Creating cartographic data

Many nautical charts show symbols that require you to perform extra processing on the existing S-57 data to get them to display on the chart. The extra processing you perform results in the generation of cartographic features. These cartographic features can then be used to display all the symbols shown on the chart. Two common complex cartographic features are light sectors and Isogonic lines, although there may be several others not described here. Other ArcGIS tools, processes, and workflows may be necessary to prepare the database for chart creation.

Creating light sectors

In S-57 data, light sectors are not captured as series of lines but as a collection of coincident points. These points contain information about the angles and visibility range of the light sectors. The Generate Light Sector tool takes the required information from the points and generates a series of lines that represent light sector limits for chart display. Light sectors may include recommended tracks, obscured sections, and multicolored lights such as WRG (White Red Green). Although any feature class that contains the required information can be used to generate light sectors, light sector limit information is generally contained in the AidsToNavigationP feature class.

Since light sectors are used to display information on a paper chart, it is important that you verify that the chart is properly projected and the reference scale is set. This will ensure that the light sectors display properly on the chart. The reference scale must be set if you want to define the length of your light sectors in page units, as opposed to geographic units. If you completed the Creating borders and grids section, you may have already applied these settings. If working with a Personal/Workgroup ArcSDE SQL Express product geodatabase, ensure that the CartographicFeatures feature dataset is versioned prior to creating light sectors.

Étapes :

1. Open the product map document.
2. To verify that the projection and the reference scale are set, complete the following steps; otherwise, proceed to step 3.
   1. From the main menu, click View > Data Frame Properties.
   2. Click the General tab.
   3. Verify the reference scale or type a value if necessary.
   4. Click the Coordinate System tab.
   5. Verify the projection information or define a projection if necessary.
   6. Click OK to apply changes, or click Cancel to close the dialog box if no changes are necessary.
3. 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 Generate Light Sector geoprocessing tool.

   The Generate Light Sector dialog box appears.

4. For the Input Feature Class or Layer parameter, select AidsToNavigationP or whichever feature class contains the light sector information.
5. If necessary, use the Expression (optional) parameter to create a SQL query to narrow down the number of features.

   For example, you may want to return only red and green lights so that you can generate sectors of a common length from those two colors. Then, you may want to run the Generate Light Sector tool a second time on only the white lights so that you can create longer white light sector limit lines.

6. Type a value in the Boundary Length text box or choose the value from a field.

   If using a field, choose the Field option and select a field such as VALNMR from the drop-down list.

7. Choose the appropriate value from the Boundary Length Unit drop-down list.
8. Type a value for the Sector Arc Radius parameter or select a value from a field.

   If using a field, choose the Field option and select an available field from the drop-down list.

9. Select the appropriate Sector Arc Radius Unit from the drop-down list.

   The Boundary Length and the Arc Length can be real-world measurements, such as Nautical miles, or map units, such as centimeters, provided that your data is projected and the reference scale is set.

10. Leave the Use Light as Angle Origin (optional) check box unchecked.

    This check box allows agencies to make the light the source of origin instead of having seaward as the source of origin, per industry standards. If your production agency uses the sector angles from the light vs. from seaward, then you will need to check this box. Checking this box will flip the sectors. For more information, see Generate Light Sector (Nautical).

11. For the Start Angle parameter, choose SECTR1, or whichever field holds the beginning angle.
12. For the End Angle parameter, choose SECTR2, or whichever field holds the ending angle.
    Remarque :

    In most cases, the start and end angles will be SECTR1 and SECTR2, respectively, with the angle units as decimal degrees. If you are not using S-57 data, select the fields that contain the start and end angles for the light sector limits. Lights that do not have values populated in SECTR1 and/or SECTR2 (or the user-defined fields) are ignored by the tool.

13. For the Output Feature Class or Layer parameter, browse to the CartographicFeatures feature dataset and select the LightSectorsL feature class. Or, you can choose an output location and type a name, and the Generate Light Sector tool will create a new feature class for you.
14. For the Output Symbol Field parameter, do one of the following:
    • Select Symbol from the drop-down list if you are using the LightSectorsL feature class.
    • If you are allowing the tool to create a new feature class for you, type a name for the field that will contain the Symbol value (this value will later be used by VST to differentiate between a light sector limit line and a light sector arc.
15. Click OK to run the Generate Light Sector tool.
16. Repeat as necessary for all navigational aids that have light sectors.
    Remarque :

    If using a versioned environment, you need to reconcile and post to the Default version.

Creating isogonic lines

Isogonic lines are lines joining points on the earth's surface at which the values of magnetic variation are equal. These are also called isogonal lines and isomagnetic lines.

