Create a 3-Grid Composite

Use the Grid and Image > Display on Map > 3-Grid Composite menu option (GRIDIMG3 GX) to place an aggregate of three grid images on a map.

This functionality is similar to the ternary image functionality, except that you have a much wider range of colour and grey tables from which to choose. For example, you could use this functionality to display one grid using a colour table, another using a grey table and another using a green table, and create a specialized composite for interpretation and visualization.

3-Grid Composite dialog options

Colouring method

Specify the colour zoning method for rendering colour distributions. Select one of the options below:

  • As last displayed: the grid is displayed in its last viewed state: its previous colour transform is used, and the currently selected colour scheme will be ignored.

  • Default: the default colour distribution method is used.

  • Histogram equalization: your data values are evaluated, and the zones are statistically determined, such that data is equally divided among the histogram bins.
  • Normal distribution: your data is assumed to be normally distributed, and the zones are determined based on the standard distribution for a standard bell curve.
  • Linear: the range of data values are divided linearly into even increments.
  • Log-Linear: the zone values are updated based on the log distribution of the data, and the data is displayed using the log-linear colour distribution.

Script Parameter: GRIDIMG3.ZONE

Grid name 1

Select the first grid name.

Script Parameter: GRIDIMG3.GRID1

Colour table 1

Select the colour scheme for rendering the image of the first grid. If you mouse over the colour scheme entry, a tooltip will display the name of the colour table in its folder. To modify the selection, click on the colour entry and then navigate through the scheme categories.

Script Parameter: GRIDIMG3.COLOR1

Grid name 2

Select the second grid name.

Script Parameter: GRIDIMG3.GRID2

Colour table 2

Select the colour scheme for rendering the image of the second grid. If you mouse over the colour scheme entry, a tooltip will display the name of the colour table in its folder. To modify the selection, click on the colour entry and then navigate through the scheme categories.

Script Parameter: GRIDIMG3.COLOR2

Grid name 3

Select the third grid name.

Script Parameter: GRIDIMG3.GRID3

Colour table 3

Select the colour scheme for rendering the image of the third grid. If you mouse over the colour scheme entry, a tooltip will display the name of the colour table in its folder. To modify the selection, click on the colour entry and then navigate through the scheme categories.

Script Parameter: GRIDIMG3.COLOR3

Render method

Select the render method.

ADD - All the colours are added together.

BLEND – All the colours are added then divided by the number of valid (non-dummy) colours.

BLEND EQUAL – All the colours are added then divided by the number of colours.

Script Parameter: GRIDIMG3.METHOD

Application Notes

Click the New Map button to display a grid on a new map. Click the Current Map button to display the grid on the current map. (For a script file, set 'Script Parameter: GRIDIMG3.NEW' to 1 to create a new map or to 0 to use current map).

A recommended configuration is to use the CYAN.TBL, MAGENTA.TBL and YELLOW.TBL table files.

When using ER Mapper ternary colour images, the band numbers should be specified for each colour grid.

As an example, for an ER Mapper file named "Weshade.ers(ERM)", the following should be entered in the three colour bands:

Red-Cyan grid Weshade.ers(ERM;band=0)

Green-Magenta grid Weshade.ers(ERM;band=1)

Blue-Yellow grid Weshade.ers(ERM;band=2)