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

# Coordinates and units

> Metres for the model, millimetres for paper, pixels only for the screen.

Floorkit uses three kinds of numbers. Keep them apart and your geometry is always in the correct place.

| Space | Coordinates | Unit |
| - | - | - |
| Model | `[x, y, z]`, the Y axis is up | Metres |
| Plan | `[x, z]`, seen from above | Metres |
| Paper | `{ x, y }` from the top-left corner of the sheet | Millimetres |
| Screen | Pointer and canvas positions | Pixels |

## Heights come from the storey

A storey has an `elevation`. This is the only height in the model that is measured in the world. Each element in the storey gives its height as an offset from that elevation.

| Field | Measured from |
| - | - |
| Storey `elevation` | The world zero |
| Slab `baseOffset` | The storey elevation, to the bottom of the slab |
| Roof `baseOffset` | The storey elevation, to the eave |
| Column `baseOffset` | The storey elevation, to the base |
| Door `baseHeight` | The base of its wall |
| Window `sillHeight` | The base of its wall, to the bottom of the glass |
| Railing `path` | The world zero. Each point is `[x, y, z]`. |

Example: a storey has `elevation: 3.2`. A slab in it has `baseOffset: 0.1`. The bottom of the slab is at 3.3 metres.

## Positions along a wall

The `offset` of a door or a window is a distance along its wall. It starts at the first point of the wall and follows each segment. On a closed wall, it also follows the last segment back to the first point.

## Angles

| Field | Unit | Direction |
| - | - | - |
| `yawDeg` of a free opening | Degrees | Zero points to +X. A positive angle turns to +Z. |
| Roof `pitch` | Degrees | The slope of the roof |
| Stair `rotation` | Degrees | Counter-clockwise, seen from above |

## Drawing scale

A viewport on a sheet has a `scale`. The scale is paper size divided by real size.

| Scale | `scale` value | One metre on paper |
| - | - | - |
| 1:50 | `0.02` | 20 mm |
| 1:100 | `0.01` | 10 mm |
| 1:200 | `0.005` | 5 mm |

## Pointer positions

A pointer position is in pixels. Change it to model metres before you make an edit command. The [plan editor](/floorkit/guides/add-a-plan-editor) and the [3D editor](/floorkit/guides/add-a-3d-editor) do this for you.

## Next

<CardGroup cols={2}>
  <Card title="Editing and history" icon="clock-rotate-left" href="/floorkit/concepts/editing-and-history">
    Learn how an edit changes the model.
  </Card>

  <Card title="Views and sheets" icon="compass-drafting" href="/floorkit/concepts/drawings">
    Learn how the model becomes a drawing.
  </Card>
</CardGroup>


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