Skip to content

Natural Boundaries

Natural boundaries are lot boundaries defined by a natural feature such as a creek, river, or lake shore. On a survey plan, the natural boundary is shown as a curved line (the irregular boundary) with short traverse lines along the bank used for lot closure.

R3Survey supports natural boundary export for common scenarios — a single bank of a creek or river forming part of a lot boundary.

How it works

In the NSW LandXML format, a natural boundary is represented by:

  1. An IrregularLine element — the curved shape of the natural boundary for visualisation (from a spline)
  2. Traverse observations — short straight-line segments between points along the bank, used for lot closure and area calculation

R3Survey generates both of these automatically from your drawing.

Drawing a natural boundary

Step 1 — Draw the lot boundary polyline

Draw the lot as a closed polyline on the Boundaries layer as normal. Where the lot follows a natural boundary (e.g. along a creek), draw short straight-line segments along the bank — these are the traverse points used for lot closure.

Tip

The short segments along the bank don't need to follow the exact curve — they are the traverse between surveyed points along the natural boundary. The spline (Step 2) provides the smooth curve for visualisation.

Step 2 — Draw a spline along the natural boundary

Draw an AutoCAD spline (SPLINE command) along the natural boundary. The spline represents the actual shape of the creek/river bank.

The spline must:

  • Start and end at the same points as the natural boundary run on the polyline (the corners where the boundary transitions from straight lines to the natural boundary)
  • Pass through or near the traverse points along the bank

The exporter matches the spline to the natural boundary run by checking that the spline endpoints coincide with the polyline corners.

Step 3 — Set the boundary type to Natural Boundary

Select the lot polyline and open the Survey Leg Properties expander in R3PROPERTIES. For each segment that follows the natural boundary:

  1. Use the Current Leg selector to navigate to the segment
  2. Set Boundary to Natural Boundary

Leave all straight-line segments (the non-natural parts of the lot boundary) as Linear Boundary.

Step 4 — Dimension the plan

Run R3DIMS as normal. Natural boundary segments are routed to the Natural Boundary Line Table (R3_NATBDY_LINE_TABLE) rather than the standard short lines table. Insert this table in the drawing using R3INSERTTABLES before running R3DIMS.

The natural boundary segments appear in the table with sequential numbers, showing bearing and distance for each short traverse line along the bank.

Step 5 — Export

Run R3EXPORTLANDXMLNSW. The exporter automatically:

  1. Detects consecutive segments marked as Natural Boundary
  2. Finds the matching spline (by endpoint coincidence)
  3. Replaces the traverse segments with a single IrregularLine element using the spline geometry
  4. Generates traverse observations between the fit points along the spline for lot closure
  5. Tags the intermediate points as natural boundary points

Area calculation

Area is calculated to the right-line boundary (traverse), not the spline curve

R3Survey calculates areas from the polyline vertices (the short traverse lines along the bank), not from the spline curve. This is correct per the Registrar General's Directions, which specify that areas should be calculated to the right-line boundary.

However, you should be aware that the area shown in R3LOTEDIT and the exported area are based on the traverse points, not the smooth curve. If the traverse points are widely spaced, the right-line area may differ noticeably from the true area along the natural boundary. Use closer traverse points for better accuracy.

You may need to enter an area override if the calculated traverse area is not appropriate for the plan.

Limitations

  • Single bank only — only one bank of a creek/river is supported. Plans showing both banks or using the centreline as the boundary are not yet supported.
  • Current position of waterline — tidal boundaries are not yet supported.
  • Compiled irregular boundaries — compiled plans with irregular boundaries (no traverse) are not yet supported.
  • Concurrent irregular lines — two lots sharing the same natural boundary (e.g. a creek between two lots) are not yet supported.

See also