Synchronized measurement sampling in a navigation device

Abstract

In a hot start mode of a navigation device, the process of obtaining pseudo-range measurements can be synchronized with the processes of tracking navigation satellites and initializing a positioning unit to compute a position, velocity, and time (PVT) solution of the navigation device. This can influence a time instant at which the pseudo-range measurements are determined and a time to first fix, depending on whether the navigation device is in a strong or weak signal environment. A measurement unit can receive a first indication that a predetermined number of navigation satellites have been acquired and that navigation signals transmitted by the acquired navigation satellites have been locked. The measurement unit can receive a second indication that the positioning unit has been initialized to compute the PVT solution. In response to receiving both indications, the measurement unit can obtain the pseudo-range measurements. Accordingly, the positioning unit can compute the PVT solution.

1 . A method comprising:
 acquiring and locking, at a navigation device, navigation signals transmitted by a predetermined number of navigation satellites;   initializing a positioning unit of the navigation device to determine navigation parameters of the navigation device;   determining, using the positioning unit of the navigation device, the navigation parameters of the navigation device based, at least in part, on the acquired and locked navigation signals; and   determining a position of the navigation device based, at least in part, on the navigation parameters.   
     
     
         2 . The method of  claim 1 , wherein in response to said acquiring and locking the navigation signals transmitted by the predetermined number of navigation satellites, the method further comprises:
 waiting for a predetermined locking delay interval that enables a lock established on the navigation signals transmitted by the predetermined number of navigation satellites to be refined; and   generating an indication that the predetermined number of navigation satellites have been acquired and that the navigation signals transmitted by the acquired navigation satellites have been locked after the predetermined locking delay interval expires.   
     
     
         3 . The method of  claim 1 , wherein the navigation parameters comprise at least one of the position of the navigation device, a velocity of the navigation device, and timing information associated with the navigation device. 
     
     
         4 . The method of  claim 1 , wherein said determining the position of the navigation device comprises:
 computing the position of the navigation device based on previously stored navigation data associated with the predetermined number of navigation satellites, wherein the previously stored navigation data comprises at least an almanac and ephemeris associated with the predetermined number of navigation satellites.   
     
     
         5 . The method of  claim 1 , wherein
 said acquiring and locking the navigation signals transmitted by the predetermined number of navigation satellites comprises providing a first control signal from a tracking unit of the navigation device to a measurement unit of the navigation device indicating that the predetermined number of navigation satellites have been acquired and that the navigation signals transmitted by the acquired navigation satellites have been locked; and   said initializing the positioning unit of the navigation device to determine the navigation parameters of the navigation device comprises providing a second control signal from the positioning unit to the measurement unit indicating that the positioning unit of the navigation device has been initialized to determine the navigation parameters of the navigation device.   
     
     
         6 . The method of  claim 5 , wherein each of said providing the first control signal and said providing the second control signal comprises one of transmitting a message, transmitting a voltage level on a physical wire, and setting a bit in a configuration register. 
     
     
         7 . The method of  claim 1 , wherein the predetermined number of navigation satellites comprises four or more navigation satellites. 
     
     
         8 . The method of  claim 1 , wherein if a vertical position of the navigation device is available, the predetermined number of navigation satellites comprises three navigation satellites. 
     
     
         9 . The method of  claim 1 , further comprising at least one of:
 providing the navigation parameters of the navigation device for presentation by the navigation device, and   determining a route to a destination based, at least in part, on the navigation parameters of the navigation device.   
     
     
         10 . The method of  claim 1 , further comprising:
 determining, at the navigation device, one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites,   wherein said determining the navigation parameters of the navigation device is based, at least in part, on the one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites.   
     
     
         11 . The method of  claim 10 , comprising:
 determining a first measurement time instant as a time instant when a first indication that the predetermined number of navigation satellites have been acquired and that navigation signals transmitted by the acquired navigation satellites have been locked and a second indication that the positioning unit of the navigation device has been initialized is received; and   generating a first pseudo-range measurement at the first measurement time instant.   
     
     
         12 . The method of  claim 1 , wherein:
 said acquiring and locking the navigation signals transmitted by the predetermined number of navigation satellites is prior to said initializing the positioning unit of the navigation device to determine the navigation parameters of the navigation device; or   said initializing the positioning unit of the navigation device to determine the navigation parameters of the navigation device is prior to said acquiring and locking the navigation signals transmitted by the predetermined number of navigation satellites.   
     
     
         13 . A network device comprising:
 a processor; and   a navigation unit coupled with the processor, the navigation unit configured to:
 acquire and lock navigation signals transmitted by a predetermined number of navigation satellites; 
 initialize a positioning unit of the navigation unit to determine navigation parameters of the network device; 
 determine, using the positioning unit, the navigation parameters of the network device based, at least in part, on the acquired and locked navigation signals; and 
 determine a position of the network device based, at least in part, on the navigation parameters. 
   
