Densify

Add vertices so no segment exceeds a meter-honest max length via PostGIS ST_Segmentize on geography. Attributes are kept.

basic

A densify step adds intermediate vertices along input lines and polygon boundaries so no segment exceeds the chosen max length. It uses PostGIS ST_Segmentize on geography, so spacing is meter-honest on Earth regardless of latitude. Attributes are copied from the source row.

Use before a reprojection (to keep curves looking smooth after a CRS change), for smoother along-line sampling, or as a preprocess for fishnet / vertices work on long thin features. Point-only input is an effective no-op (a point has no segments).

Inputs

  • Source layer. Any geometry type. Null geometries are skipped.
  • Max segment length. A number that converts to at least 1 meter.
  • Unit. Meters, feet, kilometers, or miles. The server converts to meters before calling ST_Segmentize on geography. Soft ceiling: 100 km (same as Buffer / Simplify) so a tiny misclick cannot spawn millions of vertices.

Output

One row per non-null input geometry:

  • Geometry: the input with extra vertices on edges longer than the max segment length (bbox unchanged).
  • Properties: copied from the source row.

How to use it on its own

From Analyze (guided)

  1. Open a data layer and switch to the Analyze tab.
  2. Click Densify this layer.
  3. Enter the max segment length and unit.
  4. Optionally edit the title.
  5. Click Create derived layer.

The portal creates a private derived layer and opens it. Expect a short server job, not an instant browser result. Meter-honest segment length runs on PostGIS — Analyze does not invent an in-browser densify.

From the new-item wizard

  1. New-item wizard → Derived layer.
  2. Pick a Source.
  3. Add a Densify step.
  4. Enter max segment length and unit.
  5. Save.

Examples

  • Smoother roads after reproject. Source: long highway centerlines. Max segment: 50 meters. Output: the same roads with vertices dense enough that a later projected view does not look like a chorded polyline.
  • Along-line samples. Source: survey transects. Max segment: 10 meters. Output: denser vertices for interpolation or fishnet prep.

Notes

  • Min 1 m / max 100 km. The generator refuses shorter or longer max segment lengths after unit conversion.
  • Geography, not planar degrees. Length is interpreted in meters on the spheroid; do not enter "degree" values.
  • Does not change the envelope. Vertices are inserted on existing edges only; the bounding box stays the same.
  • Pairs with Simplify. Densify adds detail; Simplify removes it. Use densify when you need more vertices, not fewer.