Method for substituting at least one high quality position measurement taken before an interrupting event with a set of upgraded low quality position measurements provided by the same source of measurements after the interrupting event

• US 7,747,384 B1
• Filed: 05/17/2005
• Issued: 06/29/2010
• Est. Priority Date: 06/06/2002
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Smith, Scott R., Nadkarni, Vivek Bhalchandra
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): LOUIE, WAE LENNY
• Application Number:
  US11/133,798
• Time in Patent Office: 1,869 Days
• Field of Search: 701/200, 701207-216, 701/224, 701/226, 342/352, 342/358, 34235701-35715
• US Class Current: 701/207
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled

Abstract

A method for substituting at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of the object provided by the same source of measurements after the interrupting event. The method comprises the following steps: (A) obtaining at least one high quality position measurement of the object provided by a source of measurements before the interrupting event; (B) saving at least one high quality position measurement of the object; (C) if at least one position measurement of the object provided by source of measurements after the interrupting event is of substantially high quality, using at least one position measurement of substantially high quality of the object for navigation purposes of the object; and (D) if each position measurement of the object provided by the source of measurements after the interrupting event is of low quality, and if there is not at least one restoration event; then upgrading at least one position measurement of the object by using an upgrade algorithm.

Claims

1. A method for substituting at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of said object provided by the same source of measurements after said interrupting event;

said method comprising the steps of;

(A) obtaining at least one high quality position measurement of said object provided by a source of measurements before said interrupting event;

said source of measurements before said interrupting event is selected from the group consisting of;

{a carrier differential Satellite Positioning System SATPS;

a code differential SATPS;

an autonomous SATPS;

an Inertial Navigation System (INS); and

a Pseudolite-Based Positioning System};

(B) saving said at least one high quality position measurement of said object by using a memory block;

(C) if said at least one position measurement of said object provided by said source of measurements after said interrupting event is of substantially high quality;

or if each said position measurement of said object provided by said source of measurements after said interrupting event is of low quality, and if there is a restoration event, and if at least one said position measurement of said object provided by said source of measurements after said restoration event is of substantially high quality;

then using said at least one position measurement of substantially high quality of said object for navigation purposes of said object obtained in said step (A);

and

(D) if each said position measurement of said object provided by said source of measurements after said interrupting event is of low quality, and if there is not at least one restoration event;

or, if each said position measurement of said object provided by said source of measurements after said interrupting event is of low quality, and if there is a restoration event, and if each said position measurement of said object provided by said source of measurements after said restoration event is of low quality;

then upgrading said at least one position measurement of said object by using an upgrade algorithm;

said upgrade algorithm comprising at least the following steps;

(D1) if a set of Correction Terms is substantially unavailable, computing said set of Correction Terms;

wherein said set of Correction Terms comprises a set of error estimates of said at least one low quality position measurement;

(D2) if said set of Correction Terms is substantially available, computing at least one system quality metric;

wherein each said system quality metric indicates whether or not said set of Correction Terms is substantially adequate for upgrading purposes;

(D3) if each said system quality metric indicates that said set of Correction Terms is substantially adequate for upgrading purposes;

setting a flag indicating said set of Correction Terms is substantially adequate for upgrading purposes, using said set of Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object and outputting said at least one upgraded position measurement of said object;

(D4) if at least one said system quality metric indicates that said set of Correction Terms is substantially inadequate for upgrading purposes, setting a flag indicating said set of Correction Terms is substantially inadequate for upgrading purposes, and checking whether said set of Correction Terms can be updated to become substantially adequate for upgrading purposes;

(D5) if said set of Correction Terms is updatable to become substantially adequate for upgrading purposes;

updating said set of Correction Terms, using said set of updated Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object, and outputting said at least one upgraded position measurement of said object;

and

(D6) repeating said steps ((D1)-(D5)) for each next epoch of position measurement of said object;

wherein each said low quality position measurement of said object includes an epoch timing coordinate indicative of when said low quality position measurement of said object was taken;

and wherein said at least one position measurement of said object is of low quality if said low quality position measurement of said object includes an unacceptable error in said position measurement of said object, or is not substantially recent.