     
     
         14 . The network device of  claim 13 , wherein the navigation unit configured to acquire and lock the navigation signals transmitted by the predetermined number of navigation satellites comprises the navigation unit configured to:
 wait for a predetermined locking delay interval that enables a lock established on the navigation signals transmitted by the predetermined number of navigation satellites to be refined; and   generate an indication that the predetermined number of navigation satellites have been acquired and that the navigation signals transmitted by the acquired navigation satellites have been locked after the predetermined locking delay interval expires.   
     
     
         15 . The network device of  claim 13 , wherein the navigation unit operable to determine the navigation parameters of the navigation device comprises the navigation unit configured to:
 compute a position of the network device based on previously stored navigation data associated with the predetermined number of navigation satellites, wherein the previously stored navigation data comprises at least an almanac and ephemeris associated with the predetermined number of navigation satellites.   
     
     
         16 . The network device of  claim 13 , wherein the navigation unit is further configured to:
 provide the navigation parameters of the network device for presentation by the network device, and   determine a route to a destination based, at least in part, on the navigation parameters of the network device.   
     
     
         17 . The network device of  claim 13 , wherein the navigation parameters comprise at least one of the position of the network device, a velocity of the network device, and timing information associated with the network device. 
     
     
         18 . The network device of  claim 13 , wherein the navigation unit is further configured to:
 determine one or more pseudo-range measurements between the network device and each of the predetermined number of navigation satellites,   wherein the navigation unit is operable to determine the navigation parameters of the network device is based, at least in part, on the one or more pseudo-range measurements between the network device and each of the predetermined number of navigation satellites.   
     
     
         19 . One or more machine-readable storage media, having instructions stored therein, which, when executed by one or more processors causes the one or more processors to perform operations that comprise:
 acquiring and locking, at a navigation device, navigation signals transmitted by a predetermined number of navigation satellites;   initializing a positioning unit of the navigation device to determine the navigation parameters of the navigation device;   determining the navigation parameters of the navigation device based, at least in part, on the navigation signals transmitted by the predetermined number of navigation satellites; and   determining a position of the navigation device based, at least in part, on the navigation parameters.   
     
     
         20 . The machine-readable storage media of  claim 19 , wherein in response to said operation of acquiring and locking the navigation signals transmitted by the predetermined number of navigation satellites, the operations further comprise:
 waiting for a predetermined locking delay interval that enables a lock established on the navigation signals transmitted by the predetermined number of navigation satellites to be refined; and   generating an indication that the predetermined number of navigation satellites have been acquired and that the navigation signals transmitted by the acquired navigation satellites have been locked after the predetermined locking delay interval expires.   
     
     
         21 . The machine-readable storage media of  claim 19 , wherein said operation of determining the navigation parameters of the navigation device comprises:
 computing a position of the navigation device based on previously stored navigation data associated with the predetermined number of navigation satellites, wherein the previously stored navigation data comprises at least an almanac and ephemeris associated with the predetermined number of navigation satellites.   
     
     
         22 . The machine-readable storage media of  claim 19 , wherein the operations further comprise at least one of:
 presenting the navigation parameters at the navigation device, and   determining a route to a destination based, at least in part, on the navigation parameters of the navigation device.   
     
     
         23 . The machine-readable storage media of  claim 19 , wherein the operations further comprise:
 determining, at the navigation device, one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites,   wherein said operation of determining the navigation parameters of the navigation device is based, at least in part, on the one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites.   
     
     
         24 . A method comprising:
 determining that a predetermined number of navigation satellites have been acquired by a navigation device and that navigation signals transmitted by the acquired navigation satellites have been locked;   implementing a predetermined locking delay interval that enables a lock established on the navigation signals transmitted by the acquired navigation satellites to be refined;   determining that a positioning unit of the navigation device has been initialized; and   determining the navigation parameters of the navigation device for determining a position of the navigation device in response to determining that the predetermined number of navigation satellites have been acquired, the navigation signals transmitted by the acquired navigation satellites have been locked, and the positioning unit of the navigation device has been initialized.   
     
     
         25 . The method of  claim 24 , further comprising:
 generating an indication that the predetermined number of navigation satellites have been acquired and that the navigation signals transmitted by the acquired navigation satellites have been locked after the predetermined locking delay interval expires.   
     
     
         26 . The method of  claim 24 , wherein the navigation parameters comprise at least one of a position of the navigation device, a velocity of the navigation device, and timing information associated with the navigation device. 
     
     
         27 . The method of  claim 24 , further comprising:
 determining, at the navigation device, one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites,   wherein said determining the navigation parameters of the navigation device is based, at least in part, on the one or more pseudo-range measurements between the navigation device and each of the predetermined number of navigation satellites.   
     
     
         28 . The method of  claim 27 , comprising:
 determining a first measurement time instant as a time instant when a first indication that the predetermined number of navigation satellites have been acquired and that navigation signals transmitted by the acquired navigation satellites have been locked and a second indication that the positioning unit of the navigation device has been initialized is received; and   generating a first pseudo-range measurement at the first measurement time instant.