Navigation based on downward facing sensors

1. A method, comprising:

obtaining sensor information from a downward facing sensor coupled to an aircraft; and

determining a new position using the sensor information, including by:

obtaining directional information associated with the aircraft's direction of flight;

obtaining a previous position associated with the aircraft;

filtering a plurality of datasets in a ground feature database using the directional information and the previous position in order to obtain a reduced group of datasets, wherein each dataset in the ground feature database is associated with a known in-air position; and

comparing the sensor information against the reduced group of datasets in order to determine the new position.

2. The method recited in claim 1 , wherein:

the downward facing sensor includes a Lidar system; and

each dataset in the ground feature database is associated with Lidar topographical data taken from a known in-air position.

3. The method recited in claim 1 , wherein obtaining the directional information includes:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings.

4. The method recited in claim 1 , wherein obtaining the directional information includes:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings, including by:

determining if the aircraft's latitude is expected to decrease, remain constant, or increase;

determining if the aircraft's longitude is expected to decrease, remain constant, or increase; and

determining if the aircraft's altitude is expected to decrease, remain constant, or increase.

5. The method recited in claim 1 , wherein:

obtaining the sensor information includes receiving, at a position estimator, the sensor information from the aircraft;

determining the new position includes determining, at the position estimator, the new position, wherein the position estimator accesses the reduced group of datasets from the ground feature database; and

the method further includes sending, from the position estimator to the aircraft, the new position.

6. A system, comprising:

a processor; and

a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions which when executed cause the processor to:

obtain sensor information from a downward facing sensor coupled to an aircraft; and

determine a new position using the sensor information, including by:

obtaining directional information associated with the aircraft's direction of flight;

obtaining a previous position associated with the aircraft;

filtering a plurality of datasets in a ground feature database using the directional information and the previous position in order to obtain a reduced group of datasets, wherein each dataset in the ground feature database is associated with a known in-air position; and

comparing the sensor information against the reduced group of datasets in order to determine the new position.

7. The system recited in claim 6 , wherein:

the downward facing sensor includes a Lidar system; and

each dataset in the ground feature database is associated with Lidar topographical data taken from a known in-air position.

8. The system recited in claim 6 , wherein the instructions for obtaining the directional information include instructions for:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings.

9. The system recited in claim 6 , wherein the instructions for obtaining the directional information include instructions for:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings, including by:

determining if the aircraft's latitude is expected to decrease, remain constant, or increase;

determining if the aircraft's longitude is expected to decrease, remain constant, or increase; and

determining if the aircraft's altitude is expected to decrease, remain constant, or increase.

10. The system recited in claim 6 , wherein:

the instructions for obtaining the sensor information include instructions for receiving, at a position estimator, the sensor information from the aircraft;

the instructions for determining the new position include instructions for determining, at the position estimator, the new position, wherein the position estimator accesses the reduced group of datasets from the ground feature database; and

the memory is further configured to provide the processor with instructions which when executed cause the processor to send, from the position estimator to the aircraft, the new position.

11. A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:

obtaining sensor information from a downward facing sensor coupled to an aircraft; and

determining a new position using the sensor information, including by:

obtaining directional information associated with the aircraft's direction of flight;

obtaining a previous position associated with the aircraft;

filtering a plurality of datasets in a ground feature database using the directional information and the previous position in order to obtain a reduced group of datasets, wherein each dataset in the ground feature database is associated with a known in-air position; and

comparing the sensor information against the reduced group of datasets in order to determine the new position.

12. The computer program product recited in claim 11 , wherein:

the downward facing sensor includes a Lidar system; and

each dataset in the ground feature database is associated with Lidar topographical data taken from a known in-air position.

13. The computer program product recited in claim 11 , wherein the computer instructions for obtaining the directional information include computer instructions for:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings.

14. The computer program product recited in claim 11 , wherein the computer instructions for obtaining the directional information include computer instructions for:

receiving one or more control settings associated with steering the aircraft; and

determining the directional information based at least in part on the control settings, including by:

determining if the aircraft's latitude is expected to decrease, remain constant, or increase;

determining if the aircraft's longitude is expected to decrease, remain constant, or increase; and

determining if the aircraft's altitude is expected to decrease, remain constant, or increase.

15. The computer program product recited in claim 11 , wherein:

the computer instructions for obtaining the sensor information include computer instructions for receiving, at a position estimator, the sensor information from the aircraft;

the computer instructions for determining the new position include computer instructions for determining, at the position estimator, the new position, wherein the position estimator accesses the reduced group of datasets from the ground feature database; and

the computer program product further includes computer instructions for sending, from the position estimator to the aircraft, the new position.