Help CalcGrid
The CalcGrid button uses FireSight matchTemplate
to find grid intersections from which it tries to infer the dimensions of an infinite grid that matches the intersections found.
If successful, CalcGrid will return the following statistics:
- origin provides the x and y coordinates of the intersection closest to the image center
- angle is the clockwise positive angle in degrees of the grid from horizontal
- cellSize gives the pixel width and height of each cell in the grid
Verify Z-plane flatness. If the camera is within 20mm of the printable calculation grid, the cellSize should be uniform for all images taken in the same Z-plane.
Measure camera angle If the grid is exactly lined with the direction of motion, the grid angle will be the camera angle.
Measure camera resolution Divide the imaged cell size in pixels by the actual cell size to determine pixels/mm at any Z-height.
Origin can be used to measure the accuracy of extremely fine motion. For example, measurements taken at each of the four corners of a 1mm-square path would verify how well the actual path conformed to the planned path.
Grid matching works best with more cells rather than fewer. If there are not enough cells, the grid metrics become less accurate to the point of failure. As best practice, take multiple measurements and compare results, rejecting outliers.
Align the camera and grid as closely as possible so that the gridlines are vertical/horizontal. The grid matching algorithm is very sensitive and fails if the grid isn't aligned to the camera image.
The CalcGrid button uses FireSight matchTemplate
to match grid line intersections using cross32.png.
This template is useful in that it matches grids of all sizes.
In particular the template works well with the printable calculation grid.
