Troubleshooting -9999 Elevation (Z) Values in LP360 Features

📌 Problem

In LP360, feature vertices with a Z value of -9999 indicate that the software was unable to resolve a valid surface elevation at that vertex location at the time the feature was created or modified using the Feature Edit tools. This most commonly occurs during Auto-Z or feature conflation workflows and does not indicate corrupted data.

🧠What Does -9999 Mean?

• -9999 represents a no-data elevation value.
• It is assigned when a feature vertex falls at a location where no valid surface Z can be computed.
• The vertex is retained so that horizontal (XY) geometry and vertex spacing are preserved.

🧠Is This a Data Error?

Not typically. Vertices with -9999 elevations indicate a surface sampling limitation rather than invalid LAS data or feature corruption.

🔍 Common Scenarios Where -9999 Occurs

1. Surface Has Local Gaps or Edge Voids

Small holes, thin triangles, or boundary conditions in the active TIN can prevent elevation resolution. This most commonly occurs along pavement edges, clipped datasets, or LAS boundaries.

What to check:

• Enable TIN display and inspect the surface locally.
• Review the profile view at the affected vertex locations.

2. Feature Geometry Falls Outside Actual LAS Coverage

Vertices may lie slightly beyond the LAS boundary due to snapping, offsets, or aggressive vertex spacing.

What to check:

• Zoom in and verify that vertices fall within valid LAS extents.
• Confirm no clipping boundaries are excluding nearby points.

3. Active Surface or Filter Is Too Restrictive

Using ground-only or otherwise restricted point filters can expose small surface gaps that do not exist in denser point sets.

What to check:

• Confirm which surface or filter Auto-Z is using (e.g. Ground vs All Points).
• Temporarily test with a less restrictive filter to compare results.

4. Auto-Z Vertex Spacing Is Very Tight

Creating vertices at very short intervals (for example, every 1–2 map units) increases the likelihood of sampling unsupported surface locations.

What to check:

• Slightly increase vertex spacing and retry feature creation.
• Compare results using different Auto-Z spacing values.

Why -9999 Vertices Disappear When Using Respace or Pure Drape

When using Respace or Pure Drape:

• Only vertices that can be assigned a valid Z are retained.
• Vertices that cannot resolve a surface elevation are omitted entirely.

This results in cleaner elevation values, but may reduce vertex density compared to Auto-Z drape modes that preserve spacing.

✅Recommended Approaches

📚 Related Articles

• Auto-Z Modes
• Feature Conflation
• Respace Geometry
• Surface and Filter Management
• TIN Inspection and Profile View

📬 Need Help?

If you're still stuck, please Contact Support for assistance.