Coordinate Systems

Unaligned Coordinates

Unaligned sensors use sensor coordinates, that is, the coordinate system is relative to the sensor itself. The measurement range (MR) is along the Z axis. The sensor’s field of view (FOV) is along the X axis. Most importantly, the origin is at the center of the measurement range and field of view, in other words, the center of the scan area.

The Y axis represents the relative position of the target part in the direction of travel. Y position increases as the target moves forward (increasing encoder position). Typically, the direction of travel of the target is opposite the sensor's positive Y axis. If it isn't (due to the orientation of the sensor's mounting), you need to configure the sensor's orientation to be "reversed." For more information, see Creating a Sensor System.

Aligned Coordinates

Understanding aligned coordinates is important for two reasons. First, they are the direct result of performing the built-in alignment procedure. Second, they change how scan data is represented and how measurement results should be interpreted. For more information on aligning sensors, see Aligning Sensors.

The adjustments resulting from alignment are called transformations (offsets along the axes and rotations around the axes). Transformations are displayed in the System > Alignment page. Note that currently, you can ignore Sensor Group Transforms, which represent the transformations between groups of sensors; support for this will be available in future versions of the sensor software. For more information on transformations in the web interface, see Transformations.

In aligned coordinates, the X axis is parallel to the alignment target surface. The system Z origin is set to the base of the alignment target object. In both cases, alignment determines the offsets in X and Z.

Alignment is used with a single sensor to compensate for mounting misalignment and to set a zero reference, such as a conveyor belt surface.

Alignment can also determine offsets along the Y axis. This allows setting up a staggered layout in multi-sensor systems. This is especially useful in side-by-side mounting scenarios, as it provides full coverage for models with a small scan area.

As with sensor coordinates, in system coordinates, Y position increases as the object moves forward (increasing encoder position).

Alignment also determines the Y Angle (angle on the X–Z plane, around the Y axis) needed to align sensor data. This is also sometimes called roll correction.

Y angle is positive when rotating from positive X to positive Z axis.

Similarly, tilt can be determined around the Z and the X axis, which compensates for the angle in height measurements. These are sometimes called yaw correction and pitch correction, respectively. Intentional rotation around the X axis is often used for specular mounting, that is, for scanning targets that are shiny or reflective. Note however that X angle correction can't currently be corrected for using the alignment procedure available on the Alignment panel. X angle can only be manually entered in the Transformations panel. For more information on transformations in the web interface, see Transformations.

X angle is positive when rotating from positive Y to positive Z. Z angle is positive when rotating from positive X to positive Y.

When applying the transformations, the data is first rotated around X (clockwise, with the X axis toward the viewer), then Y (counterclockwise), and then Z (clockwise), and then the offsets are applied.