Skew Mark Implementation

Scantron scanners and ScanTools Plus software support skew marks printed on sheets. Skew marks are black ovals printed on a sheet to provide additional sheet skew detection to the scanning software. They are designed to detect paper stretch problems due to lack of proper paper conditioning or other reasons.

General Requirements

Skew marks are optional.

Skew marks are not supported by the Download Plus Utility. Applications loaded into a scanner with Download Plus will ignore all defined skew marks. Scanning will occur as if no skew marks were defined in the application.

Each sheet of a document can have a maximum of 6 skew marks; for a dual-sided sheet, 3 skew marks per side are recommended (although the actual limitation is a total of 6 for both sides).

Skew marks must be printed to scan at a read level of 10 or greater.

The skew mark read level is not user-defined.

A skew mark can be defined in the same location as a form ID mark, if absolutely necessary. Because skew marks must be at a read level 10 or greater, and form ID marks can be defined as low as a read level 6, see the Scanning description below for how error reporting is handled during scanning.

Application Definition

If the scanner is an image scanner, and OMR from Image is used in the Application Settings dialog, Enable Image in the Application Settings dialog must also be selected for the sides of the sheet that contain skew marks.

Skew mark locations for each side of each sheet must be defined manually using the Add Skew Mark dialog. Skew marks are not automatically defined when using the Scan Sheet/Scan All buttons or by adding a background form image file.

See the Add Skew Mark dialog for recommended locations, it depends on the read cell spacing.

When defined, a skew mark appears as a green square in the grid definition area of the Application window. The exception is if a form ID is defined in the same location, then the form ID appears as a red square, and the green form ID is not displayed.

When skew marks are defined, and you use the Scan Sheet button when working on the application, if the skew marks are not at read level 10, the Scan Error dialog shows "Skew Mark detection error".

Scanning

Skew marks must scan at a read level of 10 or greater. If not, scanning stops and the Scanner Error dialog shows "Skew Mark detection failure". If a skew mark is defined in the same location as a form ID, a Form ID error may be displayed instead, see the description below:

• Form ID value defined as 6 through 9: If the mark reads less than the defined form ID value, the Form ID detection error appears; a Skew Mark detection error is not displayed. If the mark reads at or above the defined form ID value (passes the Form ID check), but less than 10, a Skew Mark detection error appears.
• Form ID value defined as 10: If the mark reads less than the defined form ID value of 10, the Form ID detection error appears; a Skew Mark detection error is not displayed.