GV FAE Knowledge

Article ID: GV4-19-06-14
Release Date: 06/14/2019

Applied to
GV-PC LPR (GV-DVR / NVR / VMS), GV-LPR1200, GV-DSP LPR

Common Misrecognition
Below is a list of examples of characters prone to misrecognition. Summary
The accuracy of all LPR engines is heavily dependent on the readability of the license plates being recognized. Henceforth, LPR accuracy may very well be affected by, to a certain degree, a variety of environmental and/or situational factors, which are exemplified by but not limited to the list below:

• View angle and distance of the LPR camera relative to the license plate
• Lighting and exposure condition of the license plate
• The design and arrangement of the license plate (colors, font, logo location, etc.)
• The condition of the license plate (cleanness, neatness, wholeness, etc.)
• The weather condition of the LPR site (rain, snow, fog, etc.)

All in all, it is implausible for any LPR system to have a 100% accurate recognition rate.
In the GV-LPR Camera Installation Guide, you can find six common scenarios, namely Large roll, yaw and pitch angles, Overexposed images, Blurry images, Low image contrast, Hollow characters, and Plate under shadows, that may cause LPR misrecognition, along with their solutions outlined.

Suggestions for Resolving the Misrecognition
Certain functions provided by GV-ASManager / GV-DSP LPR / GV-LPR1200 serve as workarounds for these misrecognitions.

1. Limiting Misrecognition between Numbers “1, 0” and Letters “I, O, Q”

For GV-PC LPR
On GV-ASManager, click Setup > Devices. From the Device List, select the desired LPR and select a Lane tab on the LPR Setup dialog box. Then enable the following features as needed:

• Replace all I with 1: Always identify letter ‘I’ as number ‘1’
• Replace all Q with zero: Always identify letter ‘Q’ as number ‘0’
• Replace zero with O: Always identify number ‘0’ as letter ‘O’

For additional details, see 13.2.3 Step 3: Configuring a Channel, GV-ASManager User’s Manual.

For GV-LPR1200 / GV-DSP LPR
Log onto the device’s Web interface. Go to Video and Motion > Recognition Engine Settings. Then enable the following features as needed:

• I with 1 Enable: Always identify letter ‘I’ as number ‘1’
• 1 with I Enable: Always identify number ‘1’ as letter ‘I’
• 0 to O Enable: Always identify number ‘0’ as letter ‘O’
• Q to 0 Enable: Always identify letter ‘Q’ as number ‘0’

For additional details, see 4.1.7 Recognition Engine Settings, GV-LPR1200 User’s Manual and 4.1.3 Recognition Engine Settings, GV-DSP LPR V3 User’s Manual, respectively.

2. Fuzzy Comparison

For GV-PC LPR
On GV-ASManager, click Setup > Devices. From the Device List, select the desired LPR and select a Lane tab on the LPR Setup dialog box. Then select one of the following as the Matching Mode as needed:

• Allow 1 mismatched character: Recognition results can tolerate 1 mismatched character not being the first or the last character
• Allow 2 mismatched characters: Recognition results can tolerate 2 mismatched characters not being the first and/or the last characters

For additional details, see 13.2.3 Step 3: Configuring a Channel, GV-ASManager User’s Manual.

For GV-LPR1200 / GV-DSP LPR
Log onto the device’s Web interface. Go to Events and Alerts > Registry Database. Then select one of the following options for Registry Database Comparison as needed:

• Like (One Character Mismatch): Recognition results can tolerate 1 mismatched character not being the first or the last character
• Somewhat Like (Two Characters Mismatch): Recognition results can tolerate 2 mismatched characters not being the first and/or the last characters

For additional details, see 4.3.10 Registry Database, GV-LPR1200 User’s Manual and 4.3.5 Registry Database, GV-DSP LPR V3 User’s Manual, respectively.

3. The Ultimate Solution
For optimal accuracy rates and door/gate control with high precision, it is recommended to install GV-AS1520 and/or GV-RU9003 with UHF tag as your ultimate solution.

For details, refer to the product pages below:
GV-AS1520
GV-RU9003