Solutions for topology errors

When you use the S-58 Error Manager tool to validate products in a maritime database, results are reported and grouped according to severity and type of error. Some of those errors can be topology-related and could impact multiple maritime features. There are several ways to correct topology errors. Different error types have different solutions available for them. The following error types and their solutions are presented here:

  • Floating DEPCNT features
  • Overlapping polygons
  • Rule violations for Must Be Covered By
  • Self-overlapping features
  • Vertices snapping to the S-57 precision

Floating DEPCNT features

The following image shows error 43—DEPCNT does not coincide with two Group 1 objects or is not within an UNSARE or DRGARE.

Error 43 message in the S-58 Error Manager

This warning may be returned when a DEPARE feature is not generated due to a floating DEPCNT feature, or when a gap between the DEPCNT feature and the SOE boundary exists.

A gap between the DEPCNT feature edge and SOE boundary

This issue can be fixed by extending the DEPCNT feature to eliminate the gap and splitting the DEPARE feature with the extended DEPCNT feature. To extend the DEPCNT feature, you can use tools from the Modify pane, such as Edit Vertices Stützpunkte bearbeiten or Extend or Trim Verlängern oder kürzen.

DepthsA feature extended with the Extend or Trim tool

Using the Edit Vertices tool Stützpunkte bearbeiten, remove the original end vertex after extending the DEPCNT feature.

DepthsL vertex selected with the Edit Vertices tool

Once the DEPCNT feature is extended to snap to the boundary of the SOE, the DEPARE feature can be split using the Split tool Teilen from the Modify Features pane. The mandatory S-57 attributes must be verified, and if necessary, updated on the newly created DEPARE feature.

Split tool applied to a DepthsA feature

Overlaps

The following image shows S-58 error 42—Group 1 coverage is not correct, a hole or an overlap exists, where both DEPARE as well as DEPCNT features are flagged due to an overlap of a DEPARE polygon feature.

Error 42 coverage is not correct message in S-58 Error Manager

Errors caused by overlapping polygons can be realigned, merged into one of the polygons, subtracted from both, and turned into a separate new polygon feature. The Align Edge tool Ausrichten der Kante can be used to reshape the overlapping DEPARE topology edge to match and be coincident with the neighboring DEPARE topology edge, as shown in the following image:

Reshaped overlapping DEPARE topology edge

Must Be Covered By

The following image shows S-58 errors 42—Group 1 coverage is not correct, a hole or an overlap exists and 519a Skin of the earth (Group 1) objects do not cover the data coverage (M_COVR=1), where a DEPARE feature is missing and therefore not covering the M_COVR polygon feature.

Error 42 Group 1 coverage is not correct message in S-58 Error Manager

Errors caused by rule violations for Must Be Covered By can be fixed by creating a feature. You can specify a new DEPARE feature from the Create Features pane and use the Trace tool Verfolgung to create a feature, as shown in the following image:

A feature created with the Trace tool

Must Not Self Overlap

The following image shows error 40—Linear objects with the same class, attribute values which are connected and are not chained together, in which a FERYRT feature is self-overlapping.

Error 40 message in S-58 Error Manager

Errors caused by a self-overlapping feature can be fixed by deleting the extraneous vertex through the Edit Vertices tool Stützpunkte bearbeiten.

Editing tools

This can also be accomplished in other ways, including editing in the Modify Features pane or manually removing through the context menu.

The following image shows editing in the Modify Features pane:

Modify Features pane

The following image shows manually removing the extraneous vertex through the context menu:

Extraneous vertex removed

Vertices snapping to the S-57 precision

When exporting to S-57, the coordinates of the vertices are rounded to the S-57 precision. In some cases, vertices that are nearly within the S-57 tolerance in the database will fall within the tolerance after being rounded. This may result in vertices being snapped on export, causing various S-58 errors. The examples below demonstrate how to solve this issue using topology editing tools.

Partially duplicated edges

The following image shows S-58 error 1—Partially duplicated edges. This error is returned due to a DEPCNT vertex near an edge of M_COVR that gets snapped during the export.

Partially duplicated edges error in S-58 Error Manager

To investigate the issue, use the Edit Vertices tool Stützpunkte bearbeiten with the features participating in the edge to see which vertices may snap when exporting.

Edit Vertices tool used to select a snapped vertex on DepthsL feature

To solve this issue, remove or move the vertex slightly away from the edge using Select edge or node Topologie auswählen on the Edges editing tab of the Edit Vertices tool Stützpunkte bearbeiten.

Learn more about editing topological vertices

Vertex selected with Edit Vertices tool

Boundary crosses itself

The following image shows S-58 error 78—The boundary of an area object crosses itself.

Error 78 message in S-58 Error Manager

This error is returned because the area of the DEPARE object is crossing itself. The issue is introduced when the coordinates of a vertex are rounded to the S-57 precision and the vertex is relocated in the exported product.

Example of a vertex relocated

Depending on the scale of the product, the issue can be solved by either removing the cutback part of the DEPCNT and DEPARE features or slightly moving the vertex that gets relocated in the exported product.

If removing the cutback part is preferred, the Reshape tool Umformen can be used to reshape feature geometry. The cutback is removed by drawing a linear shape across an edge as shown in the image below.

Example of a cutback removed using the Reshape tool

Hinweis:

When reshaping a feature, the original feature attributes are preserved. To completely replace feature geometry, use the Replace Geometry tool.

Alternatively, the vertex that gets relocated can be slightly moved using Select edge or node Topologie auswählen on the Edges editing tab of the Edit Vertices tool Stützpunkte bearbeiten.

Example of a vertex moved with the Edit Vertices tool