Creating a polygon grid with specified coordinates (Maritime Charting)

Polygon grids are grids that are created over a specified extent and stored in a polygon feature class. The grid divides the specified extent into cells so that you can systematically review a large dataset. In the polygon grid, individual grid cells are polygon features that can be attributed and selected. This type of grid can be used with applications such as Data Reviewer to divide large extents into more manageable sections.

These grids can be used during Reviewer sessions to manage both visual and automated quality control. With Reviewer, the polygon grid can be associated with the Reviewer table and the grid information associated with individual records. Cells that contain features that have been recorded as records in the Reviewer table have the QC_GRID field populated with polygon grid information.

Before creating the polygon grid, ensure that the data you use meets the following conditions:

• It is stored in a geodatabase that has been created in ArcGIS version 9.3 or higher.
• The X, Y tolerance for the grid must be larger than the geodatabase precision.

Note:

If the datum does not match, a transformation is applied to the grid extent.

Defining the polygon grid workspace

The workspace is the location where the polygon grid is created. The polygon grid can be created in any type of geodatabase and can be at the root level of the geodatabase or in a feature dataset.

Steps:

1. Start ArcMap.
2. On the Data Reviewer toolbar, click Data Reviewer > Create Polygon Grid Wizard.

   The Create Polygon Grid Wizard - 1 dialog box appears.

3. Click Browse.

   The Select Workspace or Feature Dataset dialog box appears.

4. Navigate to the geodatabase or feature dataset in which to store the grid.
5. Click Select.

   The Create Polygon Grid Wizard - 1 dialog box appears.

6. Type a name for the grid's feature class in the Feature Class text box.
7. Click Next.

   The Create Polygon Grid Wizard - 2 dialog box appears.

Specifying the grid extent

The grid extent is the area that the polygon grid covers in the map. With the Create Polygon Grid Wizard, you have several options for specifying the extent of your grid. They range from manually defining the extent with a bounding box to using coordinates to define the grid extent.

You can define the grid extent using specific coordinates. This allows you to create the extent of the grid based on a specification document that may have coordinates that define the boundary of the grid. A minimum of three coordinates can be used to determine the extent of the grid.

The coordinates can be defined in decimal degrees or degrees, minute, and seconds. You can also change the order of the y- and x-values.

Steps:

1. On the Create Polygon Grid Wizard - 2 dialog box, choose the Define Using Coordinates option.
2. Click Define Extent.

   The Input Coordinates dialog box appears.

3. Click the Units drop-down arrow and choose the units to use for your coordinates.
   • DMS xx(x)°xx'xx.xx" (N/S/E/W)—Specify coordinate values in degrees, minutes, and seconds with marks and hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude. This is the default format, for example, 157°31'51.96"W, 21°06'35.28"N.
   • DD xx(x).xx° (N/S/E/W)—Specify coordinate values in decimal degrees with the degree mark and hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude. For example: 157.53°W, 21.11°N.
   • DDDMM.mm N/W—Specify coordinate values in decimal minutes notation with hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude, for example, 15731.87 W, 2106.59 N.
   • DMS (N/W) xxx°xx'xx"—Specify coordinate values in degrees, minutes, and seconds with marks and hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude, for example, (W)157°31'51.96", (N)21°06'35.28".
   • Raw Coordinates—Specify projected coordinate values in a spatial reference that matches the feature dataset you chose in step 3 in the Defining the polygon grid workspace section.
   • Northing/Easting—Specify projected coordinate values in the same units as the spatial reference of the feature dataset you chose in step 3 in the Defining the polygon grid workspace section.
   • DDD.DD N/W—Specify coordinate values in decimal degrees with hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude, for example, 157.53 W, 21.11 N.
   • DM (N/W)xxx°xx.xx'—Specify coordinate values in degrees and minutes prefixed by hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude. This notation uses degree and minute marks, for example, (N)21°06.59', (W)157°31.87'.
   • DD (N/W)xxx.xx°—Specify coordinate values in decimal degrees prefixed by hemisphere characters. Use hemisphere characters N or S for latitude and E or W for longitude. This notation uses the degree mark, for example, (W)157.53°, (N)21.11°.
   • DDDMMSS.ss N/W—Specify coordinate values in degrees, minutes, and seconds followed by a hemisphere character. Use hemisphere characters N or S for latitude and E or W for longitude, for example, 1573151.96 W, 210635.28 N.
   Tip:

   You can customize coordinate display order and precision in the Coordinate Display pane on the Production Properties dialog box.

4. Type the y-coordinate in the Y (Latitude) column.
5. Type the x-coordinate in the X (Longitude) column.
6. Repeat steps 4 through 5 to define at least two more coordinates.
   Note:

   A minimum of three coordinates must be defined for an extent.

7. Click OK.
8. Click Next.

   The Create Polygon Grid Wizard - 3 dialog box appears.

Defining the grid layout

The grid layout determines the number of rows and columns the polygon grid is going to have. You can define the layout according to a specific number of rows and columns, or you can use the coordinate system to determine the intervals at which rows and columns are created.

Steps:

1. On the Create Polygon Grid Wizard - 3 dialog box, choose an option for setting up the grid layout.
   • Rows and Columns—You define the grid layout by designating a number of rows and columns.
   • Coordinate System—You define the grid layout based on a coordinate system, the starting x- and y-coordinates, and the interval at which you want the cells to be created.
2. Define the layout for the polygon grid.

   To define the grid layout using rows and columns	Choose the Rows and Columns option, then type the number of rows you want in the Rows text box and the number of columns you want in the Columns text box. The default value for both is 10.
   To define the grid layout using the coordinate system	Choose the Coordinate System option, then click Coordinate System to choose the coordinate system you want to use to define the grid layout. Type the starting point in the X Start and Y Start text boxes, click the drop-down arrows to define the units of measurement, then type the interval for the cells in the X Interval and Y interval text boxes.

3. Click Finish.

   The polygon grid is created in the specified dataset or workspace and added to the map.