30 MHz, or more are transmitted. Code phase measurements may be used to obtain the accuracy without requiring relative motion or real time kinematic processing. The ISM or X-band is used for the carrier of the code to provide sufficient bandwidth within available spectrums. The length of codes used is less than or about a longest length across the region of operation, such as less than 15 kilometers in an open pit mine. The spread spectrum codes from different land-based transmitters are transmitted in time slots pursuant to a time division multiple access scheme for an increase in dynamic range. To avoid overlapping of code from different transmitters, each time slot includes or is separated by a blanking period. The blanking period is selected to allow the transmitted signal to traverse a region of operation. Differential measurements of signals received at a base station and a mobile receiver may improve accuracy.