Apparatus to measure the earth's local gravity and magnetic field in conjunction with global positioning attitude determining

An apparatus for determination of the magnetic declination at a location on the earth, comprising:

• (a) a non-magnetic platform for providing a stable base;
• (b) at least three spaced apart non-collinear Global Positioning Sensor (GPS) receivers on the non-magnetic platform, the at least three GPS receivers adapted to receive electromagnetic signals from a plurality of satellite positions for providing signals indicative of the position of the at least three GPS receivers;
• (c) a 3-component magnetometer on the non-magnetic platform for measuring three independent components of the earth's magnetic field and providing signals indicative thereof;
• and
• (d) a processor for processing signals from the at least three GPS receivers and the 3-component magnetometer to determine the magnetic declination.

A method for determination of the magnetic declination at a location on the earth, comprising:

• (a) placing at least two Global Positioning Sensor (GPS) receivers, a 3-component accelerometer and a 3-component magnetometer on a non-magnetic platform, said at least two GPS receivers spaced apart from each other;
• (b) receiving electromagnetic signals from a plurality of satellites at the at least two GPS receivers;
• (c) providing signals indicative of the position of the at least two GPS receivers to a processor;
• (d) measuring three independent components of the earth's magnetic field with the 3-component magnetometer and providing signals indicative thereof to the processor;
• (e) measuring three independent components of acceleration using the 3-component accelerometer and providing signals indicative thereof to the processor;
• and
• (e) using the processor to process the signals from the at least two GPS receivers, the 3-component accelerometer and the 3-component magnetometer to determine the magnetic declination.

A method for determination of the magnetic declination at a location on the earth, comprising:

• (a) placing at least three spaced apart Global Positioning Sensor (GPS) receivers and a 3-component magnetometer on a stable non-magnetic platform, said three GPS receivers not arranged co-linearly;
• (b) receiving electromagnetic signals from a plurality of satellites at the at least three GPS receivers and providing signals indicative of the position of the at least three GPS receivers to a processor;
• (c) using the 3-component magnetometer on the non-magnetic platform to measure three independent components of the earth's magnetic field and providing signals indicative thereof to the processor;
• and
• (d) using the processor to process signals from the at least three GPS receivers and the 3-component magnetometer to determine the magnetic declination.

A method for obtaining corrected survey data in a borehole, comprising:

• (a) conducting a magnetic survey in a borehole over a known time interval to give a set of magnetic survey data referenced to the local magnetic field;
• (b) placing at least two spaced apart Global Positioning Sensor (GPS) receivers, a 3-component accelerometer and a 3-component magnetometer on a non-magnetic platform proximate to the borehole;
• (c) receiving electromagnetic signals from a plurality of satellites at the at least two GPS receivers;
• (d) providing signals indicative of the position of the at least two GPS receivers to a processor;
• (e) measuring three independent components of the earth's magnetic field with the 3-component magnetometer and providing signals indicative thereof to the processor at at least one time within the known time interval;
• (f) measuring three independent components of acceleration using the 3-component accelerometer at the at least one time within the known time interval and providing signals indicative thereof to the processor;
• (g) using the processor to process the signals from the at least two GPS receivers, the 3-component accelerometer and the 3-component magnetometer to determine a local magnetic declination at the at least one time within the known time interval;
• and
• (h) correcting the set of magnetic survey data from (a) using the determined magnetic declinations in (g) to give a set of corrected survey data of the borehole.

A method for obtaining corrected survey data in a borehole, comprising:

• (a) conducting a magnetic survey in a borehole over a known time interval to give a set of magnetic survey data referenced to the local magnetic field;
• (b) placing at least three spaced apart Global Positioning Sensor (GPS) receivers and a 3-component magnetometer on a stable non-magnetic platform proximate to the borehole, said three GPS receivers not arranged co-linearly;
• (c) receiving electromagnetic signals from a plurality of satellites at the at least three GPS receivers;
• (d) providing signals indicative of the position of the at least three GPS receivers to a processor;
• (e) using the 3-component magnetometer on the non-magnetic platform to measure three independent components of the earth's magnetic field and providing signals indicative thereof to the processor at at least one time within the known time interval;
• (f) using the processor to process signals from the at least three GPS receivers and the 3-component magnetometer to determine a magnetic declination at the at least one time within the known time interval;
• and
• (g) correcting the set of magnetic survey data from (a) using the determined magnetic declinations in (f) to give a set of corrected survey data of the borehole.