Digitizing and Analyzing Data
Prepared by:
John McGee
Jennifer McKee
With support from:
NSF DUE-0903270
in partnership with:
Geospatial Technician Education Through Virginia’s Community Colleges (GTEVCC)
• To learn techniques for generating new
spatial features in a layer.
• To learn techniques for including nonspatial data in your final Map Layout (for
example, graphs and reports)
New Techniques Covered
Working with raster data
Digitizing from digital imagery
Adding X,Y data to a map document
Buffering layers
Creating a report
Creating a graph
Adding a graph to a Map Layout
• Method of converting information from
one format to another using a trace
• Traditionally, digitizing has meant the
creation of a spatial dataset from a
hardcopy source such as a paper map or a
• The “old way”
Heads-up Digitizing
• Uses on screen digitizing, usually with an
aerial photograph in the “background”
• You are no longer bent over a digitizing
table (hence “heads up”).
• ArcGIS provides several tools to support
Digitizing Data
• Most vector spatial data
has been digitized from
paper maps and aerial or
satellite photographs.
• Digitizing data involves
placing a map or photo
on a digitizing table and
tracing features.
– Heads-up digitizing is
digitizing on your monitor,
not a tablet.
Digitizing Without Tracing
• Features can also be digitized without
– ArcGIS has several tools for creating circles,
rectangles, curves, and other shapes of exact
• You can specify angles and lengths of line
• You can specify that line segments be
perpendicular or parallel
• Points are features with no parts.
– They can be digitized with a single click.
• Lines have a beginning and ending, and
often change direction.
• Polygons are lines that return to their
• The points where a line begins and ends is called an
• The points where a line changes direction or is
intersected by another line are called vertices.
• The segments between vertices are called edges.
Endpoints (in red)
Vertices (in green)
Digitized Line
Edit Sketch
• A feature that has its vertices, edges, and
endpoints visible. Once the feature is
saved, the vertices, edges, and endpoints
disappear and it is no longer an edit
Edit Session
• All digitizing is done during an edit session.
– Task: operation you want to carry out
– Target: layer in which features are being digitized
– Tool: software function for completing the task
• 9 Tools for drawing edit sketches
– Grouped on a drop-down tool palette called the
Sketch Tool
Sketch Tool
Sketch Tool
• Creates new features within point, line, and
polygon layers
Sketch Tool
Midpoint Tool
• Lets you define the location of the next vertex by
clicking two points; the new vertex is placed at
the midpoint of the line between these points.
– Example → Roads
Midpoint Tool
Distance-Distance Tool
• This tool lets you create a point or vertex at the
intersection of two distances from two other
– Creates two circles based on two distances and finds two possible
intersection points where the primary can be placed.
Distance-Distance Tool
Direction-Distance Tool
• Allows you to create a vertex using a distance from a
known point, plus a direction from a known point to
define a bearing line.
– For example, a pole might be located at a specified distance from
the corner of one building, and at a defined angle from the
corner of another building.
Direction-Distance Tool
Trace Tool
• Helps you create new segments that follow
along existing segments.
– Essentially creates parallel line segments
Trace Tool
Tangent Curve Tool
• Adds a segment that is tangential to the previously
sketched segment.
– This tool is practical when sketching rail lines in which the
curves are nearly always tangential to the previous segment.
Tangent Curve Tool
Arc Tool
• The Arc tool helps you create a segment that is a
parametric (true) curve.
Arc Tool
Intersection Tool
• The Intersection tool creates a vertex at the place where
two segments would intersect if extended far enough.
Intersection Tool
Endpoint Arc Tool
• Allows you to specify the start and endpoints of the
curve, then define a radius for the curve.
– This is particularly useful in sketching cul-de-sacs, where the
beginning and ending points of the arc, as well as the radius of
the cul-de-sac, are known.
Endpoint Arc Tool
Undo Mistakes
• You can undo digitizing mistakes with the
Undo button on the Standard Toolbar.
• Or you can use ctrl-z

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