Re: How to convert an ArcMap shp. File in an Erdas aoi. File
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Re: How to convert an ArcMap shp. File in an Erdas aoi. File
By Phil J in ERDAS Software Forum
Hi, I'm a new poster...
I've found this very useful for what I'mn doing, thanks.
I wish to make a supervised classification using data I have stored in a shp file. I have converted to aoi using your instructions and now want to import data from the original attribute table to use in the signature editor for the classification. There are around 500 records altogether.
My prolem is that the .aoi appears to be just empty polygons, do you know of a way to import my data for the polygons to be used for the supervised classification?
Many thanks
Phil
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By Cheryl Brantley in ERDAS Software Forum
Hello all,
In 2011 11.0.3 there is a new program that converts shape file to signatures. In the Signature Editor go to Edit, Read Shape file.
Thanks
Cheryl
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Re: How to convert an ArcMap shp. File in an Erdas aoi. File
By Cheryl Brantley in ERDAS Software Forum
All,
I have a document with screen shots on how to move a .aoi to shapefile and vice versa if you want to do a "selected" shapefile to .aoi. Email me at cheryl....@erdas.com and I will be happy to provide that.
Thank you,
Cheryl.
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By Donn Rodekohr in ERDAS Software Forum
Phil,
by "empty polygons" do you mean a polyline that describes a polygon but does not fill? Or do you mean that there are no attributes associated with this polygon?
In the first instance, the solution is rather simple. When displaying the shapefile be sure that the polygon attributes are used so that the polygon is displayed as filled with a solid color. When the selected polygon is displayed it should be a solid yellow polygon. If you are displaying only lines and only the lines are displayed as being selected then the AOI will be an outline, not a polygon.
In the second instance, please realize that an AOI has no attributes other than the geographic vertices. I presume that the 500 records do not represent 500 classes and that one of the attributes in your shapeflie is the land cover class name. You can display the shapefile in a viewer and then open the attribute table. Select all of land cover classes for a single unit, water for example, either manually or by using the Criteria selector. When all of the water polygons show as yellow, copy and paste those into an AOI. Now do a File Save AOI Layer as... function and save the AOI layer as water.aoi. remove the aoi from the viewer. Now do the next land cover class to create a series of land cover AOI files.
In the signature editor you can bring in the AOI files one at a time and use them to create a signature for each land cover class.
There may be a more automated way to do this but this is what I have used in the past and it works. Until AOI's grow selectable attributes or until SigED reads shapefiles directly, I think this is your main alternative.
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By Phil J in ERDAS Software Forum
Thanks for the response, it is indeed the latter situation. I've tried splitting the land classes as you've said but I did this in ARc and created separate shp files for each. Problem is now with the signature editor, I keep getting this message:
Error getting AOI from Viewer.
Use AOI Tools in Viewer to create AOIs for Signature Editor.
I will try what you suggest with regards to creating separate aoi files for each, this sounds like a better way of doing it.
Many thanks,
Phil
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Re: How to convert an ArcMap shp. File in an Erdas aoi. File
By Phil J in ERDAS Software Forum
Cheryl,
I've just noticed your response, that sounds really useful, I'll look into it,
Thanks,
Phil
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By Jarlath O'Neil-Dunne in ERDAS Software Forum
The first part of this video will show you how.
http://letters-sal.blogspot.com/2010/10/clipping-raster-data-in-erdas-imagine.html
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By Phil J in ERDAS Software Forum
Many thanks, everyone. This really helped.
Just another quick one.. I'm trying to create spectral signature files using colour aerial photography as I have previously done using Landsat TM images. However, when I bring in aoi's of different classes into the signature editor for the colour photos, I'm just getting black signatures with no values for any of the three colour bands.
Can anyone think why this may be?
Thanks,
Phil
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By Donn Rodekohr in ERDAS Software Forum
Phil,
This sounds like the images have different projections. AOI's do not reproject on the fly and cannot be reprojected manually. They are pure coordinates only, no projection/Datum/Spheroid information is attached. Therefore, if your aerial photo is in a different projection system than the Landsat data, the AOI will not overlay properly, yielding all blank statistics.
If that is the problem, then reproject the aerial photo to match the coordinate/projection/datum/spheroid of the Landsat data. After reprojection the AOI should overlay correctly and the stats should be non-blank.
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By Phil J in ERDAS Software Forum
Thanks again Donn,
I realised that the reason this was occurring was a result of not creating a mosaic of the many images that I am using. I have now done this and was able to collect signatures using aois that I created using my vector data that I have overlayed on the mosaic.
All seemed to be going well but now having used my .sig file for a supervised classification I am getting many blank values returned in the supervised file attribute table. I'm guessing this is something to do with black areas of no data surrounding my image but can't find a way of getting around this. Nor do I understand why this would be as I only defined 4 classes that I am looking for across the whole image so don't know why any black areas surroung the image would be included. The classes I identified are a rnage of grey appearing pixel clusters.when merged. When I applied the supervised classification the image created appeared completely in these colours.
Many thanks again for your time so far, I'm continuing to look for a solution but if there's anything blindingly obvious that I appear to be doing wrong then please I'd be very grateful if you'd let me know.
Phil