Ask A Cartographer

Mutual legend of two transparent layers

July 30 2007 | 0 comments
Categories: ArcGIS Methods, Cartographic Effects, Page Layout

I am creating a map that uses two raster layers that are transparent. In both raster layers I
am using color ramps (from transparent to yellow, the other from transparent to dark blue).

The map output is great in ArcMap with overlaying both raster layers, just what I am missing is a mutual color ramp legend that goes from yellow to blue.

I have done this with a separate data frame and I have "fooled" the map in placing a non-corresponding legend next to the data frame with the transparency issue. some users just design a separate legend with other non-ESRI graphic software (it is wasting a lot of time).

It is just a work around.

Are there any functionalities in this direction coming in the upcoming releases of ArcGIS?

Mapping Center Answer:

This workaround, as you called it, is actually the accepted method. It sounds like you’ve seen this:

But I thought to include it just in case.

The reason we’ve not created an automated solution is because we’ve been unable to devise a design that handles all cases or one that can even distinguish between the basic kinds of cases. Addressing all the combinations of two, three, or more vector and raster layers overlaying with both feature and layer transparency is effectively infinite. Even for the simple cases where two layers using a small number of classed colors with transparency creates a matrix of possibilities. An elevation raster over a hillshade raster creates a huge matrix of possibilities that are effectively meaningless in matrix form anyway. Map readers typically expect some sort of “representative sample” from the map to be annotated with the meanings in an orderly fashion.

[the original response then contained a draft of this Mapping Center blog posting on Creating a Legend for Hypsometrically Shaded Relief.]

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