The present invention relates generally to methods and apparatus for performing angular measurements. Merely by way of example, embodiments of the present invention provide methods for acquiring high resolution angular measurements using images. Such measurements may be used, for example, in surveying applications. However, the scope of embodiments of the present invention is broader than this particular application and can be applied to other applications utilizing angular measurements.
The art of surveying involves the determination of unknown positions using measurements of angles and distances. For example, in some surveying operations horizontal and vertical angles and distance are measured between reference and target points. In other surveying operations, horizontal and vertical angles are measured between more than one reference point and a target point. In either case, the measured data may be used to calculate the position of the target point.
A theodolite is a surveying instrument that is commonly used to measure horizontal and vertical angles. A theodolite typically includes a telescope mounted so that it can be rotated about horizontal and vertical axes. A theodolite may include circular scales that are used in measuring the angular position of the telescope. The horizontal angle (e.g. yaw) and the vertical angle (e.g. pitch) are read from the circular scales to determine the yaw and pitch of the target with respect to a reference point. Some modern electronic theodolites utilize angle encoders instead of scales to automate angular measurements.
Despite the utility of theodolites, improved methods and apparatus for acquiring angular measurements are desired.