orthophoto to polygon for wooded area
I'd like to extract a polygon shapefile showing wood/vegetation covered areas starting from a standard raster orthophoto. Please see attached file as an example. Is there a simple method to teach ArcMap 9.2 to do that? Perfect accuracy is not an issue...
Mapping Center Answer:
What you are talking about is extracting wooded land cover from a color air photo. This involves something called image classification, in which you use the colors or tones in the image to identify different features, such as land cover types. Since you are working with a color image, you have more to work with as you can use color as well as lightness and darkness in the image. If the image has multiple bands, that will also help. To help you get started with this process, here are some useful links (note that these are for ArcGIS 10, but the concepts still apply):
- Here is the online help topic for getting started with image classification.
- Here is a blog entry from the Geoprocessing Resource Center that discusses how to classify an image: Raster Image Processing Tips and Tricks -- Part 3: Extracting a Feature from an Image.
- And here is a blog entry on Mapping Center that discusses image classification, albeit with the use of Landsat image services: Classifying Landsat Image Services to Make a Land Cover Map.
In ArcGIS 9.2, things were a little different because the classification tools were located within the Multivariate toolset in the toolbox for Spatial Analyst, instead of on the Image Classification toolbar, as they are with ArcGIS 10. Here is a link to the 9.2 online help to get you started with these tools: An overview of the Multivariate tools. Read this and the related online help topics to step through the procedure with your older version of the software.
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