Different Types of Digitization Errors in GIS

Digitization is a process of converting existing maps to digital form (Vector Format) by tracing the features.

Digitization can be done in two ways:

  • Heads-up digitization (on-screen digitization)
  • Heads down digitization (Tablet digitization or manual digitization)

Digitizing involves the interpretation of geographic features via the human hand, therefore, several types of errors can occur during the course of capturing the data.

The types of errors that occur during digitization are described below:

Overshoots and Undershoots

These types of errors occur when the line being digitized doesn’t connect properly with the neighboring line it should intersect with.

Overshoot occurs when the line digitized identifies a point of interest too far away from the feature.

Undershoot occurs when the system identifies a point of interest too low from the feature.


Dangles also known as dangling nodes are the lines that are not connected but should be, which causes to create a gap between the lines. Also, dangling nodes may occur when a digitized polygon doesn’t connect back to itself, which leaves a gap at a point where the two end nodes should have connected. This creates an open polygon.


Switchbacks, Knots, and Loops

These errors may occur due to an unsteady hand of a user as a result line being digitized ends up with extra vertices and/or nodes.

In Switchbacks, due to extra vertices, polyline formed with a bend.

In knots and loops, the line folds back onto itself.


Silver Polygon

Silver Polygons are errors formed between adjoining polygons overlapped by any other polygon. It can be prevented by the use of fuzzy tolerance during the overlay process.

Figure shows Silver Polygons and corrections
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