Carrida Edge Installation Guide

1   Carrida Edge Installation Note for access control

Copyright:1996-2018 Carrida Technologies GmbH, Ettlingen, Germany
Author:Carrida Technologies

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1.1   Introduction

This manual describes the installation of the Carrida Camera for access control and parking.

See also the related documents for further details and technical information:

A list of abbreviations used throughout this document

Automatic License Plate Reader.
Stands for processors with the v8 AARCH 64-bit instruction set.
Stands for processors with the v7 ARM 32-bit instruction set.
Decibel, used to describe a relative sensitivity (gain) value in cameras.
Frames per second.
Field of view.
License Plate.
Milli-Ampere, one 1/1000 th of an ampere.
Millisecond, one 1/1000 th of a second.
Personal Computer.
Product Key (for software licensing).
Pixel. The smallest unit of resolution in an image. For example, VGA images are made up of 640x480 pixels.
Region of Interest, typically a marked area in an image.
Software Development Kit.
Stands for Processor Architectures with the Intel instruction set. 32-bit hardware.
Stands for Processor Architectures with the Intel instruction set. 64-bit hardware.
Vision Components GmbH.
On-screen display

Image symbols used in this document

Symbol Meaning
Note Sign Points to especially important aspects of the manual or the software.
Hint Sign The lightbulb highlights the hints and the ideas that may be helpful.
Warning Sign This warning sign alerts of possible pitfalls to avoid. Please pay careful attention to sections marked with this sign.

1.2   Carrida Camera properties

The Carrida Camera is equipped with a 8 mm lens by default, the resulting horizontal field of view is suitable for most access control applications. The viewing angle with the 8 mm lens is 30° horizontally and 20° vertically.

The working distance of the Carrida Camera ranges from 2-8 m. It is recommended to switch the camera to high resolution mode if its needs to read at distances above 4 m. This doubles the resolution of the image and enhances the reading capability accordingly. You can change this setting in the Camera Configuration page by turning off the low resolution flag (see Carrida Camera Program User Documentation).

Table 1 below shows the field of view (width of the observable area) depending on the distance of the vehicle from the camera. The field of view is independent of the low or high resolution setting.

Table 1: The field of view at different distances for an 8 mm lens.
Distance Field of View  
2 m 1.25 m  
3 m 1.88 m
4 m 2.50 m
5 m 3.13 m
6 m 3.75 m
7 m 4.38 m
8 m 5.00 m

If the Carrida Camera is equipped with a 12 mm lens, the field of view is better suited for longer distances. See the following Table 2.

Table 2: The field of view at different distances for a 12 mm lens.
Distance Field of View  
4 m 1.67 m  
6 m 2.50 m
8 m 3.34 m
10 m 4.17 m
12 m 5.00 m
14 m 5.84 m
16 m 6.67 m

1.3   Getting Started

Install the camera according to the given limitations:
  • The viewing angle from the camera to the license plate should not exceed 30° in any direction.
  • The field of view of the camera is 30° horizontally, and 20° vertically (table above).
  • The camera should be mounted at least 2 meters from the expected closest position of a license plate.
  • Plates can be rotated with an angle as much as 20° clockwise or counterclockwise.

For best reading results, it's recommended to mount the camera on a minimum height of ca. 80cm. This avoids the disturbance of the vehicle headlights shining directly into the camera, which otherwise might reduce the image quality when the vehicle is very close to the camera.

After mounting the camera, connect the power and the LAN cable. Open a web browser (e.g. Opera, Firefox) and use the default IP address in order to access the configuration page of the device.


Note Sign The default IP-address of the camera is

On the configuration pages of the camera, you can modify its setup and see a live image and reading results.

During and after configuration, the best practice is to test the camera: drive a vehicle into the position where it should be possible to read the plate and check the reading results.

1.4   Mounting the camera

The camera should be mounted and stabilized on a place which is least 2 meters away from the closest position where the vehicle is expected. Closer distances can work, but the reading accuracy may be less in those situations.

