From traced lines
to named room polygons.

A closed line is not automatically a room.

MapNib traces visible raster strokes as GeoJSON LineString features. A wall drawn with two edges can produce two lines, and labels or furniture can also be traced. Even a closed traced line remains linework until you deliberately create an area.

Use Add polygon to draw a room boundary, place at least three distinct corners, then finish the polygon. Review the shape and its relationship to adjoining rooms. Current polygons support one exterior ring; holes and crossing edges are not supported.

Room polygons are created and reviewed by you. MapNib does not automatically recognize rooms, infer wall thickness, or construct a routing network.

Carry useful room information with the geometry.

Named room polygons include these properties in the exported GeoJSON:

• roomId — the room identifier, stable within its project.
• name — the room name you provide.
• roomType — the type you select in the editor.
• areaM2 — area in square metres, calculated from the calibrated scale.
• perimeterM — perimeter in metres, calculated from the calibrated scale.

A destination application can read these properties, but how they appear depends on that application’s styling and data handling. Exporting a name does not guarantee that another tool will display it as a label.

Review the boundaries and the scale.

Measurements change when you edit the geometry or calibration. Check that room boundaries represent the area you intend to measure and that adjacent rooms do not unintentionally overlap.

For an illustrative 4-by-5-metre rectangle, the area is 20 square metres and the perimeter is 18 metres. If the scale is wrong, both results will be wrong: doubling all lengths doubles the perimeter and quadruples the area.

Estimated calibration remains estimated. Measurements are not survey-certified. Read the scale and placement guide ↗

Inspect the FeatureCollection before using it.

A saved export can contain both LineString and Polygon features. Coordinates use WGS 84 longitude first, latitude second. Original image bytes and editing history are not embedded in the GeoJSON.

• Check that your destination supports the geometry types and preserves the properties you need.
• Inspect room names, types, boundaries, and measurements after import.
• Verify placement against a trusted reference rather than relying only on a successful import.

The downloadable sample contains nine synthetic linework features with estimated scale at 0°, 0°. It illustrates a linework FeatureCollection; it does not contain named room polygons or represent a real building. Try manually drawing a polygon in the interactive demo to explore polygon geometry.

Create and name room polygons in your workspace, then include their properties in your GeoJSON export. Explore the workspace ↗