Reverse engineering an existing map from .emf to Arcmap

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07-04-2012 07:44 AM
LiamHennessey
New Contributor
Hi,
I essentially have flood maps with in a published .emf file available at: http://teigngis.co.uk/About_the_Study.html if you want a look.

I wish to bring these back into Arcmap as the original files are missing. I've converted it to a GIF, then a layer and geo referenced it, but I am struggling with where to go from here. I have two problems:

I wish to clip it, however it is coming up with it not being a feature layer.

I need to also use the legend as a colormap of some sort to convert the data back to being meaningful.


I hope you can help.
Many thanks
Liam Hennessey
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4 Replies
DarrenWiens2
MVP Honored Contributor
1.) With rasters (ie. your georeferenced GIF) you need to use Extract By Mask, not Clip.
2.) You'll have to reclassify your image into meaningful categories. You might want to think about using Maximum Likelihood Classification to group together similarly colored pixels.
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LiamHennessey
New Contributor
Thanks, that sounds promising. I will let you know how I get on.
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LiamHennessey
New Contributor
With the maximum likelihood I need an Input signature file. It may sound silly but can i make one or is there a default one. The error is:

'Input signature file
The input signature file whose class signatures are used by the maximum likelihood classifier.

A .gsg extension is required.'
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DarrenWiens2
MVP Honored Contributor
Read this page about creating signature files. Basically, if you know what classes you want the image to be classified into (ie. the colors on your original map), then draw polygons to use as samples for the classification, and use the Create Signatures tool to make the signature file.
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