Ask A Cartographer

Mirror Data Frames

April 21 2010 | 1 comment
Categories: Page Layout

I'm working on a non-traditional GIS product. I'd like to be able to show two data frames side by side. But, the kicker is, I'd like them to be mirror images of each other. So the left data frame would show correct, and the right data frame would be the reverse.

I think I can achieve this by converting my data frame to graphics, but I'd like them to treat them both like data, instead of graphics.

Thanks, and keep up the great work.

Mapping Center Answer:

It would have to be done through the projection properties if you wanted to keep it "live". And you could only do this for a projection that has a scale factor that you can modify.  What you would do is change the Scale Factor parameter so that it is a negative value.

For example, if your data frame uses a UTM grid coordinate system, the scale factor will default to the correct value of 0.9996.  Change the scale factor to -0.9996 and the map will "flip" and become the mirror image so that things originally on the left are now on the right.

Of course, a "non-live" solution is to convert the layer features to graphics, select all the elements, group them, and flip them horizontally, as you suggested.

Here is another idea...Krovak! posted by Aileen Buckley on Apr 21 2010 3:01PM
OK -- I didn't notice earlier but the solution above will also flip the map top to bottom so it is not JUST a left to right flip. It is both - left to right and top to bottom.

If you want to ONLY flip the map left to right (or top to bottom), then here is an idea: Use one of the Krovak projections (they are actually oblique conic projections!) You will find four of them in the Projected Coordinate Systems > National Grids folder and the names will be "S-JTSK..." (that is the datum that they use). You will first have to change the Latitude of Center and the Longitude of Center to be in your area of interest. Then you will have to change the X Scale to be -1 to flip the map right to left. (To flip it top to bottom, change the Y Scale to -1). Leave the XY Plane of Rotation as it is at zero. You might also have to change the Pseudo Standard Parallel to be in your area of interest, but this is such an obscure and weird projection that I am not really sure what the pseudo standard parallel is and what effect it has on the map. Maybe you can let us know! :-)

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