Vehicle Counter
Contents
1. Beside real data these files also report application start and stop with the followings lines of text 2013 02 26 VehicleCounter stopped Tue Feb 26 11 42 27 2013 2013 02 27 VehicleCounter started Wed Feb 27 15 53 45 2013 Vehicle statistics instead are stored in lines of text with the following format YYYY MM DD lt probeIdx gt lt dataType gt lt data gt where 10 15 e mag ents softwarelab Vehicle Counter User manual e lt probeldx gt is a number identifying the probe that collected that data starting from 1 e lt dataType gt is a character identifying the particular type of data o jc vehicle count o v vehicle velocity o T vehicle length experimental e lt data gt is a comma separated list of integral numbers containing the actual data The meaning is dependant on the data type o jc lt data gt is a comma separated list of 1440 integral numbers the i th number being the count of vehicles detected by the probe during the i th minute of the day o WM lt data gt is a comma separated list of 20 integral numbers the i th number being the count of vehicle detected by the probe in the i th class of velocity 0 8 Km h 8 16 Km h 16 24 Km h 24 32 Km h 32 40 Km h 40 48 Km h 48 56 Km h 56 64 Km h 64 72 Km h 72 80 Km h 80 88 Km h 88 96 Km h 96 104 Km h 104 112 Km h 112 120 Km h 120 128 Km h 128 136 Km h 136 1442. Km h 144 152 Km h 152 160 Km h o T lt data gt is a comma separated list of 50 integral numbers the i th number being the count of vehicles detected by the probe in the i th class of length this is experimental will not be detailed In order to limit the number of data files on the camera file system new data files are only created monthly 7 4 Downloading alarms Beside data files VehicleCounter generates and stores alarms in similar text files that are listed in the Download section of the Configuration page Alarms files are similar to data files and look like this Feb 26 11 38 56 2013 1000 frames ago at Tue Feb 26 11 42 01 2013 1000 frames ago at Tue Feb 26 11 42 01 2013 Feb 26 11 42 27 2013 2013 02 26 VehicleCounter started Tue 2013 02 26 sensor 1 WARNING busy since 2013 02 26 sensor 3 WARNING busy since 2013 02 26 VehicleCounter stopped Tue Application start and stop event are logged in order to ease reading All other lines correspond to an 11 15 t X Vehicle Counter Fe Mm Q e A d User manual softwarelab equal number of alarms Alarms are generated to notify the fact that a sensor is not able to count vehicles because the application believe it is in busy state When a sensor remain in busy state for too long an alarm is generated and a line of text is added in the daily alarm log The number of frames that a sensor can remain in busy state before startin
3. always capable to restart autonomously with a valid configuration For this reason configuration changes are done in two steps At first the new configuration is encoded in XML and sent to camera which verifies its correctness Then if the new configuration is valid it is stored in the file system so that it becomes fully functional at the 8 15 t Vehicle Counter Ss Au Q enta User manual softwarelab next application restart If for any reason this process fails before the last step the application is capable to recover the previously used probes configuration and the attemptend configuration change is discarded Lind Load from camera ted Load from camera Editor Editor Editing Speed Probe 1 element 0 Editing Speed Probe 1 element 0 Out sensor Out sensor Manually set H Manually set Move First Comer x848 y 106 Resize Width 134 Height 32 Preview Setup CB Size 640x480 Resize Fps 1 Apply Preview Setup Figure 5 The Editor pane with text boxes for manual set of position and size folded left and unfolded right When the VehicleCounter Configuration Page is loaded in the browser a request for the current probes configuration is immediately sent to the camera server in order to draw the probes on the preview pane However the user can explicitly request to reload the current configuration from the running application by clicking the Load fr
4. license key There is a known bug in several Axis firmwares affecting several different camera models The bug regards a missing library link that prevents the application from finding a shared library at loading time This bug prevents the package from being accepted by the camera verification system and can only be fixed by Axis which is already informed by distributing a new version of the camera firmware to be installed onto the camera In the meantime Magenta srl has developed a patch that provides a workaround The patch is distributed as a stand alone ACAP application The user can download the patch EAP package visiting Magenta s website at http www magentalab it page id 189 This package must be installed as any other ACAP application and it will be listed in the Application packages page of the Axis camera server as Magenta patch However it does not need to be executed the application itself does not do anything and will terminate immediately if started As long as the patch is installed it provides the missing links to other ACAP application like VehicleCounter If this does not fix the problem contact Magenta srl Write a detailed e mail describing your problem your camera model and your camera serial number at magenta magentalab it 15 15
