Coordinate Geometry (COGO): involves entering survey data using a keyboard. From these data
the coordinate of spatial features are calculated. This produces a very high level of precision and
accuracy which is needed in a cadastral system.

For a city with 100,000 parcels, it would cost approximately $1 - $1.50 per parcel or $100,000 to
$150,000 to digitize the parcels manually. COGO procedures are commonly 6 times and can be up
to 20 times more expensive than manual digitizing.

Surveyors and engineers want the higher accuracy of COGO for their applications. Planners and
most others are happy with the lower accuracy provided by manual digitizing.

Manual Digitizing: The most widely used method for entering spatial data from maps. The map
is mounted on a digitizing tablet and a hand held device termed a puck or cursor is used to trace
each map feature. The position of the puck is accurately measured by the device to generate the
coordinate data.

Digitizing surfaces range from 12 inches x 12 inches (digitizing tablet) to 36 x 48 (digitizing table)
and on up.

The digitizing table electronically encodes the position of the pointing device with a precision of a
fraction of a millimeter.

The most common digitizer uses a fine wire mesh grid embedded in the table. The cursor normally
has 16 or more buttons that are used to operate the data entry and to enter attribute data.

The digitizing operation itself requires little computing power and so can be done without using
the full GIS. A smaller, less expensive computer can be used to control the digitizing process and
store the data. The data can later be transferred to the GIS for processing. The problem with this is
having enough software for all the computers.

The efficiency of digitizing depends on the quality of the digitizing software and the skill of the
operator. The process of tracing lines is time-consuming and error prone. The software can provide
aids that substantially reduce the effort of detecting and correcting errors.

Attribute information may be entered during the digitizing process, but usually only as an
identification number. The attribute information referenced to the same ID number is entered
separately.

Manual digitizing is a tedious job. Operator fatigue (eye strain, back soreness, etc.) can seriously
degrade the data quality. Managers must limit the number of hours an operator works at one time.
Acommonly used quality check is to produce a verification plot of the digitized data that is visually
compared with the map from which the data were originally digitized.

Scanning: Scanning provides a faster means of data entry compared to manual digitizing.