Masking

Masks are used to hide features, or sections of features, so that other features can be displayed without overlap. A common example of masking is creating a gap in a depth contour so that the contour value may be legible. In almost all cases, masks are created by taking a polygon feature and creating a relationship between the polygon and the feature it is masking. Steps on how to perform the two types of masking, Feature Outline Masks and Representation Masks, are outlined below.

Creating and symbolizing intersecting layer mask features

Creating intersecting layer mask features

The Intersecting Layers Masks geoprocessing tool creates masking polygons at a specified shape and size at the intersections of symbolized input layers. For nautical charting purposes, this tool can be used to create masks in locations where certain features, like regulated areas or danger areas, intersect the coastline.

Steps:

1. In the ArcToolbox window, click the plus sign (+) next to the Nautical Tools toolbox, click the plus sign (+) next to the Cartography toolset, then double-click the Intersecting Layers Masks geoprocessing tool.

   The Intersecting Layers Masks dialog box opens.

2. Click the Masking Layer drop-down arrow and choose the layer from which you want to create masks.
3. Click the Masked Layer drop-down arrow and choose the layer you want to mask.
4. Click the Browse button next to the Output Feature Class parameter and browse to the feature class that will contain the mask features.
5. Leave the defaults for the Reference Scale and Calculation coordinate system parameters.
   Note:

   It is important that you work in a map document where the projection and reference scale are defined. Define them now if necessary and return this step.

6. Type the appropriate size for the mask in the Margins text box so that when it's generated, it completely covers the symbol levels that you want to mask.
7. Leave the defaults for the Mask Kind, Create masks for unplaced annotation, and Transfer Attributes (optional) parameters.
8. Click OK.

   The tool runs, and the mask polygons are added to the map document's Table of Contents.

Symbolizing the mask features

You can now set the symbology for the new generated polygon layers so that they can mask the features that are coincident with the coastline so that the coastline takes precedence.

Steps:

1. Right-click the new mask polygon layer and click Properties.

   The Layer Properties dialog box appears.

2. If necessary, click the Symbology tab.
3. Choose Features from the Show list and click the symbol.

   The Symbol Selector dialog box appears.

4. Choose No Color for both the Fill Color and Outline Color options.
5. Click OK to close the Symbol Selector dialog box.
6. Click OK to close the Layer Properties dialog box.
7. Repeat for each mask layer that has been added to the Table Of Contents window.

Setting the Advanced Draw Options

You can now set the mask properties in the Advanced Draw Options dialog box to set the polygon mask layers and the layers that are being masked.

Steps:

1. Right-click the data frame in the Table Of Contents window and click Advanced Drawing Options.

   The Advanced Drawing Options dialog box appears.

2. Check the Draw using masking options specified below check box.
3. Check the Enable to associate levels to masked layers check box.
4. From the Masking Layers list, choose the newly created mask polygons.

   This defines the new polygons as the layers that will be used as the masks.

5. From the Masked Layers list, check the check boxes next to the layers you want to mask.

   This defines the layer to be masked. Each mask layer will directly correlate to the layer it is masking. For example, the RestrictedAreasAndLimitsA_CLMasks layer will mask the RestrictedAreasAndLimitsA layer where it is coincident with the coastline.

6. Click OK when you are finished.

Creating Feature Outline Masks

Feature Outline Masks are used for masking conflicts between geographic features (usually linear features) and annotation, such as with depth contours and depth contour annotation. By using Feature Outline Masking, text is made more visible without compromising the integrity of the data. It is also beneficial in dealing with large datasets because it works on an entire feature class at once. However, a selection set may be entered if you do not want to run the tool on the entire feature layer. In the following steps, depth contours (the DepthsL feature layer) is the example used.

Steps:

1. Start ArcMap.
2. Open the product map document.
3. Click the ArcToolbox Window button on the Standard toolbar.

   The ArcToolbox window appears.

4. In the ArcToolbox window, click the plus sign (+) next to the Nautical Tools toolbox, click the plus sign (+) next to the Cartography toolset, then double-click the Feature Outline Masks geoprocessing tool.

   The Feature Outline Masks dialog box appears.
5. For the Input Layer parameter, click the drop-down arrow and choose DepthsL Anno (or NaturalFeaturesL Anno, and so on).
6. For the Output Feature Class parameter, browse to your database > Masks feature dataset and give your output feature class a logical name, such as DepthsLAnno_Mask.
7. For the Reference Scale parameter, enter the reference scale of your chart.
8. For the Calculation coordinate system parameter, choose your chart's coordinate system.
   Note:

   If you have already set the reference scale and the projection for your chart during previous steps, the Reference Scale and Calculation coordinate system parameters should automatically populate for you.

9. For the Margin parameter, leave the unit in points and set it to a low number, such as 2 or 3 (rerun the tool to make this larger or smaller if necessary).

   If your agency has a set standard, change the units and value accordingly.

10. For the Mask Kind parameter, leave as the default CONVEX_HULL.

    However, there is the option of choosing other shapes.

11. For the Create masks for unplaced annotation parameter, click the drop-down arrow and choose ONLY_PLACED.
12. For the Transfer Attributes parameter, use the default value.

    You can transfer attributes such as Feature ID; however, this is not required.

13. Once you have all the parameters set, click OK to run the tool.

    The newly created polygon feature class is added to the Table Of Contents window.

14. Change the symbology of the polygon mask feature classes to No Color and No Outline.
15. In the Table Of Contents window, right-click Layers and click Advanced Drawing Options.

