topic Reverse engineering an existing map from .emf to Arcmap in Geoprocessing Questions

Reverse engineering an existing map from .emf to Arcmap

LiamHennessey — Wed, 04 Jul 2012 14:44:06 GMT

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

Re: Reverse engineering an existing map from .emf to Arcmap

DarrenWiens2 — Wed, 04 Jul 2012 15:54:26 GMT

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.

Re: Reverse engineering an existing map from .emf to Arcmap

LiamHennessey — Thu, 05 Jul 2012 13:25:52 GMT

Thanks, that sounds promising. I will let you know how I get on.

Re: Reverse engineering an existing map from .emf to Arcmap

LiamHennessey — Fri, 06 Jul 2012 15:22:19 GMT

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.'

Re: Reverse engineering an existing map from .emf to Arcmap

DarrenWiens2 — Tue, 10 Jul 2012 14:33:07 GMT

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.