Converting raster data into GIS objects using ArcScan

 

ArcScan is an extension that can be installed with ArcDesktop. It contains the tools that allow for creating features from scanned images, such as plat maps. To check whether ArcScan is installed, open ArcMap, go to Tools > Extensions, and see whether ArcScan is available. If it is, make sure it is checked to enable it. If not, run the ArcDesktop install again, and choose a custom or complete install to add the ArcScan extension.

In ArcMap, you'll need to load the raster data into a new or existing map. To do so, click the Add Data button and find your image file. This will add the image as a new raster layer. If ArcMap asks you to create Pyramids, select yes.

The raster needs to be symbolized as a bi-level image for ArcScan to function correctly. Right-click on the raster layer in the table of contents (left panel), choose Properties, and click on the Symbology tab (Also see the Symbology tutorial for general information). On the left, choose Unique Values. Only two colors should be shown. If there are more than two, remove the extra colors such that only the background and the color representing desired features are remaining.

To use ArcScan to trace rasters, the ArcScan toolbar needs to be opened and an editing session needs to be started (See the Editing Data Tutorial). To open the ArcScan toolbar, go to Tools > Customize. Then, go to the Editor toolbar and click on Editor > Start Editing. Functions on the ArcScan toolbar should now be active. Activate raster snapping by going to Editor > Snapping and choosing from the Raster group at the bottom. If you are tracing lines, definitely activate Centerlines, and possibly Intersection and Corner. Next, make sure the Target layer where the new features are to be created is selected on the Editor toolbar.

To start a trace, select the Vectorization Trace tool , snap to a starting location, and click. Point the tool in the general direction of the next line, and click. ArcScan will automatically trace another segment. Continue tracing until the feature is complete, then press F2 to finish. A new feature has now been digitized into the map layer.

This tutorial has outlined the basics of using an ArcScan tool to vectorize features from a raster image. For more detailed directions and advanced tools, see the ArcScan tutorial from the ESRI Documentation Library.