> ## Documentation Index
> Fetch the complete documentation index at: https://support.lumafield.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Position

> GD&T true position of a hole against its nominal CAD cylinder

Position constrains how far a hole's axis may stray from its true position on the CAD model. In ASME Y14.5 the position tolerance is a diametral zone: a cylinder, centered on the true position, that the axis must stay inside. Voyager evaluates that zone for a scanned cylinder against the matching cylinder on the nominal CAD, in a datum reference frame.

Position is in the Toolbar in [Dimensioning Mode](/voyager/voyager-modes#dimensioning-mode).

Position is a location control, not a form control. [Cylindricity](/voyager/voyager-cylindricity) asks whether the hole is round and straight. Position asks whether that hole is in the right place relative to the datums and the CAD. The tolerance is always a diameter. The panel labels it **Tolerance ⌀**.

<h2 id="what-you-need-first">
  What you need first
</h2>

* A [Feature Set](/voyager/voyager-feature-extraction) that includes the hole as a cylinder.
* A nominal `.STEP` file that has finished processing. See [Nominal CAD Import](/voyager/voyager-nominal-import).
* Datums that can locate the hole. A Frame for Position needs a **primary** datum. **Secondary** and **tertiary** are optional. See [Datum Definition](/voyager/voyager-datums#frames).
* An [Alignment](/voyager/voyager-alignment) when you want Voyager to match the CAD cylinder for you. Without an alignment you pick the CAD cylinder yourself.

<h2 id="workflow">
  Workflow
</h2>

<Steps>
  <Step title="Select Position">
    Choose **Position** from the Toolbar, or right-click the scan cylinder and choose **Add position control…**.
  </Step>

  <Step title="Select the scan and the CAD">
    Pick the volume to measure and the nominal CAD. CAD that is still processing, or that failed, is listed but cannot be selected.
  </Step>

  <Step title="Pick the two cylinders">
    Select the **Scan cylinder**, then the **CAD cylinder** whose axis is the true position. If the scan is aligned, Voyager marks a lined-up CAD cylinder as **matched**. If nothing lines up, click the CAD cylinder in the CAD view.
  </Step>

  <Step title="Select the datums">
    Pick the datums that constrain the position, primary first. Click a datum callout or choose one for each rank. A linked frame fills the other side when the scan and CAD are aligned and the datums are linked.
  </Step>

  <Step title="Set the tolerance and submit">
    Enter **Tolerance ⌀** in millimeters and submit. The result is a callout on the hole. Drag the leader to place it.
  </Step>
</Steps>

<h2 id="reading-the-result">
  Reading the result
</h2>

The callout reports the position of the scanned axis against the true position, and whether that deviation is inside the diametral zone. **Measured in** names the Frame. When the frame can sit in more than one place — datum shift — **Frame** steps through the candidates. **Open freedoms** lists the degrees of freedom the datums did not stop. **None** means the frame fully locates the hole.

The tolerance can be edited after the control exists. The pass or fail state updates without a new extraction.

<h2 id="related-pages">
  Related pages
</h2>

* [Alignment](/voyager/voyager-alignment)
* [Datum Definition](/voyager/voyager-datums)
* [Cylindricity](/voyager/voyager-cylindricity)
* [Perpendicularity](/voyager/voyager-perpendicularity)
* [Parallelism](/voyager/voyager-parallelism)
* [Profile](/voyager/voyager-profile)
* [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning)
* [Voyager Release Notes](/platform/voyager-release-notes)


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