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Dimmed Aerial

April 18 2011 | 4 comments
Categories: Symbology

I have high quality color aerial photography. I'm trying to reproduce the look of the FEMA DFIRM panels and "gray out" or dim or "blue out" the aerials.

Thanks.

Mapping Center Answer:

I am assuming that what you are referring to is in the examples on this web site: http://www.fema.gov/library/viewRecord.do?id=2996. If not, please send us another question here on Ask a Cartographer to let us know which maps you want to replicate either by sending a URL to the web site with the maps or by adding an example map as an attachment. If the maps are like those on the web site I noted, read on!

For the map with the two brown tints, you can simply add a polygon fill to those two areas using brown colors that are slightly darker than what you would finally like to see on the map. Then use the Transparency option (on the Display tab of the layer properties dialog) to set the transparency of the polygons.

For the maps with the blue pattern fills, you can use a similar approach but instead of using a simple fill symbol, you would use a marker fill symbol (to fill the polygon with dots) and/or a line fill symbol (to fill the polygon with lines). You can use these together by simply duplicating the layer in the Table of Contents and drawing the marker fill symbol layer over the line fill symbol layer (be sure to use no outline on the bottom layer so that you do not duplicate the border).

Dimmed Aerial posted by Richard White on May 5 2011 11:48AM
Actually, I'm trying to mute out the aerial, not reproduce the polygon fill. I have a very high resolution, color image and I want to mute out the colors.
Effects toolbar - Dimming option posted by Aileen Buckley on May 5 2011 12:05PM
You can adjust the brightness, contrast, and transparency of the image using the Effects toolbar options. To add this toolbar, click Customize on the top bar menu, then click Toolbars, and click Effects. If you put the image into as basemap layer, you can also use the Adjust Dim Level option on this toolbar.

Here is an online help topic on the Effects toolbar:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00s50000001m000000.htm

Here is an online help topic on basemap layers and the Dimming option:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00s500000017000000.htm
Basemap did the trick for color posted by Richard White on May 5 2011 1:16PM
Thanks -- the dim worked perfectly.

I'm still not seeing a symbology option for displaying a three-band color image as gray scale. I can create a layer for each band, gray scale, set there transparency, and stack them in the correct order. Then dim the collection.
Multiband to grayscale posted by Rajinder Nagi on May 6 2011 2:19PM
You can do this through the Image Analysis Window (http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Image_Analysis_window_Processing_section/009t000000m7000000/). Open the Image Analysis window by clicking Windows on top bar menu and then clicking Image Analysis. Now in Image Analysis window click the color aerial imagery and under the processing section of the Image Analysis window, click Clip. This will generate a new temporary layer and add it to the Table of Contents. Now right click the layer and click Properties. In the Layer Properties window click the Functions tab, right click the Clip function, and insert the grayscale function instead: (http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009t0000004w000000.htm). This will open a dialog box in which you can give different weights to each band. The results will be a one band image, which is temporary. You can make this permanent by right clicking the layer and then clicking Data then Export Data. You will then need to provide location, name and format of the permanent file.
Hope this helps!

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