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Management Requirement Shapes and Vertex Limits
There are no formal data standards for Management Requirement (MR) shapes. Each shapefile uploaded represents the spatial area for a single Management Requirement. MR shapes must be polygons. To represent a Management Requirement as a line or point, you need to buffer them into a polygon before attempting to use them as an MR shape.
If the incoming shapefile has multiple records, WFDSS dissolves them into a single polygon. Attributes in the shapefile are ignored. The Management Requirement’s label and description are entered into the WFDSS Data Management/Unit Shapes tab when the Management Requirement shapefile is uploaded. To load multiple Management Requirements, you must load them one shapefile at a time.
There is a 150,000-vertex limit for MR shapes. It is important to consider that for shapes that extend beyond the unit boundary. By default, WFDSS clips MR shapes to unit boundaries. This step ensures that you do not have any Management Requirements that apply outside your area. This can result in a fairly simple MR shape gaining significant complexity if the unit boundary is complex in the area where the clip occurred. For example, a shape with 129K vertices could bounce back with a message telling you that there were 150K vertices. Pay attention to the error messages you get if an MR shape fails to load. It often mentions that a clip occurred and there was a violation of the vertex limit.
Here are some tips for dealing with complex MR shapes:
- You can count the vertices in your MR shape in ArcGIS by adding a Double field called "VertCnt" and calculating its value with the FieldCalculator Python expression: Unable to render embedded object: File (shape) not found..pointcount. Make sure the Python Parser radio button is selected. If a shape exceeds the vertex limit, try one or more of the following:
- Ensure the shape is already in the NAD83 Geographic coordinate system (GCS_North_American_1983), otherwise WFDSS reprojects it which may add vertices.
- Ensure the shape is a multipart polygon (one table record) instead of a singlepart polygon (multiple table records). Use the Dissolve tool to accomplish this.
- Clip the shape to your FMU/SO boundaries prior to uploading, otherwise WFDSS may add vertices.
- Use the Simplify Polygon tool to reduce extraneous vertices while preserving the polygon shape.
- Run the Repair Geometry tool on the shape before uploading to WFDSS to get rid of invalid geometries.
If a shape is still over the vertex limit, run the Buffer tool on the shape using a small negative buffer value (e.g., -2 meters). This may reduce the likelihood that WFDSS shape processing will lead to an increased number of vertices. Clip and Run Repair Geometry again for good measure.
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