2. The method of claim 1, wherein said step (C) further comprises the step of:

(C1) detecting said interrupting event by using a CPU configured to compute a satellite tracking list;

a First Memory Block configured to store a satellite tracking list computed at a prior epoch; and

a Second Memory Block configured to store a satellite tracking list computed at a current epoch;

wherein said CPU is configured to compare the contents of said First Memory Block and said Second Memory Block; and

wherein if these contents are not identical, then said satellite tracking list has changed from said previous epoch and said change in said satellite tracking list constitutes said interrupting event;

wherein said interrupting event is selected from the group consisting of;

{an event leading to an unacceptable error in said position measurement of said object; and

an event causing said at least one high quality position measurement of said object to be not substantially recent}.

3. The method of claim 1, wherein said step (C) further comprises the step of:

(C2) detecting said restoration event by using a CPU configured to compute a satellite tracking list;

a First Memory Block configured to store a satellite tracking list computed before an interrupting event; and

a Second Memory Block configured to store a satellite tracking list computed at a current epoch;

wherein said CPU is configured to compare the contents of said First Memory Block and said Second Memory Block; and

wherein if these contents are identical, then said satellite tracking list has changed to match said satellite tracking list computed before said interrupting event, and wherein such match constitutes said restoration event;

wherein said restoration event is selected from the group consisting of;

{an event leading to an acceptable error in said position measurement of said object; and

an event causing said at least one high quality position measurement of said object to be substantially recent}.

4. A computer-readable storage medium useful in association with a radio navigation chip, said chip having a processor and memory, said chip is configured to substitute at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of said object provided by the same source of measurements after said interrupting event;

said computer-readable storage medium including computer-readable code instructions configured to cause said processor to execute the steps of an upgrade algorithm comprising at least the following steps;

(A1) if a set of Correction Terms is substantially unavailable, computing said set of Correction Terms;

wherein said set of Correction Terms comprises a set of error estimates of said at least one low quality position measurement;

(A2) if said set of Correction Terms is substantially available, computing at least one system quality metric;

wherein each said system quality metric indicates whether or not said set of Correction Terms is substantially adequate for upgrading purposes;

(A3) if each said system quality metric indicates that said set of Correction Terms is substantially adequate for upgrading purposes;

setting a flag indicating said set of Correction Terms is substantially adequate for upgrading purposes, using said set of Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object and outputting said at least one upgraded position measurement of said object;

(A4) if at least one said system quality metric indicates that said set of Correction Terms is substantially inadequate for upgrading purposes, setting a flag indicating said set of Correction Terms is substantially inadequate for upgrading purposes, and checking whether said set of Correction Terms can be updated to become substantially adequate for upgrading purposes;

(A5) if said set of Correction Terms is updatable to become substantially adequate for upgrading purposes;

updating said set of Correction Terms, using said set of updated Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object, and outputting said at least one upgraded position measurement of said object;

and

(A6) repeating said steps ((A1)-(A5)) for each next epoch of position measurement of said object.

5. A computer program product that includes a computer readable medium having a sequence of instructions which, when executed by a processor, causes the processor to execute a process for substitution at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of said object provided by the same source of measurements after said interrupting event;

the process comprising an upgrade algorithm comprising at least the following steps;

(A1) if a set of Correction Terms is substantially unavailable, computing said set of Correction Terms;

wherein said set of Correction Terms comprises a set of error estimates of said at least one low quality position measurement;

(A2) if said set of Correction Terms is substantially available, computing at least one system quality metric;

wherein each said system quality metric indicates whether or not said set of Correction Terms is substantially adequate for upgrading purposes;

(A3) if each said system quality metric indicates that said set of Correction Terms is substantially adequate for upgrading purposes;

setting a flag indicating said set of Correction Terms is substantially adequate for upgrading purposes, using said set of Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object and outputting said at least one upgraded position measurement of said object;