It is helpful to know the magnetic variation of the area in the chart that you are creating. For example, you create sample data points at the four corners of a bounding rectangle, and use the magnetic calculator to calculate magnetic values for those points. The information taken from the sample points can aid you in determining an interval for the isogonic lines. By knowing the general values of your data, you can adequately enter the interval values and have some foresight as to whether your data will straddle a contour with the value you are seeking.

Étapes :

1. Start ArcMap and open your product map document.
2. Ensure that the grid data is still present in the map document.
3. If working in a versioned environment, verify that you are in the appropriate editing version.

   This should also include your input feature class. If using the CLP_Grids FC, be sure that you reconciled and posted back to your DEFAULT version.

4. Ensure that you have the Spatial Analyst extension checked on by clicking Customize > Extensions.
5. Click OK to close the Extensions dialog box.
6. If necessary, set the reference scale.
   1. On the main menu, click View > Data Frame Properties.
   2. Click the General tab.
   3. Set the Reference Scale to that of the panel being created.
7. In the Table Of Contents, expand Grids so that the CLP_Grids layer is visible.
8. In the ArcToolbox window, click the plus sign (+) next to the Nautical Tools toolbox, click the plus sign (+) next to Cartography toolset, then double-click the Magnetic Isolines geoprocessing tool.

   The Magnetic Isolines dialog box opens.

   

9. Choose the CLP_Grids layer from the Input Extent Feature Class or Raster drop-down list (or drag and drop from the Table Of Contents).

   The Input Extent Feature Class or Raster parameter provides the tool with an area (points and lines are allowed as well) via a minimum bounding rectangle from which the isolines will be generated.

10. If you want to narrow down the features of the feature class selected above, then type an expression or click the SQL button next to the Input Extent Selection Set (optional) text box to build an expression for the selection set.

    When you use the CLP_Grids layer, there should be only one feature available, and it most likely will not need a selection set.

11. Input zero for the Altitude parameter, which represents sea level for nautical charts.
12. Leave the Altitude unit parameter as the default set to meters, unless the altitude value was not set at zero.
13. Enter the date in the format of mm/dd/yyyy if you alter it from the current date.

    The Date parameter defaults to the current date; however, this can be changed to go as far back as 1/1/2005 and projected forward as far as 12/31/2014.

14. Change the Output Feature Class parameter by clicking the browse button.
    1. Navigate to your product database.
    2. Open the Nautical feature dataset and click the TidesAndVariationsL layer.

       A yellow warning may appear next to this field, stating that existing values may be overwritten. If you do not want to overwrite existing values, you need to narrow down your input selection with a selection set, or select a new or different layer as the output.

15. For the Output Subtype (optional) parameter, choose MAGVAR_Magnetic Variation from the drop-down list if you are using the TidesandVariationsL layer.
16. For the Output Field (optional) parameter, choose VALMAG from the drop-down list if you are using the TidesandVariationsL layer.
17. Select a field for Magnetic Field Parameter.

    In this example, Declination (Decimal Degrees) is used since most nautical charts show magnetic declination (magnetic variation) as isolines.

    The Raster Cell Size parameter is automatically calculated depending on the selected feature or extent as the Input, and you most likely will not need to change this value.

18. From the Isoline Interval section of the form, choose one of the available methods for determining the intervals of the isolines and fill in value(s) as necessary.

    For the tool to create lines, you must fill out the Base Value (optional) and Interval (optional) or the Isoline Values (optional) in the table.

19. Click OK to run the tool (this may take a few minutes depending on your cell size, interval, and AOI size).

    Several layer files get generated by the tool during processing if the tool is run in ArcMap. They include a temporary polygon feature class for the constant raster, the constant raster (these two are only if a raster was not used as the initial input), a point shapefile (called wmmpoints) created from the raster, and the new or existing feature class containing the generated isolines. These files are stored in C:\Documents and Settings\<user_login>\Local Settings\Temp. If you need to run this tool more than once, it is strongly recommended that you delete all unnecessary files from this location after you have run the tool successfully (or unsuccessfully). By doing so, you will prevent the tool from causing an error when running it again.

20. If using a versioned environment, you need to reconcile your edit version with the DEFAULT version.
21. Save the map document and close ArcMap.
    Conseil :

    The default value for Raster Cell Size has a medium-to-low resolution to cut down on processing time. If you want a higher resolution, which may translate into a longer processing time, multiply the default value by 5. The smaller the cell size, the more detailed the contours, but the longer it takes to process. If the resulting contours are too generalized, the process can be repeated with a smaller cell size.

    Conseil :

    You can choose between selecting the isoline intervals with a base value and an interval at which it will create the isolines, or choose the exact values at which the tool will create the lines. They are both listed as Optional because only one or the other is required, not both. For example, if you do not know what values the tool will create, but want only whole numbers (in decimal degrees for the declination selected above), enter 0 as your base value and 1 as your interval. Keep in mind that large-scale data (less than 100,000) may not span an area with 1 degree of variation. If that is the case, run the tool with a smaller interval (0.001- 0.1) to determine if any usable values are within your area of interest (AOI).

