# Touch

Cartographer can make use of the eddy current to repeatably measure the distance from the bed to the probe. By observing this, we are able to stop as soon as the nozzle touches the bed, as the distance will stop decreasing.

## Touch homing

Use `CARTOGRAPHER_TOUCH_HOME` in your start print to home your printer using Survey Touch. Make sure your nozzle is below 150 degrees and make sure your bed is level.

## Measuring touch accuracy

We can check the accuracy of the touch by running `CARTOGRAPHER_TOUCH_ACCURACY`.\
This will run a few touches and output some statistics, like seen below.

> touch accuracy results: maximum -0.063035, minimum -0.065535, range 0.002500, average -0.064035, median -0.063660, standard deviation 0.000848 median absolute deviation 0.000625

## Bed mesh calibrate

{% hint style="danger" %}
Touch Mesh not currently implemented
{% endhint %}

We support touching the bed to calibrate a bed mesh. This can be useful especially to discover probe bias or problem sections of the bed. We can compare the touched mesh to the one generated by scan.

{% hint style="info" %}
Remember to adjust probe count. Executing 400 touches takes a long time.
{% endhint %}

Run `BED_MESH_CALIBRATE METHOD=touch PROBE_COUNT=5,5` 

Cartographer will automatically adjust the mesh boundaries based on your configuration, to ensure your nozzle and probe are not off the bed.

> Updating MESH\_MIN from config value (13.0, 11.0) to (13.0, 28.74)\
> Updating MESH\_MAX from config value (215.0, 206.0) to (214.72, 206.0)


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