2011

■ When you finish digitizing a segment, mark it on the paper map so you
do not repeat the digitizing. Double digitizing increases file size.
Digitizing Topology
When digitizing data that will be used to create a topology, follow these
principles to achieve the most accurate results.
■ Boundaries (or other polylines) should be completed with the Near,
Intersection, or Endpoint object snaps to ensure that closed areas such as
parcels, buildings, and water bodies are in fact complete polygons.
■ Line segments should be snapped to existing end points where they
intersect.
■ When you are digitizing data for network topology, do not duplicate
objects. For example, do not double-digitize boundary lines separating
adjacent polygons. It's better to digitize adjacent polygons on the same
layer with common lines defining common boundaries. If one edge serves
two or more purposes, digitize the line once, then use the COPY and
CHPROP commands to put a duplicate line on a different layer.
After you digitize the linear elements that form the basis of the topology, you
should
clean up any problems (page 767) before you create the topology.
Digitizing Control Data Points and Monuments
When you are trying to match digitized maps with existing digital maps, you
can use some known-to-be-accurate points common to both maps.
■ Control Data Points — A system of geodetic control points covers the
entire United States. The latitude and longitude, and often elevation, are
established for these points. Similar systems exist for other countries, such
as Bench Marks and Trigonometry Points throughout the United Kingdom.
■ Monuments — If you are working with maps for a city or county, points
used for establishing locations for all maps probably already exist: these
points can include features such as public buildings, hill summits, and
parts of highways.
When you are digitizing a map, use the following procedures to establish
known control points:
■ Create a layer called REFERENCE. On it, digitize at least four points
corresponding to real-world coordinates such as the coordinate intersections
Overview of Digitizing Maps | 1077