Creating data points for compass roses

Every nautical chart has a compass rose to delineate True North and Magnetic North, as well as assist with angles for orientation, bearing, and traversing routes. In most situations, the compass rose will be represented by the TidesAndVariationsP feature class. However, the representation rule can be applied to any point feature class, as long as it has fields that contain the attributes required to calculate the rotation of the Magnetic North section of the rose. For the compass rose to be portrayed, it needs to be associated with a point feature. In some cases, the TidesAndVariationsP feature class may not contain any features that can be used to display a compass rose on a chart.

The following steps outline how to add a new point feature to the TidesAndVariationsP feature class.

Étapes :

1. Start ArcMap and open the product map document.
2. Identify whether there are any data points in the TidesAndVariationsP feature class.
3. Right-click the feature class and click Open Attribute Table.

   If there are no data points with an FCSubtype value of MAGVAR, continue with this section. If the feature class contains MAGVAR objects, skip this section and move on to Calculating magnetic variation and annual change for compass roses.

4. Add the Production Editing toolbar if necessary by clicking Customize > Production > Toolbar Settings > Nautical Chart Production.
5. Click OK on the ArcMap Settings Change Warning dialog box.
6. Click the Production Start Editing button on the Production Editing toolbar.
   Remarque :

   The Manage Features and Create Attributes, Update Attributes, or Metadata Attributes windows automatically appear when you start an edit session using the Production Start Editing tool.

   Conseil :

   If the Create Attributes, Update Attributes, or Metadata Attributes window does not appear when you start an edit session, click the Show/Hide Attributes button on the Manage Features window.

7. Identify a place on the chart that is not too cluttered to add the rose.
8. Open the Feature Manager window.
   Remarque :

   The Manage Features and Create Attributes, Update Attributes, or Metadata Attributes windows automatically open when you start an edit session using the Production Start Editing tool.

9. In the Manage Features window, scroll to the TidesAndVariationsP layer and click the MAGVAR_MAGNETICVARIATION subtype.

   The Point tool is automatically enabled, and your cursor changes.

10. Click to add a new point. If the exact coordinates of the rose are known, right-click the data frame and select Absolute X,Y, then type the coordinates.
11. If necessary, repeat steps 5–9 to add more compass rose points.
12. Click the Save Edits button on the Production Editing toolbar.
13. Stop editing.

Calculating magnetic variation and annual change for compass roses

The following steps outline how to calculate the magnetic variation and annual change to the appropriate attributes in the Nautical data model.

Étapes :

Ensure that you are not in an edit session.
1. In the ArcToolbox window, click the plus sign (+) next to Nautical Tools toolbox, click the plus sign (+) next to the Cartography toolset, then double-click the Magnetic Calculator geoprocessing tool.

   The Magnetic Calculator dialog box opens.

2. For the Input Feature Class or Raster Dataset parameter, drag and drop TidesAndVariationsP from the Table Of Contents or choose TidesAndVariationsP from the drop-down menu.
3. The Selection Set (optional) parameter is optional for specific features; not entering a selection set means every data point will be calculated.

   You may want to create a Selection Set by building a SQL query.

   An example of a simple query would be FCSubtype = 10 - MAGVAR_MAGNETICVARIATION. This would ensure that only magnetic features are calculated, and other points (such as tidal points) are left out.

4. For the Linear Unit parameter, choose the unit for altitude, such as meters.

   Most nautical charts will have a zero Altitude, so this unit is a necessary but arbitrary parameter.

5. For the Altitude parameter, type a numeric value into the Double field (most likely 0). If using a specific field value, choose the Field option and select a field.
6. Enter the date in the format of mm/dd/yyyy if you alter it from the current date.

   The Date parameter defaults to the current date; however, this can be changed to go as far back as 1/1/2005 and projected forward as far as 12/31/2014.

7. Leave the Output Feature Class (optional) parameter blank, since it's not needed for nautical chart production in most cases.
8. For the Output Declination Field (optional) parameter, choose VALMAG if using ENC data.

   Remarque :

   If your output is the same as your input, or if you already have MAGVAR objects and you are using this tool to recalculate the magnetic variation and annual change because your current features are out of date, the tool will give you a warning stating that the values will be overwritten.

9. Choose VALACM for the Output Annual Drift Field parameter if using ENC data. Again, the tool will warn you that the current values will be overwritten.

   Remarque :

   If using non-ENC data, identify which fields will be calculated, or simply enter the name as a new field.

10. Inputs for parameters in the Additional Fields (optional) area are optional; existing field names or new names may be used for these parameters.

    

11. Click OK to run the tool.
12. Save the map document.