5. 5 t S Vehicle Counter Fe m Q enta User manual softwarelab 2 Automatic install If only a license code is available it can be used in the Automatic Installation section in order to receive the license key file directly from Axis To do this the user must insert the license code and a valid e mail address in the Automatic installation section of the License page of the VehicleCounter application By clicking Install these informations together with the camera serial number will be transmitted to Axis which will respond with a valid license key that will be automatically installed This method obviously requires that the camera is connected to the internet and is correctly configured AXISA AXIS M3204 Network Camera Live View Setup Help bBasic Setup Application Settings VehicleCounter OH Application Settings gt Video Main page gt Live View Config ener Not Running Parameter Settings PTZ fps 20 0 30 Applications resolution 320x240 Packages loginterval 60 1 3600 vVehicle Counter Settings httprequestrefresh 1 D et License framesbusybeforealamraised 1000 1000 About Save Reset gt Events gt System Options About Figure 3 The VehicleCounter Settings page Once a valid license key has been installed the application can be started see Section 5 4 Camera setup The VehicleCounter application is designed to work preferably from an elevated point of view Ideally the best ca
6. Ei Vehicle Counter Sp Magenta User manual softwarelab Vehicle Counter User Manual 1 15 DY Vehicle Counter p Mage nta User miannall softwarelab Index 1 Introduction eeh 3 PADAT EE 4 SEU e a Re A AAE EAA RE A e AOE E SAR SEEE REE 4 4 Camera SOUND E 5 5 Running and stopping the applications seet 5 6 Application E 6 7 VebicleCo nter Config ra ti n Eed bieten eh Cen 7 7 1 Configuring Eeer 7 Tid E 9 7 3 Downl ading EN 10 7 4 Downloading alanis a3c25sssvisncvancctnnssdasseonsaadecestaspatenstdeusaladucsvoniaudaientadpacchandaidaiasheasevectunseerapauseds 11 8 Programmable events s sseeeeessessesseessesseesoessrsseesoessrsseesoessesseesoesseesoessesseseoesserseesseessserssserereeeereses 12 IWED APL E 13 IR Kee sessirnir e acie ri e runer a ratar ee aiae aiae Reier o EEE eaei 14 2 15 softwarelab SS Vehicle Counter p Mage nta User mannal AXIS a AXIS M3204 Network Camera Live View Setup Help nai belie Application Packages OH gt Video Select package file to upload Choose File No file chosen and click Upload Package Up to 8MB gt Live View Config Installed Applications n Application Version Vendor Status License installed VehicleCounter T Magenta srl Not Running no vApplications Packages gt Vehicle Counter gt Events gt System Options About Start Stop Remove Log Figure 1 The Axis camera Application Packages page 1 Introduction VehicleCounter is a traffic monitoring a
7. as actually detecting a vehicle or a false positive occurred To react to the raise of an event either a stop event or an alarm event the user must add a new 12 15 Sa Vehicle Counter Se Mage nta User mannal softwarelab triggered eventi in the camera server event system In the section Events Event Types clicking the button Add triggered will show the page in Figure 6 There the user can decide 1 which name to give to the triggered event 2 the priority level with respect to the other events 3 the minimum time interval to wait after a trigger before the same event is allowed to be triggered again 4 aweekly schedule of time periods during which the trigger is enabled 5 which is the trigger 6 what to do when the event is triggered Point 5 is what makes the difference between VehicleCounter events and other events When VehicleCounter is running in the first combo box in the Triggered by section it is possible to choose Application trigger This will populate the second combo box with events defined by the currently running application For VehicleCounter possible choices are VehicleCounter stop and VehicleCounter alarm After that in point 6 the user can choose what to do when the event is triggered After checking out the desired options the page will show up additional controls based on the particular choice 9 Web API The VehicleCounter application defines sev
8. ckage downloaded in step 1 and click the Upload Package button 3 once installed the VehicleCounter application will be listed in the Installed Application section of the page as depicted in Figure 1 3 Licensing In order to be able to start the VehicleCounter application the user must install a valid license key file To obtain a license key the user must visit the Axis website at http www axis com techsup compatible_applications For a 90 days trial license key choose the Get Trial Key option select VehicleCounter from Magenta srl version 1 1 from the combobox and enter the serial number of your Axis camera For a commercial license key a license code must be requested to Magenta srl by writing to magenta magentalab it Then the full license can be downloaded by providing both the license code and the camera serial number in the Get Activation key section of the same web page remember to choose VehicleCounter from Magenta srl version 1 1 in the proper combo box The license key can be installed by accessing to the VehicleCounter License page see Figure 2 The camera interface provides the following installation methods for license keys 1 Manual install If a license key file is already available the user can upload it manually to the camera server via the License page of the VehicleCounter application Choose file and Install in the Manual Installation 4 1
