Create a Three-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

Select the colour method as one of the following options: As last displayed, Default, Histogram equalization, Normal distribution, Linear, Log-linear.

  • The method "As last displayed" will display each grid as it was displayed the last time the grid was viewed, and the colour tables will be ignored.
    If the selected colour scheme is an .itr file or a .zon file, the colours are already attributed to data ranges, and this entry remains disabled.

    • 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)