Systems and methods for northfinding

1. An apparatus for target location, comprising:

a portable housing comprising:

a range sensor to generate range data;

an image sensor to generate image data;

an inertial sensor to generate inertia data; and

a processor to:

receive the image data from the image sensor and determine a first orientation of the housing; and

receive the inertia data from the inertial sensor and modify the first orientation based on the inertia data to produce a modified orientation of the housing;

wherein the image data comprises data indicative of at least one celestial body and when the processor determines the first orientation, the processor compares the image data to known parameters for the at least one celestial body at a given time of day and the location indicated by the housing location data to determine the first orientation;

wherein the celestial body comprises at least one selected from the group consisting of: the sun, the moon, one star other than the sun, a grouping of stars other than the sun, and one or more planets; and

wherein the celestial body comprises the sun including a center and a solar disc, and the processor is further configured to:

 generate binned image data based on the image data and applying a predetermined threshold;

 perform a Hough circle transformation on the binned image data, wherein a radius search value of the transformation comprises a pixel value corresponding to an expected radial size of the solar disc; and

 identify a result of the Hough circle transformation as the location of the center of the sun.

2. The apparatus of claim 1 wherein the processor receives the housing location data from one selected from the group consisting of: a global positioning system (GPS) sensor external to the housing, a GPS sensor internal to the housing, and a user input device.

3. The apparatus of claim 1 wherein the range sensor comprises a laser rangefinder.

4. The apparatus of claim 1 wherein the inertial sensor comprises a MEMS gyroscope.

5. The apparatus of claim 1 wherein the image data comprises data indicative of a body having a known location and when the processor determines the first orientation, the processor compares the location indicated by the housing location data and the known location of the body.

6. The apparatus of claim 1 wherein the processor is further configured to:

receive the range data from the range sensor and housing location data; and

determine the target location based on the modified orientation data, the range data, and the housing location data.

7. A method for target location using a portable housing, comprising:

receiving image data from an image sensor in the housing and determining a first orientation of the housing; and

receiving inertia data from an inertial sensor in the housing and modifying the first orientation based on the inertia data to produce a modified orientation of the housing;

wherein the image data comprises data indicative of at least one celestial body and the method further comprises:

comparing the image data to known parameters for the at least one celestial body at a given time of day and the location indicated by the housing location data to determine the first orientation;

wherein the celestial body comprises at least one selected from the group consisting of: the sun, the moon, one star other than the sun, a grouping of stars other than the sun, and one or more planets; and

wherein the celestial body comprises the sun including a center and a solar disc, and the method further comprises:

 generating binned image data based on the image data and applying a predetermined threshold;

 performing a Hough circle transformation on the binned image data, wherein a radius search value of the transformation comprises a pixel value corresponding to an expected radial size of the solar disc; and

 identifying a result of the Hough circle transformation as the location of the center of the sun.

8. The method of claim 7 further comprising:

receiving range data from a range sensor in the housing and housing location data; and

determining the target location based on the modified orientation data, the range data, and the housing location data.

9. The method of claim 7 wherein the image data comprises data indicative of a body having a known location and the method further comprises determining the first orientation by comparing the location indicated by the housing location data and the known location of the body.

10. A non-transitory computer-readable medium comprising instructions that, when executed by a processor, cause the processor to:

receive image data from an image sensor and determine a first orientation of a portable housing for the processor; and

receive inertia data from an inertial sensor and modify the first orientation based on the inertia data to produce a modified orientation of the housing;

wherein the image data comprises data indicative of at least one celestial body and the instructions further cause the processor to:

compare the image data to known parameters for the at least one celestial body at a given time of day and the location indicated by the housing location data to determine the first orientation;

wherein the celestial body comprises at least one selected from the group consisting of: the sun, the moon, one star other than the sun, a grouping of stars other than the sun, and one or more planets; and

wherein the celestial body comprises the sun including a center and a solar disc, and the instructions further cause the processor to:

 generate binned image data based on the image data and applying a predetermined threshold;

 perform a Hough circle transformation on the binned image data, wherein a radius search value of the transformation comprises a pixel value corresponding to an expected radial size of the solar disc; and

 identify a result of the Hough circle transformation as the location of the center of the sun.

11. The non-transitory computer-readable medium of claim 10 wherein the instructions further cause the processor to:

receive range data from a range sensor and housing location data; and

determine a location of a target based on the modified orientation data, the range data, and the housing location data.

12. The non-transitory computer-readable medium of claim 10 wherein the image data comprises data indicative of a body having a known location and the instructions further cause the processor to determine the first orientation by comparing the location indicated by the housing location data and the known location of the body.