AutoBar
The AutoBar provided with the V-STARS system is a fixture with five targets arranged in the form of a cross. The target's known coordinates are used by GSI's AutoStart procedure to determine the camera's orientation relative to the AutoBar. The AutoBar is securely attached on or near the measured object, preferably in a highly visible location. The AutoBar's default coordinate system has its origin at target1 at the bottom of the AutoBar. The positive Z axis goes thru point 3 at the top of the bar. The positive X axis is up out of the AutoBar.

AutoStart
The procedure used in V-STARS to get the preliminary orientation (location and aiming) of each photograph taken in a measurement. In order to AutoStart , one must merely measure four target points with known X, Y, Z coordinates. The only requirement is that the four points should not lie on a line. AutoStart is often used in conjunction with the AutoBar provided with the V-STARS system to make measurements fast, easy and automatic.
CMM
Abbreviation for Coordinate Measuring Machine. A widely used family of machines that make 3 dimensional measurements of objects. Typically, the machine has a head with a measuring tip attached to it that can be moved around in a 3-dimensional space (usually the head is attached to rails and a gantry. The location of the head is encoded so that everywhere it touches the object the 3-dimensional coordinates are measured.

Coded targets
Coded targets consist of a central circle surrounded by a pattern of squares. The different pattern of squares around each target uniquely identifies that target. When used properly, coded targets allow measurements to be done completely automatically.

Coded target nuggets
Coded target nuggets are the square that surround the central dot in a coded target.

Driveback
When approximate coordinates are available for all or some of the target points on a measurement, they can be measured automatically. After the photograph is oriented (using the AutoStart or SuperStart procedures), V-STARS converts all X,Y,Z target coordinates into predicted x,y image coordinates and then searches for the target in that area.

Field of View
The camera's field of view defines how much it sees and is a function of the focal length of the lens and the size (often called the format) of the digital sensor. For a given lens, a larger format sensor has a larger field of view. Similarly, for a given size sensor, a shorter focal length lens has a wider field of view.

Focusing
The range of acceptable sharpness is called the depth of focus. The depth of focus of a lens is a function of many factors, including: the focal length of the lens, the format size, the distance from the camera to the object, the size of the object, and the f-number of the lens.

V-STARS has been designed so that images will be in acceptable focus for points between 0.5 meters (20 inches) and 60 meters (200 feet) from the camera. Fixing the focus effectively eliminates the depth of focus problem.

F-number
The F-number is the ratio of the lens focal length to the diameter of the lens iris. The f-number provides an indication of the light sensitivity of the lens. The lower the f-number, the more light sensitive the lens is. However, lower f-numbers also reduce the depth of focus.

Flash Synchronization
The camera's flash must fire at the same time that the camera's shutter is completely open or else the retro-reflective targets will not be exposed.

Free-format
Free-format fields do not have to occupy any particular columns of the record. Each field simply must end with a blank or comma or tab character. A free-format field may also have any number of leading blanks.

Orientation
Orientation is the term used for the cameras position and aiming in space. The orientation of a camera is defined by its coordinates (X,Y,Z) and by its aiming direction (defined by three angles). GSI's AutoStart and Resection procedures are used to accurately determine the camera's orientation.

Photogrammetry
Photogrammetry, as its name implies, is a 3-dimensional coordinate measuring technique that uses photographs as the fundamental medium for metrology (or measurement). Photography describes the photographic principles involved in photogrammetry, while Metrology describes the techniques for producing 3-dimensional coordinates from two-dimensional photographs.

Resection
Resection is the procedure used to get the final position and aiming (called the orientation) of the camera when a picture is taken. Typically all the points that are seen and known in XYZ in the image are used to determine this orientation.

Retro-reflective
A property which causes light to be reflected very efficiently back to the light source. The retro-reflective targets used by V-STARS act much like highway reflectors but are much more efficient. By using a low-powered flash located at the camera to illuminate the targets, the resulting target images are very bright and easy to find and measure.

RMS
Root-Mean-Square - a statistical measure of the dispersion or spread of a group of data. The name comes from the fact that the RMS is equal to the square Root of the Mean (average) of the sum of Squares of the values in the data set. With regards to resections, the RMS provides a measure of the quality of the resection.

Scale bar
A fixture that has two or more targets with known distances. The distance(s) between the target(s) are used to scale the measurement.

SuperStart
The SuperStart command will open the picture and complete the following processes:

1) Scan image for potential targets
2) Determine whether an AutoBar is present
3) Identify any codes that are present.
4) Use the known (coordinated) coded targets and AutoBar found to determine the location in space (resection) of the image.
5) Driveback to any points in the Driver file.

Theodolite
A precise angle measuring instrument. It consists of a sighting telescope which can be moved in azimuth and elevation. The azimuth and elevation angels are very precisely encoded. Using two widely separated instruments operators can sight through the telescopes on a common point and produce the 3-dimensional coordinates of the point by triangulation.

XYZ File
Each record of an XYZ file has a valid Point Label followed by the point's X, Y and Z coordinates. Sometimes, accuracy estimates for the point in X,Y and Z may also be included, but these are not used by V-STARS. The format for an XYZ file is shown below.