MAKE POLYGON (MakPol)

Type: Batch Application

Makes closed polygons using existing line segments and centroids.

Detailed Description

Make polygon looks at the spatial relationship of existing line segments and creates enclosing polygons around areas containing centroid symbols. Lines can be collected in any direction, but they must be noded and should not contain any dangling endpoint. Make polygon first looks for all lines in the user specified feature layers, and forms all possible polygon areas from these lines. A polygon is only retained if it has a centroid symbol on the interior. The resulting polygons are placed in a user specified layesr, along with polygons that represent any holes that were found within the main polygons. A drive file is created so the user can examine any centroids that were not enclosed by a polygon, and also any areas that have more than one centroid. Several centroid layers may be searched for at once. Each layer of centroids will have it’s own polygon save layer.

The following assumptions are made about the existing data:

Local Commands

None

Parameters

Workspaces to consider

Determines if entities in All workspaces will be considered, or only those in the current or active workspace.

Processing Area

If ‘All’ is chosen, then the entire file will be processed. If ‘User defined area’ is chosen, only lines that fall completely within a user defined area will be processed. The user area is defined by using the button below this prompt to select an existing closed VrOne line. This is useful for troubleshooting a small area of a file without having to run the full process. By combining this with the Delete target layers option, it is possible to rerun a small area as many times as needed to get the polygons correct (only target layers within the user defined area are deleted).

Id Processing Area

Pressing this button will allow a line to be selected from any currently open VrOne workspace. Once a line has been selected, it will be used if “User Defined Area” is selected for the Processing Area option. The button label will change to indicate whether a user defined area has been selected or not. NOTE: Just selecting a user defined area does not mean it will be used, the Processing Area option must also be set to “User Defined Area”.

2D Feature layers

Layers containing features that do not contain valid elevations on the line points. If creating polygons of all parking lots, then this would contain features such as buildings or sheet cut lines that were not collected with a ground elevation. The points along the resulting polygons that are taken from features in these layers will contain interpolated elevations based on the main search line.

3D Feature layers

Layers containing features that do contain valid elevations on the line points. If creating polygons of all parking lots, then this would contain features such as road edges that were collected with a ground elevation. The points along the resulting polygons that are taken from features in these layers will contain the original elevation value of the feature.

Centroid layers

Layers containing the centroids. This can be any valid layer number line. Any symbol found on these layers will be considered a centroid. The location of centroids that do not fall within a polygon will be written to the error drive file. The location of any duplicate centroids within a single polygon will be written to the error drive file.

Polygon Save layers

The final closed polygons will be placed in this layer. This can be any valid layer number line, but you must have the same number of save layers as centroid layers. Each save layer corresponds to a centroid layer.

Example: Layers "3 4" are specified for the Centroid Layers, and layers "200 201" are specified for the save layers. All polygons associated with centroids on layer 3 will be placed on layer 200, and all polygons associated with centroids on layer 4 will be placed in layer 201. You can also use number ranges. For example: Centroid layers: 3 4 5, and Save layers 200-203.

Hole layers

Polygons that do not contains centroids, and are found inside the main polygons will be stored in this layer in a counter-clockwise direction. This can be any valid layer number line, but you must have the same number hole layers as polygon save layers. Each hole layer corresponds to a save layer.

Example: Layers "200 201" are specified for the save layers, and layers "210 211" are specified for the hole layers. All holes inside polygons on layer 200 will be placed on layer 210, and all holes inside polygons on layer 201 will be placed in layer 211. You can use number ranges.

Work layer

This layer will be used to store temporary lines during the polygon generation process. All existing entities in this layer will be deleted when Make Polygon starts, and the layer will be left empty when Make Polygon has finished.

Maximum point gap

This allows you to specify a tolerance to handle rounding errors between endpoints. Normally, this value can be left at it’s default value (0.0001), but you may need to make it larger if you find that some polygons are not being found because endpoints don’t match up exactly. Don't set this value too high or it can find false point matches.

Delete Target Layers

If set to Yes, then all entities on the Polygon Save Layers, and Hole Layers will be deleted before processing begins.

Identify holes

If set to Yes, then polygon holes will be flagged and placed in the Hole layers. If set to No, then only the main Polygons will be saved to the Polygon save layers. When processing a file for the first time, and you anticipate that there will be some cleanup, you may want to turn this off to save time. After any problem areas have been fixed, you can turn it back on for the final run. On a clean file, this step usually doesn't take too long, but if you have an unclean dataset that is making large polygon regions, a large number of holes may be flagged, leading to a longer run time. If you notice that the Identify holes step (last step in the process) is taking a long time, it may be because large invalid polygon regions are being generated.

Examples

This example shows a typical parking lot area with internal islands and with outside attachments to road edges and buildings.

This is the result of running Make Polygon on the above data.