The best recognition distance is between 2 and 8 meters. The camera should be installed by keeping in mind the angle and distance limitations as described in following paragraphs.

1.4.1   Limitations to be considered

The camera has a field of view (FOV) of 30° (A) horizontally and 20° (B) vertically, as shown in Figure 2.


Figure 2: The field of view of the Carrida camera when equipped with the standard 8 mm lens.

As a further consideration, the angle between the plate surface and the camera should not exceed 30° in any direction in order to obtain the best reading results. Figure 3 gives an example of an installation where the camera reaches the limit of 30° horizontal (A) and 30° vertical (B) viewing angle.


Figure 3: Requirements for the camera position.

Lastly, the rotation angle of the license plates must not be greater than 20° clockwise or counterclockwise as shown in Figure 4.


Figure 4: The angle of the plates must not exceed 20° clockwise or counterclockwise.

1.4.2   Mounting directly at the gate

The Carrida camera can be mounted directly by the barrier pole, either in front or behind it, with an unobstructed view of the vehicle plates. If the camera is mounted directly at the gate, it can be positioned at bumper level height (ca 0.50 m). The horizontal angle, in this case, will be reduced to the minimum, as shown in Figure 5.

Make sure that the camera is protected from the vehicles, and has an unobstructed view, without any objects that could get in the way.


Figure 5: ALPR mounted on a bumper level behind the gate (A), and in front of the gate (B).

We recommend for the Carrida camera to be mounted a few centimeters above the level of the headlights of the oncoming vehicles. This reduces the glare of the headlights into the lens and thereby minimizes flares, which could affect the image quality. In the following Figure 6 the camera is positioned with a slight angle to the plates (15°), above the direct beam of the headlights.


Figure 6: The Carrida camera mounted on a pole above the vehicle headlights at approximately 80 cm elevation above street level.

1.4.3   Mounting on a pole / elevated position

It is possible to mount the Carrida camera on a higher position, as shown in Figure 7, but this may limit the useful range within which license plates can be read.


Figure 7: The Carrida Camera mounted on a 2.2 m high pole behind a barrier.

From this height and perspective, the Carrida camera recognizes vehicles resp. their plates, which are more than 4 meters away from its position. Tilting the camera further down would make the viewing angle to the plates too steep (more than 30°), and as a consequence decrease the reading performance. See the following Figure 8.


Figure 8: Vehicle approaching closer to the barrier.

1.5   Setting up the camera

After connecting the camera to a PC or laptop, open a web browser and enter its default IP-address in the address bar (the IP address of the camera can be changed in the setup).

The main page of Carrida Camera Configuration will open as shown below.


Figure 9: The main Carrida camera configuration page

The Carrida Configuration page has the following menus:
  • Home
  • Live Result
  • Text Result
  • Access
    • Actions
    • Lists
  • Settings
    • Camera
    • LED Flash
    • Server
    • Trigger
    • Mode of Operation
    • Engine
    • Access Control
  • Configuration
    • Network
    • Time
    • Users
    • Classifier
    • System
  • Documentation
  • Log Out

Detailed information about how to setup the Carrida Camera using the configuration pages can be found in the Carrida Camera Program User Documentation.

1.5.1   Adjusting the camera exposure control

The second important aspect that needs to be taken into consideration while installing the camera is the correct adjustment of the exposure and the brightness settings. Every camera setup is different and the automatic brightness control of the camera needs to be adjusted according to its mounting position and viewing angle with respect to the lane or barrier.

The Use Brightness control found in the Settings tab under Camera parameters are used for this purpose. It is important to properly set these values, as they will substantially influence the quality of the license plate reading results by avoiding overexposed or underexposed license plates. It is recommended to leave this parameter on at all times, as it will enhance the image quality.