    The Advanced Drawing Options dialog box appears.

16. Check the Draw using masking options specified below check box.
17. In the Masking Layers list, choose DepthsLAnno_Mask.
18. In the Masked Layers list, check the DepthsL check box.
19. Click OK.

    The depth contour sections behind the DepthLAnno_Masks polygons are now hidden.

20. Click the Save Edits button .
21. Repeat steps 2–20 for the Feature Outline Masking of other feature layers as necessary.
22. Create a quality control plot and look for more areas that may need masking.
23. Once identified, repeat the steps above to mask features.
24. Uncheck masking polygons in the Table Of Contents window so that they do not display, or double-check that they have No Color as their fill.
25. Click the Save Edits button .

Creating interactive representation masks

Representation masking allows you to hide any section of a representation rule's symbology. For example, a reef area that borders a coastline delineates its symbol around the entire polygon outline. Since most nautical charts only show the reef symbol along the seaward side of the polygon, the section coincident with the coastline must be masked. In the following steps, reef areas will be used as an example. Representation masking can be used to mask features of any geometry type.

Steps:

1. Open the product map document in ArcMap.
   Note:

   It may be helpful to first identify which feature classes require masking—either on screen or with the aid of a quality control plot.

2. In the Table Of Contents window, right-click the feature class and click Properties to open the Layer Properties dialog box.
3. If necessary, click the Symbology tab.
4. Click the Advanced button on the lower right of the dialog box and click Masking.

   The Masking dialog box appears.

5. Check the check box for the mask feature layer listed to enable representation masking.
6. Click OK on the Masking dialog box to close it.
7. Click OK on the Layer Properties dialog box to close it.
8. Click the Save Edits button .
9. Click the Select tool on the Nautical Editing Cartography toolbar and select the polygon feature you want to mask.
10. Once the polygon is selected, go back to the Nautical Editing Cartography toolbar and click the Mask tool .

    You can adjust the size and shape of the Mask tool cursor by right-clicking the data frame with it and clicking Options.

11. Click and drag the cursor where you want to mask the polygon.
12. To mask line features, repeat the steps above, including the option of adding the line mask feature class (this is also a polygon feature class, although it is used to mask polyline features).

    Steps 13–18 are optional. However, they can help you refine the mask polygons that you create.

13. Click the Add data button on the Standard toolbar.
14. Navigate to your production database, and expand the Masking feature dataset.
15. Choose the Polygon_Mask feature layer and click Add.
16. Click the List By Source button in the Table Of Contents window and change the version of the mask feature layer to match your current edit version.
17. If necessary, change the Polygon_Mask feature class to have an easily recognizable color.
18. If you want to reshape your mask polygon, select it with the Edit tool , then either reshape it with the Reshape tool or move individual vertices.
19. When finished masking, be sure to remove this layer.

    It is important to note that there is also a points masking polygon feature class. However, in most cases, you can simply select individual point representations and mask it by starting an edit session, opening its Representation Properties, then unchecking the box for Visibility.

20. Save the edits by clicking the Save Edits button and the map document by clicking the Save button .

Associating symbol levels with masking layers

Most of the masking done in paper charting can be achieved with simple representation masking, feature outline masks, or intersecting layers masks. Typically, this is sufficient, because the polygons being masked consist of an outline symbol only, with no fill. However, there may be instances where you need to mask only the outline of a polygon feature that contains a fill symbol. To mask specific parts of a symbol, you can use an Advanced Drawing Option feature that allows you to associate specific symbol levels to masking layers. This allows you to pick which parts of the symbol to mask and which to leave unaffected by the mask.

You can use the masking features created during the Creating intersecting layer mask features task to complete the steps below, which will allow you to use symbol level masking.

Activating symbol levels

You must first activate the symbol-level drawing options for the layer, and you must also be aware of which parts, or symbol levels, of the symbol you want to mask.

Steps:

1. Right-click the layer you want to mask and click Properties.

   The Layer Properties dialog box appears.

2. Click the Symbology tab.
3. Click the Advanced button and click Symbol Levels in the list.

   If you're working with a group layer, click Symbol Levels.

   The Symbol Levels dialog box appears.

4. Check the Draw this layer using the symbol levels specified below check box.
5. Click Switch to Advanced View.

   A list of all the symbols appears, as well as their associated numeric symbol-level values. Note the symbol level numbers for the symbol from which you want to mask parts. You will use these later to define which symbol levels will be masked.

6. Click OK on the Symbol Levels dialog box to close it.
7. Click OK on the Layer Properties dialog box to close it.

   You have now activated symbol levels for the feature layer and taken note of which levels within the symbol you want to mask.

Masking symbol levels

You can now set the mask properties in the Advanced Draw Options dialog box to set the polygon mask layers and the layers that are being masked.

Steps:

1. Right-click the data frame in the Table Of Contents window and click Advanced Drawing Options.
2. Check the Draw using masking options specified below check box.
3. Check the Enable to associate levels to masked layers check box.
4. From the Masking Layers list, choose the newly created mask polygon.

   This defines the new polygons as the layer that will be used as the mask.

5. From the Masked Layers list, check the box next to the layer you want to mask.

   This defines the layer to be masked.

6. Click in the Levels column next to the layer you want to mask.

   The Levels text box is activated.

7. Type the values of the levels you want to mask.
   Tip:

   Separate the different levels with a comma.

8. Click OK when you are finished.

   The symbol levels defined in the Advanced Drawing Options dialog box are masked.