Automated raster-to-vector programs are limited by the ability of the software to make decisions that require human intelligence. For example, automatic raster-to-vector conversion does not offer editable text, layering, associative dimensioning, or adherence to any office standards.

Each has its own shortcomings, however, these are some of the areas where the technology is limited and professional input typically is required:

Arcs and Circles

Arcs and circles are converted to a series of short, unrelated line segments and therefore will behave as such when manipulated. Special treatment often is required because the source for original hand drawn circles is actually elliptical.

Attributes

Attributes or database information cannot be assigned with automated conversion processes. This greatly reduces the value of the drawings for future CAD and GIS work.

Colors and Gray Scales

CAD and GIS conversion require high contrast originals. Color maps cause a problems that must be interpreted by professionals.

Contour lines

Where as most conversion processes handle straight lines easily often most have difficulty reproducing a series of contour lines. Contour lines must be preset and adjusted during the conversion process slowing the efficiency of the overall effort.

Conversion of Extraneous Information

In addition to the problems associated with correctly converting real data into CAD and GIS files, every smudge, crease, speckle or stain also has the potential of finding its way into the converted drawings.

Dimensions

Dimensions are converted to an unrelated assortment of lines with no association to each other or to the items they describe.

Gaps

Imperfections, light or thin areas in lines on the original drawings are frequently interpreted as white space. The result is often a continuous line that is broken into unrelated segments because of the conversion process. Each drawing has to be reviewed to make sure all contiguous lines are true.

Hatch Patterns

In some cases, hatch patterns are treated line enormous numbers of unrelated line segment, will be difficult to manipulate and can greatly reduce the efficiency of the file's performance in terms if storage and output.

Layering

Depending upon the drawing, the number of layers comprising finished CAD and GIS files can be numerous. Typically, automated conversions put all of the information on a single layer, or, some will put each line weight on a different layer, but only, if there is a clear difference in line thickness.

Linetypes

Any non-continuous linetype such as a dash or segment is converted into a separate and unrelated line entity.

Missing Information

The tendency for automated conversion programs is to omit information that it doesn't understand. Often this results in arbitrary elimination of real data in the converted drawing.

Noise

Vector entities created from map text are often treated as noise to and often deleted from finished GIS conversions.

Style

Automated conversion processes often are incapable maintaining style within each file and within a group of files. Dimensions, symbols, borders, title blocks, text heights, fonts, text often need to be reworked for consistency and aesthetics.

Symbols

Symbols are often limited to libraries installed in the conversion process and are processed in a "best match" mode. In a worst case scenario, the symbols can be converted to numerous unrelated line segments.

Text

Text is often converted as many small line segments and therefore virtually impossible to edit. Some applications offer Optical Character Recognition (OCR) functionality but is limited. In a case where the OCR functionality is 98% accurate, one out of fifty characters can be assumed to be wrong and careful review is almost always necessary.