A gradient map displays a range of colors based on information from points, polylines, and polygons. The centroid of an polygon, all vertices of a polyline, and center of a point are used as data point locations and the data value of the polygon, polyline, or point is interpolated onto a grid. The gridded data values are assigned colors based on the selected color spectrum. The resulting map is a smooth color spectrum between the original data.
For polygons, the data originates at the polygon's centroid (geographic center). The color spectrum blends across area boundaries. If you would rather have a discrete colors for each area, use the hatch map instead.
For polylines, the data originate at all vertices on the polyline. The color gradient is drawn in a rectangular shape that encompasses all the polylines.
For points, the data originate directly on top of the points. The color gradient is drawn in a rectangular shape that encompasses all the points.
Click the Map | Create Map | Gradient command to create a gradient map. Edit gradient map properties in the Property Manager.
See Creating and Editing Thematic Maps for information on creating a map, changing a map to another map type, and changing map properties.
The Property Manager for a gradient map has General, Gridding, Data Labels, Info, and Map pages. Click the preceding hyperlinks for information on properties in each of the property manager pages.
The Map page in the Property Manager for a gradient map controls the color mapping method, data limits for colors, color spectrum, and boundary options.
Edit gradient map properties in the Map page of the Property Manager.
Color and data options for the gradient map are in the Gradient section of the Map page. Select Worksheet data limits, Grid Z limits, or User defined from the Color mapping method list. Selecting Worksheet data limits sets the Minimum data for colors and Maximum data for colors fields to the minimum and maximum data values in the linked worksheet. The Grid Z limits method sets the Minimum data for colors and Maximum data for colors to the minimum and maximum grid limits.
Type a value into the Minimum data for colors or Maximum data for colors to set user defined color limits. Adjusting the data limits automatically changes the Color mapping method to User defined.
The Colors property sets the color spectrum used in the gradient map. Click the current color spectrum to select a preset color spectrum. Click the button to create a color spectrum in the Colormap dialog.
Select a color for blank nodes and nodes outside the Minimum data for colors and Maximum data for colors range in the Blank node color list. Click the current color to select a color from the color palette. Click the button to select a color or create a custom color in the Colors dialog.
The Boundaries group on the Map page contains options for gradient map boundaries. Click the Keep layer polygon fills check box to show fills from polygons on the gradient map layer on top of the gradient map fill.
Click the Limit map to boundaries check box to limit the gradient map fill to the boundaries on all layers. When Limit map to boundaries is not checked, the gradient map fills the bounding box for the objects on all layers.