Drawing Correct 3D Polylines in Pythagoras

When drawing curved polylines in 3D, every vertex must have a correct height (Z-value). If not, the polyline may snap down to Z=0 at curves. Pythagoras fully supports 3D polylines with height data if you follow the right workflow.

Method A: Draw directly with correct height values

Step 1: Start the polyline tool

• Click Create Polyline in the toolbox on the left.

• At the bottom of your screen you’ll see: Click to define start point of polyline.

Tips for placing points with correct heights

• The cursor snaps to objects and their Z-value if that snap type is active.

• Hold the shortcut key of a snap type to limit snapping (e.g. only to points).

• Check the control panel: if Z = 0.000, you clicked a point without height.

• If no snap is possible and Confirm Operation is active, press Enter and type a Z-value manually.

Step 2: Select the right segment type

Before placing the first point, press the spacebar to toggle between:

• Line segment

• Arc segment

• Curve segment

For curves, use arc or curve segments.

Step 3: Continue drawing segments

• Follow the on-screen prompt at the bottom for the next action.

• Press spacebar again to switch back to a straight segment.

• Always check heights as in Step 1.

• Keep building the polyline with correct Z-values per segment.

Step 4: Finish

Press Enter to validate and close the polyline.

Method B: Draw in 2D and project on a DTM

If you already have a terrain model (DTM):

1. Draw the polyline in 2D.

2. Right-click the line > Edit > Project on DTM.

3. Select the correct DTM.

The polyline is projected onto the terrain and inherits its Z-values. This works only if the DTM is reliable and complete.

Check your result

• Double-click the polyline to open its properties.

• In the Polyline tab you see segment count, slope, length, and type (line/arc).

• View the polyline in 3D mode to confirm it is properly built.

Best practices

• Enable only the snap types you really need.

• Prefer curve segments for smooth bends.

• Use a DTM only if it is accurate and up to date.

Common mistakes to avoid

• Do not use separate arc commands like Draw arc through 3 points. These create only XY data without Z.

• Always verify the polyline in 3D view or with height display.