The camera automatically controls its exposure based on the brightness measurement in the live video, constrained by minimum/maximum values for exposure. The most important setting is the area, where the camera measures the current image exposure - this area should cover only the region of the image that contains or will contain a license plate. The image area, which is used for measurement and control, is called the Brightness control polygon. The area enclosed by the green polygon is called Brightness control region and it will be affected by brightness control parameters.

In the image below, the brightness control polygon is drawn by green lines. The polygon corners can be moved by clicking and dragging them to the desired location in the image and saving the changes by clicking the Apply option on the right side of the menu.

It is important that this region has the smallest possible dimensions, yet big enough to cover those parts of the image, where actual license plates will pass through.

Select the area where you expect the vehicle plates to appear, as shown in the image below.


Figure 10: Limiting the brightness control polygon to the image area which can contain license plates.

By controlling the Minimum/ Maximum Gain and Minimum/Maximum Shutter options, the brightness of the image can be controlled. Example: Slow shutter speed produces brighter images because the time frame during which the light passes through is longer.


Note Sign Detailed information about the Minimum/ Maximum Gain and Minimum/Maximum Shutter options can be found in the Carrida Camera Program User Documentation, Sections 7.1.11- 7.1.14.

1.5.2   Basic Event configuration

ACCESS Configuration provides tools for controlled vehicle access, mainly the control of Lists and Actions. Three categories of lists are available: Whitelist, Blacklist and Ignorelist. Each of these categories supports importing and exporting of lists, as well as adding single entries. Formatted lists are used to prompt actions which can be defined in the Actions tab.

The Carrida Camera can be set up for specific actions, which take place after certain events (Read, NoRead, LCR) occur. For example, when a license plate has been read, the camera can automatically send the current license plate images to a specified ftp server.

To define actions for events, go to the ACCESS page and Actions tab. Carrida supports three types of events, which can trigger actions:

  • Read event (a LP has been read)
  • NoRead event (no LP has been found within a defined time limit)
  • Low Confidence Read (a LP has been read, but with low confidence)

Actions for certain events can be defined on the event drop-down lists under the Actions tab by clicking on the ADD option. click on ADD, and a list of actions will appear. Select any action and save your selection, as shown in the Figures below:


Figure 12: Actions


Figure 13: Creating an FTPDatabase action.

Following seven actions are available:

  • FTPUpload
  • FTPDatabase
  • Store
  • DigitalOut
  • Serial
  • TCP

The most common ones are FTPUpload and FTPDatabase. The former action executes the transfer of the last read image to a remote FTP server and the latter updates a csv file with all readings on a server.

When clicking on the selected action, a list of related parameters becomes visible. Different actions offer different sets of parameters.

  • Enable the action.
  • Enter the IP address of the host.
  • Enter the credentials in the following form: [username]:[password].
  • zExample: for the username "user123" with the password "pass123" the correct form is: user123:pass123
  • Assign a naming pattern which will be used for the filenames saved images.
  • Images can be uploaded as follows: empty file uploads, full image uploads or license plate image uploads.
  • Define the image quality for sent images (recommended cca 70%).

The option FTPDatabase has a similar set up to the FTPUpload action. When triggered, the Carrida Cam will create and update a text file containing information about the recorded vehicle number plates.

To create an FTPDatabase action:
  • Set enable to true.
  • Enter the IP address of the host of the FTP server.
  • Enter the credentials in the form of: [username]:[password].
  • Filename stands for the name of the database to be updated (created) with newly recorded information.
  • Assign a naming pattern under which the readings will be saved.

Actions can appear multiple times, and they can be combined with other actions. A detailed description of possible actions and their parameters can be found in the Carrida Camera Program User Documentation, Chapter 7.

Some actions offer a naming pattern field.

Naming patterns are used to specify which name ALPR should generate with the reading result, thus enabling the user to define filenames, which contain the date, time, plate numbers, and other information about a specific reading. They can be constructed using placeholders for specific information.

Placeholders are characters written between two percentage (%) symbols (see the example below). They are later substituted with specific information about a reading. File names can be formatted in many different ways using patterns whose complete list can be found in Carrida Camera Program User Documentation, Chapter 9.