(A4) if at least one said system quality metric indicates that said set of Correction Terms is substantially inadequate for upgrading purposes, setting a flag indicating said set of Correction Terms is substantially inadequate for upgrading purposes, and checking whether said set of Correction Terms can be updated to become substantially adequate for upgrading purposes;

(A5) if said set of Correction Terms is updatable to become substantially adequate for upgrading purposes;

updating said set of Correction Terms, using said set of updated Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object, and outputting said at least one upgraded position measurement of said object;

and

(A6) repeating said steps ((A1)-(A5)) for each next epoch of position measurement of said object.

6. An apparatus for substituting at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of said object provided by the same source of measurements after said interrupting event;

said apparatus comprising;

(A) a source of position measurement selected from the group consisting of;

{a carrier differential Satellite Positioning System SATPS;

a code differential SATPS;

an autonomous SATPS;

an Inertial Navigation System (INS); and

a Pseudolite-Based Positioning System};

(B) a memory block configured to save said at least one high quality position measurement of said object;

(C) a means for detecting an interrupting event comprising;

a CPU configured to compute a satellite tracking list;

a First Memory Block configured to store a satellite tracking list computed at a prior epoch;

a Second Memory Block configured to store a satellite tracking list computed at a current epoch;

wherein said CPU is configured to compare the contents of said First Memory Block and said Second Memory Block;

and wherein if said contents are not identical, then said satellite tracking list has changed from said previous epoch and said change in said satellite tracking list constitutes said interrupting event;

wherein said interrupting event is selected from the group consisting of;

{an event leading to an unacceptable error in said position measurement of said object; and

an event causing said at least one high quality position measurement of said object to be not substantially recent};

(D) a means for detecting a restoration event comprising;

a CPU configured to compute a satellite tracking list;

a First Memory Block configured to store a satellite tracking list computed before an interrupting event;

a Second Memory Block configured to store a satellite tracking list computed at a current epoch;

wherein said CPU is configured to compare the contents of said First Memory Block and said Second Memory Block;

and wherein if said contents are identical, then said satellite tracking list has changed to match said satellite tracking list computed before said interrupting event; and

wherein such match constitutes said restoration event; and

wherein said restoration event is selected from the group consisting of;

{an event leading to an acceptable error in said position measurement of said object; and

an event causing said at least one high quality position measurement of said object to be substantially recent};

and

(E) a means for upgrading said at least one position measurement of said object further comprising;

an upgrade algorithm.

7. The apparatus of claim 6, wherein said upgrade algorithm of means (E) further comprises at least the following steps:

(E1) if a set of Correction Terms is substantially unavailable, computing said set of Correction Terms;

wherein said set of Correction Terms comprises a set of error estimates of said at least one low quality position measurement;

(E2) if said set of Correction Terms is substantially available, computing at least one system quality metric;

wherein each said system quality metric indicates whether or not said set of Correction Terms is substantially adequate for upgrading purposes;

(E3) if each said system quality metric indicates that said set of Correction Terms is substantially adequate for upgrading purposes;

setting a flag indicating said set of Correction Terms is substantially adequate for upgrading purposes, using said set of Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object and outputting said at least one upgraded position measurement of said object;

(E4) if at least one said system quality metric indicates that said set of Correction Terms is substantially inadequate for upgrading purposes, setting a flag indicating said set of Correction Terms is substantially inadequate for upgrading purposes, and checking whether said set of Correction Terms can be updated to become substantially adequate for upgrading purposes;

(E5) if said set of Correction Terms is updatable to become substantially adequate for upgrading purposes;

updating said set of Correction Terms, using said set of updated Correction Terms to upgrade said at least one low quality position measurement of said object to obtain said at least one upgraded position measurement of said object, and outputting said at least one upgraded position measurement of said object; and

(E6) repeating said steps ((E1)-(E5)) for each next epoch of position measurement of said object.