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.
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.
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 or Extend or Trim .
Using the Edit Vertices tool , remove the original end vertex after extending the DEPCNT feature.
Once the DEPCNT feature is extended to snap to the boundary of the SOE, the DEPARE feature can be split using the Split tool from the Modify Features pane. The mandatory S-57 attributes must be verified, and if necessary, updated on the newly created DEPARE feature.
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.
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 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:
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.
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 to create a feature, as shown in the following image:
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.
Errors caused by a self-overlapping feature can be fixed by deleting the extraneous vertex through the Edit Vertices tool .
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:
The following image shows manually removing the extraneous vertex through the context menu:
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.
To investigate the issue, use the Edit Vertices tool with the features participating in the edge to see which vertices may snap when exporting.
To solve this issue, remove or move the vertex slightly away from the edge using Select edge or node on the Edges editing tab of the Edit Vertices tool .
Boundary crosses itself
The following image shows S-58 error 78—The boundary of an area object crosses itself.
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.
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 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.
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 on the Edges editing tab of the Edit Vertices tool .