A placeholder for the vlicense plate is %LP%, for the date is %DAY% %MONTH% %YEAR%, level of confidence for plate recognition is %CONF%. The camera detected a vehicle with number plate W223344 on the 03.08.2017, with a level of confidence 98%. The following naming patterns can be formed

  • Naming pattern: Detected %LP% on %DAY% / %MONTH% / %YEAR% .
  • Output: Detected W223344 on 03 / 08 / 2017 .
  • Naming pattern: %LP%(%CONF%) on %DAY%/%MONTH%/%YEAR%.
  • Output: W223344(98) on 03/08/2017.
%LP% - license plate %CONF% - plate confidence
%STATE% - state %CONF_STATE% - state confidence
%DAY%.%MONTH%.%YEAR% - date %HOUR%:%MINUTE%:%SECOND% - time

1.6   Parking Mode

The Carrida Camera can be configured so that it either transmits every reading result directly to a client or to a connected application. In many situations this behaviour is undesirable, because only one good result is sufficient.

In parking mode, each vehicle number plate is required to be detected at least three times. The output result is available immediately afterwards and it consists of unique license plates. This mode is recommended for live streams and USB cameras.

The parking mode is found on the Settings page, Mode of Operation tab. Other than that mode, three further modes (Single images, Offline video and Free flow) are offered. Specifics can be found in Carrida Camera Program User Documentation, chapter 7.5.

How the parking mode works:

The purpose of the parking mode setting is to create a filtered unified reading for multiple readings of the same license plate. Only that one reading will be transmitted to a server.

When the Carrida Camera is operated in parking mode, it scans its field of view and tries to find license plates until a certain defined number of valid readings has been made. It then transmits the reading and waits until this license plate disappears.

The parameter Minimum Detections controls how many readings of the same license plate have to be made until a definite result is produced. Only after this number of readings the transmission of the result will take place. A new reading is accepted as valid if

  • The number of character differences to previously read strings is not greater than Maximum character Mismatch
  • If it is detected inside the ALPR region of interest (A formerly specified region, where the reading area for ALPR recognition is defined. Further information and settings in Carrida Camera Program User Documentation, chapter 7.3.9)

The parameter Maximum Characters Mismatch refers to the maximum amount of characters allowed to be different between two plate strings for them to merge. Recommended to be set to 1.

parking mode examples

The following examples clarify the use of the parking mode settings in more detail. Assuming that two vehicles enter the field of view of the camera, the following events may take place.

Example 1: For a setting of Minimum Detections = 2, Maximum Char Mismatch = 1

Time Reading Confidence Camera Action
09:00:02.0 123 40  
09:00:02.3 AB123 50  
09:00:02.6 ABC123 60 the camera has a valid result and transmits ABC123 with a confidence of 60
09:00:02.9 ABC123 50 all further readings will be ignored, no transmission
09:00:03.2     no license plate found
09:00:03.2     no license plate found
      no license plate found
09:00:08.1 OS456 50  
09:00:08.4 OS456 70 the camera has a valid result and transmits OS456 with a confidence of 70
09:00:08.7 OS456 60 all further readings will be ignored, no transmission

Example 2: For a setting of Minimum Detections = 3, Maximum Char Mismatch = 1

Time Reading Confidence Camera Action
09:00:02.0 123 40  
09:00:02.3 AB123 50 difference is greater than 1 to previous reading, first new reading
09:00:02.6 ABC123 60 difference = 1, second reading
09:00:02.9 ABC123 50 difference = 0, second reading, the camera has a valid result and transmits OS456 with a confidence of 60 (the biggest confidence found)
09:00:03.2     no license plate found
09:00:03.2     no license plate found
      no license plate found
09:00:08.1 OS456 50  
09:00:08.4 OS456 70 the camera has a valid result and transmits OS456 with a confidence of 70
09:00:08.7 OS456 60 all further readings will be ignored