Geospatial · Build and fix geometry

Poly Build

Connects ordered points into a line or polygon, or wraps them in a hull or bounding box, optionally one shape per group. For example, GPS points into route lines.

Also known as: Points to line, convex hull

How it works

Group by makes one shape per distinct value; empty collapses the whole input into one feature. Pick the Point geometry column. Output type is Line, Polygon (closed), Convex hull, Bounding box or Concave hull. Line and Polygon connect the points in the Order by column's order, or sorted by the point geometry itself when it is empty, so set it whenever the order matters, and Polygon closes the ring by repeating the first point. The hulls and the box take the group's points as a set. Concave hull has a Detail between 0 and 1, 0.5 by default, where lower hugs the points more tightly. For lines, Extend by prolongs the line past its ends in the units of the coordinate system (degrees on lon/lat; Reproject first for metres), at Both ends, Start only or End only. The shape lands in Output column, geom by default.

Inputs and outputs

Settings

{
  geometryColumn: string
  groupByColumn: string (optional)
  sequenceColumn: string (optional)
  outputType: "line"|"polygon"|"convex-hull"|"bbox"|"concave-hull"
  concaveRatio: number (0-1, concave-hull only)
  extendBy: number (line only, 0 = off)
  extendEnds: "both"|"start"|"end"
  outputColumn: string
}

Example

GPS fixes into one route per vehicle: point geometry column geom, group by vehicle_id, order by fix_time, output type Line.

More in Build and fix geometry

• Make Point — Turns longitude and latitude columns into points you can map and use in other spatial nodes.
• Make Valid — Repairs broken shapes, such as self-crossing polygons, so later spatial steps don't fail on them.
• Reproject — Converts geometry from one coordinate system to another. Use it before measuring or overlaying layers that come in different projections.
• Poly Split — Breaks multi-part shapes into single parts, one row per part, such as the islands of a country.
• Remove Holes — Fills in the holes inside polygons, keeping only the outer boundary.
• Dissolve — Merges shapes into one, or one per group, so the inner borders disappear. For example, county outlines into one outline per state. To keep totals alongside the shapes, use Aggregate's Union (dissolve).