While waiting for my M4 (#1238) I’ve been following others’ experiences and have become particularly interested in the calibration process and its artifact, the coordinate system.

I’m going to apologize in advance for what will be a somewhat long post, and note that I don’t think that any of this is going to solve any problems- so feel free to ignore it and work on important things…

As I understand it, the initial values entered in maslow.yaml do two things- set the process used based on a vertical or horizontal orientation, and the area to the used for the calibration. This second process takes a rectangle defined by four X,Y coordinate points that represent the nominal locations of the anchor points-

- Bottom Left (BLX, BLY)
- Bottom Right (BRX,BRY)
- Top Left (TLX, TLY)
- Top Right (TRX, TRY)

and then offsets each side ‘inward’ by the calibration offset to define a smaller area for the calibration.

So far, so good.

All the examples I have seen follow this same pattern, but it leads to some questions-

- Since the default frame size is 8x10 for a 4x8 (I apologize to the rest of the world for the choice of units…) workspace, is the same calibration offset always used for the X and Y directions?
- Is there any advantage to intentionally setting the initial anchor point in a manner that will yield a calibration area equal to the intended workspace?
- Since the four anchors can be explicitly defined, do they have to form a rectangle?
- For example, if the anchors are intentionally arranged in a trapezoid, can or should it be defined thus for calibration?

In every example I have seen, the bottom left anchor is always defined as the origin (BLX=0,BLY=0) and the X axis passes through the bottom left and bottom right anchors (BRY=0) and the results of the calibration process appear to always generate results that conform to this- including potentially having negative coordinate values. In particular, here-

@bar only reported the non-zero values, which appears to confirm that they are essentially fixed.

- Is this always the case?
- Is the bottom left anchor always the origin?
- Does the X axis always pass through the two bottom anchors?
- Assuming that the above is true, does this mean that the edge a panel to be machined must be set exactly parallel to this X axis line?

Also, there has been many comments that the dimensions of the anchors and the workspace can be expanded or shrunk from the default 4x8, but in every case it appears that the space is defined as a rectangle with the longer side on the X axis (landscape) -or a square.

- Can the longer axis be on the Y axis (portrait)?

Lastly, the fitness result appears to relate to how well the calculated anchor locations correlate to (or deviate from) the full set of test points.

- Is this a dimensionless measure on a scale of 0 to 1?
- Is there any reasonable way to calculate some real world accuracy metric from this value?