7 replies to this topic

[BZero]

Without generalized digitization, what is the best way to extract the colored propagation shown here http://www.antrak.or...a2t/ELM_UHF.jpg That is just an example.

I know you can do it in ENVI and erdas type software, but is there anyway in ArcGIS or FREE software.

Is their a way of delineating the polygons that arise from the Raster to polygon tool in arcGIS? For something like this you would probably get like 1 million polygons which makes it difficult. Unless you resample I guess.

I have a couple other ideas floating around, but nothing definitive that I know would work.

Edited by BZero, 13 November 2009 - 06:43 PM.

[Dustin Edge]

You could try WinTopo. www.wintopo.com
The freeware version has some limitations but I've seen the "choose specific colour" option in it somewhere....

Cheers
Dustin

[BZero]

You could try WinTopo. www.wintopo.com
The freeware version has some limitations but I've seen the "choose specific colour" option in it somewhere....

Cheers
Dustin

I dont think it has that capability. I tried it. Seemed like a decent enough piece of software though.

Although maybe I just missed something

[birdseye]

Is this a project you could do in Photoshop? That would be my first choice, though you risk having to re-georeference it down the road...

Except for retention of geographic information, ENVI would do no better than Photoshop. The problem is the text and road colors interrupting the layers you want. I don't know any non-manual method of removing that stuff. I'd want to go with Photoshop manually because "brushing" over text, roads, etc., goes quickly compared to manual methods of altering polygons.

After all the different colors were touched up to remove text, etc., each on a separate layer, there would be some edges to refine, and then they could be vectorized. If this sample is typical, there would be many polygons but not umpteen thousands. Yes, resampling might be appropriate.

[angel.spatial]

I have heard of some people having luck with ArcScan in ArcGIS, but I think that may be an expensive extension. It's supposed to take rasters and determine vectors based on like values.

http://www.esri.com/...scan/index.html

They offer a 60-day free trial...

I am not sure how much that helps though...

-angel

[frax]

I would do it like this - bring it into photoshop, and make it into an index image. You may need to use the magic wand and selections in doing that, if there are similar tones next to each other, and/or antialiasing. Remove the colors that are used for labels/roads etc. You may want to try to paint these in in Photoshop. Alternatively, you can set these to a new color, and color these later based on their neighbors. Save this out as a TIFF with indexed color.

Next, you need to georeference the image in ArcGIS. In Photoshop, you may have removed all the georeferencing information - what you can do here is to georeference the original image, and then save the points to the new (edited image) and rectify it based on that.

[BZero]

I found that GIMP software is able to do color selection and you can copy and paste that part. Subsequently convert to vector. Thanks for the suggestions though.

[Ted Florence]

Just so you are all aware, opening a raster image and editing it in Photoshop need not necessarily destroy the georeferencing and require re-referencing in ArcMap.
If one has the Geographic Imager plugin for Photoshop ( www.geographicimager.com ) the all referencing will be maintained throughout the Photoshop session and resaved on export.
There are also a number of spatial functions included such as mosaic, tile and reprojection.
Regards
Ted