9. der the Manually set button in the Editor section enter the desired values and click the Manually set button 7 2 Preview pane The preview pane shows live images from the camera sensor with the current configuration drawn on top of it Since it is likely that the VehicleCounter application will be configured with the camera already on site it is important for the configuration page to be usable even with low bandwidth connections For this reason the video stream played in the preview pane is a possibly low bitrate 9 15 DY Vehicle Counter p Mage nta User mannall softwarelab mjpeg stream The Preview setup section allows the user to choose the resolution of jpeg in the preview pane 640x480 320x240 160x120 and the frame rate of the mjpeg stream However the main purpose of the preview pane is to allow the user to draw the sensors on a reference image For this reason regardless of the chosen image resolution the preview pane will keep its original size of 640x480 pixels degrading image quality to ease the process of drawing the sensors Please note that the resolution at which the VehicleCounter application works may be different and can be changed in the application Settings page Below the area where jpeg images are displayed are placed two buttons that can be used to show or hide the live capture of data from the camera By clicking Show Probes Output the browser will start to rec
10. eive a textual stream with live information from the configured probes which will be displayed on screen The information received will look like shown below this example refers to the case of 2 probes 18129 Probe 0 65 4 40 km h Probe 1 58 3 60 km h 123 The first number is a frame counter In normal conditions of operation this number should be increasing Then for each probe a string of text is reported with the following format Probe lt ProbeIdx gt lt Count gt lt CountSinceLastMinute gt lt LastEstimatedSpeed gt e Probeldx is obviously the probe index Count is total number of vehicles counted by these probe e CountSinceLastMinute is a partial counter that is reset to zero every minute e LastEstimatedSpeed is the last estimated approximate speed Speed and Speed2 probes only Finally at the end of the line the total count of vehicles detected by all configured probes is reported The character pipe is used as a separator between strings from different probes 7 3 Downloading data The purpose of VehicleCounter is to collect statistics about the observed traffic flows These data are stored in text files on the camera file system that are listed in the Download section of the VehicleCounter Configuration page Figure 4 From there data files can be downloaded and deleted Data files are text files updated on a daily basis Each line of text has the format YYYY MM DD lt data gt
11. em Use 13 15 Ei Vehicle Counter p mage nta User miannall softwarelab with caution e http lt address ip gt local VehicleCounter eraseAlarmsFiles cgi Ask the VehicleCounter application to delete alarms files from the camera file system Use with caution 10 Troubleshooting 1 The sensors start counting a few seconds after the application has started and they do not start counting at the same time Why When the application starts configured sensors have to learn the background value of the signal extrated by the pixels so to be able to detect the variations due to the vehicles passing onto the sensors This process requires some time which is dependent on the local conditions of scene at each sensor During this time the sensor is not available for counting So some sensor could start counting immediately while some other sensor could start counting after a while 2 Some sensors do not seem to count at all There could be two reasons for this behaviour a Check the size of your counting sensor Sometimes a small counting sensor could be reduced a zero witdth or a zero height sensor when the 640x480 drawing on the preview pane is reduced to the size of the images actually used by the VehicleCounter which is likely 320x240 or smaller Try with a bigger counting sensor b The sensor cannot learn the background signal Sometimes it can happen that the sensor never reach its operational phase because it cannot lea
12. eral CGI that are used by the web interface to interact with the running application These CGI are public and can be used by other system to communicate with the web application What follows is a list of available CGIs e http lt address ip gt local VehicleCounter test cgi Test CGI that returns the probes output string e http lt address ip gt local VehicleCounter test2 cgi Test CGI that returns the probes output string in an autorefreshing web page The frequency of the refresh is specified by the httprequestrefresh parameter e http lt address ip gt local VehicleCounter getConfiguration cgi Return the probes configuration currently in use XML format e http lt address ip gt local VehicleCounter setConfiguration cgi Transmit a new configuration to the VehicleCounter application The new configuration must be included in XML format in a POST request to the CGI The request shall contain an option named xml and the option value shall be the XML document representing the new configuration e http lt address ip gt local VehicleCounter getDataList cgi Returns the list of data files available for download separated by semi colon e http lt address ip gt local VehicleCounter getAlarmsList cgi Returns the list of alarm files available for download separated by semi colon e http lt address ip gt local VehicleCounter eraseDataFiles cgi Ask the VehicleCounter application to delete data files from the camera file syst
