Setup & Recommended Settings for ArcScan

(Interactive Method for Tracing Lines from a Scanned BW Contour Map)

 

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See also ArcGIS Help: Contents / Extensions / ArcSCan

See also J:/saldata/ESRI_misc/esri_books/Using_ArcScan_for_ArcGIS.pdf

 

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In ArcMap:

 

From Tools Menu, choose Extensions. check box next to ArcScan

From View Menu, choose Toolbars, check ArcScan

From View Menu, choose Toolbars, check Editor

 

Add Data – browse to and add the scanned_map

        Change Symbology to Classified (0 and 1, BW)

        Symbology has to be bi-level (two colors only), it can also be Unique Values, 0 & 1,

            but cannot be Stretched.

        This is typically set to Black (or some other color of choice) and White (or Clear)

 

Add your Line (whatever your line file is named, referred to here as Line) shapefile (or create a new one if need be)

 

On the Editor toolbar main dropdown list, choose Start Editing

        Make sure that your <Line> shapefile is the editing Target

        Make sure that Create New Feature is the editing Task

        From the main dropdown list, choose Snapping…:

                Check End for <Line>  (under Layer, upper Snapping box)

                Check Centerlines and Ends under Raster (lower box)

 

Note that the ArcScan tools do not become active until you begin editing your Line file

 

On the ArcScan toolbar:

        Make sure that the Raster target is set to your scanned_map

        Choose Vectorization Settings from the Vectorization menu:

                For Intersection Solution, choose None

                For Maximum Line Width, enter 10

                Remaining default settings can be left as is

                Click Close to close the Vectorization Settings dialog box

 

Using the Vectorization Trace tool:

        Zoom in as needed to the area where you wish to begin tracing

        Click once on the Vectorization Trace tool (icon with green lines and a black arrow)

        Click once on a scanned contour line where you want to start tracing

        Click once more on the same contour line in the direction you want the trace to go (the line should be traced automatically until the end of the line is reached or an intersection or break in the line is encountered)

        If the end of a scanned line is reached (when done tracing), right click and choose Finish Sketch

        If an intersection or a break in the line is encountered (tracing has stopped), zoom in as needed (you can use any of the zoom methods while still in the trace mode, if you use a zoom tool you will need to click once on the Vectorization Trace tool again to re-activate it before continuing with the trace).

        To span a break in the line:

o     Hold the S key down (to Suspend automatic tracing)

o     Click once on the point where you want to continue the line (the other side of the break)

o     Release the S key and click once more on the line in the direction you wish the trace to proceed

        To proceed thru an intersection:

o     Either use the S key method (as with a break in the line) to suspend the trace so you can manually digitize your line across the intersection before proceeding with the trace... OR:

o     Sometimes (for a simple intersection without other intersections nearby) you can simply click once more with the trace tool on the other side of the intersection in the direction you want to go and the trace will pick up and continue… The risk of this method is that it might go down the wrong trail… or not work at all, in which case you will get an error message instructing you to use the S key to suspend tracing.

 

If a trace goes the wrong way (down a path you do not want):

o     Zoom in as needed

o     Hold the trace cursor directly over a vertex along the path you didn’t want

o     Right click and choose Delete Vertex

o     Continue manually deleting vertices one by one until you are back to the main path you wanted to follow

o     Use the S key to suspend tracing and manually digitize the line where you want it to go (past the bad spot)

o     Release the S key and click once more on the line in the direction you wish the trace to proceed

 

To continue with a completed line (extending an existing line using the trace tool):

o     Zoom in as needed

o     Hold the trace cursor directly over the end of the existing line (the point where you want to connect your new line to)

o     The cursor should ‘snap’ to the end of the existing line

o     Click once to begin your new line, then continue as usual

o     When you have completed your new line, use the Select tool (black arrow) from the Editor toolbar to select both the old and the new line segments that you wish to combine

o     From the Editor toolbar main dropdown menu, choose Merge (choosing whichever feature you wish as the one to preserve the attributes for, probably the older line feature, assuming it already has the elevation attributes added)

 

Cleaning up minor tracing errors:

o     Zoom in as needed

o     From the Editor toolbar, choose the Select tool

o     Double click with the Select tool on the line to be edited (this should select the line feature and show the vertices)

o     Using the Select tool you can now select and move a vertex

o     Holding the Select tool over an existing vertex, you can right-click and Delete Vertex

o     Holding the Select tool over the existing line at a location you wish to add a vertex, you can right-click and choose Insert Vertex (which can then be moved as needed)

o     Click once off of the line to complete the sketch

 

Adding Attributes

o     From the Editor toolbar click on the Attributes icon to open the Attributes dialog box

o     Enter elevation and/or other attribute information after finishing a line (while it is still selected)

o     Attributes can also be entered for any feature by selecting it with the Select tool

o     Attributes can also be entered by opening the Attribute table for the shapefile and typing directly into the field(s)

 

Save your Edits

o     From the Editor main dropdown menu, choose Save Edits (or Stop Editing)

 

 

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