<!-- GENERATED by tools/generators/itemDocsEmitter.py from definitions/ - do not edit -->
```{raw} latex
\clearpage
```

(sec-item-sensormarker)=
# SensorMarker

A sensor attached to a marker, which measures what the marker provides, in the current configuration.

## Parameters

The parameters of the item; in a dictionary, its type is 'Marker':

| name | type | size | default | description |
|---|---|---|---|---|
| **name** | String |  | '' | sensor's unique name |
| **markerNumber** | MarkerIndex |  | invalid (-1) | marker number to which sensor is attached to |
| **writeToFile** | Bool |  | True | True: write sensor output to file; flag is ignored (interpreted as False), if fileName='' |
| **fileName** | String |  | '' | directory and file name for sensor file output; empty: no file is written; a relative name is placed in `exudyn.config.outputDirectory` if that is set; the directory is created if it does not exist |
| **outputVariableType** | OutputVariableType |  | OutputVariableType::_None | OutputVariableType for sensor; output variables are only possible according to markertype, see general description of SensorMarker |
| **storeInternal** | Bool |  | False | true: store sensor data in memory (faster, but may consume large amounts of memory); false: internal storage not available |
| **visualization** | VSensorMarker |  |  | parameters for visualization of item |

## Visualization parameters

The parameters of `VSensorMarker`, given as `visualization`:

| name | type | size | default | description |
|---|---|---|---|---|
| **show** | Bool |  | True | set true, if item is shown in visualization and false if it is not shown |

## Drawing

Drawn as [all sensors](#sec-drawing-sensors).
(description-sensormarker)=
## Detailed description

### Attached to

The marker `markerNumber`, any kind of marker.

### Measures

What the marker provides, which depends on its types; the coordinates only in the **current** configuration:

| the marker provides | `outputVariableType` can be |
|---|---|
| a position (`MarkerBodyPosition`, `MarkerNodePosition`, ...) | `Position`, `Displacement`, `Velocity` |
| an orientation (`MarkerBodyRigid`, `MarkerNodeRigid`, ...) | in addition `RotationMatrix`, `Rotation`, `AngularVelocity`, `AngularVelocityLocal`, `HomogeneousTransformation` |
| coordinates (`MarkerNodeCoordinate`, `MarkerNodeCoordinates`, ...) | `Coordinates`, `Coordinates_t` |
| a relative coordinate of two bodies | `Coordinates`, `Coordinates_t` |

Markers have no output variables of their own, which is why this sensor lists them here.

(miniexample-sensormarker)=
## Mini example


```python
#what a marker provides, here the velocity of a point of a body
node = mbs.AddNode(NodePoint(referenceCoordinates=[0,0,0], initialVelocities=[0,2,0]))
body = mbs.AddObject(ObjectMassPoint(nodeNumber=node, mass=1))
mBody = mbs.AddMarker(MarkerBodyPosition(bodyNumber=body, localPosition=[0,0,0]))
mbs.AddLoad(LoadForceVector(markerNumber=mBody, loadVector=[0,-1,0]))
sVelocity = mbs.AddSensor(SensorMarker(markerNumber=mBody, outputVariableType=exu.OutputVariableType.Velocity,
                                       storeInternal=True, writeToFile=False))

mbs.Assemble()
mbs.SolveDynamic()

#v = v0 + F/m*t at t=1
exu.sys['testResult'] = mbs.GetSensorValues(sVelocity)[1] #1
```


Examples (Ex) and TestModels (TM) that show this item, with weblink to github: [`plotSensorTest.py`](https://github.com/jgerstmayr/EXUDYN/blob/master/python/TestModels/plotSensorTest.py) (TM), [`pendulumFriction.py`](https://github.com/jgerstmayr/EXUDYN/blob/master/python/TestModels/pendulumFriction.py) (TM)