13. g to generate alarms is defined in the Settings page framesbusybeforealarmraised In order to limit the number of alarm files on the camera file system new alarm files are only created montly De Event Configuration Triggered Event Type Setup AXIS P3301 Network C O 192 168 1 55 Triggered Event Type Setup New Event Normal _ Set min time interval between triggers 00 00 00 max 23 59 59 Respond to Trigger Aways Only during time frame Sun Mon Tue Wed Thu Fri Sat Start time booo Duration Bam max 168 00 hours Never event type disabled Triggered by Application trigger Y VehicleCounter alarm When Triggered Save stream Activate output port Send email notification Send HTTP notification to Send TCP notification Figure 6 The Triggered Event Type Setup page 8 Programmable events The VehicleCounter application generates two types of event that integrates perfectly the event management system of the Axis camera servers e stop event generated when VehicleCounter is stopped by a SIGINT e alarm event generated when a virtual sensor raises an alarm These events allow the user to schedule actions i e sending an email recording a video storing a picture when one of them occurs Alarm events are particularly interesting By scheduling the recording of a few frames of video in response to an event it will be possible to understand what made the sensor raise an alarm and if the sensor w
14. is not directly a sensor collection Rather it is a collection of elements where an element is a well defined set of virtual sensors and other information sometimes each with a specific function Sensors belonging to the same element provide data to a single application logic module that computes a single output for the whole element Since elements are grouped in probes the outputs of each element of a probe are grouped toghether to form that probe s output The fact that sensors are organized into elements gives the user more flexibility while positioning them In VehicleCounter there are three different kind of probes The structure of each probe s element and the number and usage of the sensors in the element are defined by the specific kind of probe 7 15 DY Vehicle Counter p Mage nta User miannall softwarelab e Counter Probe This is the simplest type of probe Its elements are made of a single virtual sensor which should be placed in the image so that it intercepts the passage of vehicles It is possibile to add how many elements as desired to the probe The output of the probe will be give by the sum of the vehicles counted by each element Speed Probe A slightly more complex probe Elements of a speed probe are made of two virtual sensor placed at a certain distance one ofter the other along the direction of motion of the vehicles When the user place a speed probe sensor he will be requested to place the first sen
15. lication Higher resolution means the application will process more pixels and this has an effect on performance The default is 320x240 loginterval time in seconds between two consecutive writes in the system log affects only the log of probes counting httprequestrefresh frequency in seconds at which the test page http lt camera ip gt local VehicleCounter test2 cgi will be automatically refreshed framesbusybeforealarmraised number of frames after which a busy sensor raise an alarm Also from the Settings page the user can access to the VehicleCounter Configuration page by 6 15 Sa Vehicle Counter Se Mage nta User mannal softwarelab clicking on the Main page link This will allow the user to configure the application by placing sensors and probes on the image frame 7 VehicleCounter Configuration Page The VehicleCounter Configuration page provides several key functionalities Figure 4 shows a screenshot of the page On the right hand side a customizable preview panel shows images taken from the camera sensor with the desired resolution and frame rate Being a preview panel both resolution and frame rate can be reduced to ease configuration procedure while using low bandwidth connections Currently configured virtual sensor are drawn super imposed on the camera image Note that the preview panel keeps its original size of 640x480 pixels even if the user choose a lower resolution the image quality is eventua
16. lly reduced This should ease the configuration of new virtual sensors as described below On the left hand side of the configuration page there are several sections From top to bottom e the tree like structure of the current configuration with controls for o adding Counter Speed and Speed2 probes o save the configuration to camera o load the configuration currently in use from camera controls to change resolutions and frame rate of the preview panel e controls to download and delete statistics and alarms log updated on daily basis 7 1 Configuring VehicleCounter VehicleCounter operations are rooted on the concept of virtual sensor A virtual sensor is just a rectangular sub image of the whole frame that defines what pixels the application will use to extract the signals upon which the application logic will infer the presence of a vehicle Virtual sensors are typically used in place of traditional loop wires but they can be used with different purposes not only vehicle counting In VehicleCounter virtual sensors are organized in a hierarchy At the top of the hierarchy there are probes A Probe is a set of virtual sensors whose data are grouped and analyzed toghether to achieve a single aggregated result For example if several counting sensors are added to the same probe the output of all the sensors will be summed up and the probe s output will be the sum of the vehicle s counted by each sensor However a probe
17. med in and out sensor respectively while the third sensor named counter sensor is use for counting only Usually the counter sensor is thinner with respect to the in and out sensor so to reduce the possibility that two vehicles could occupy the same sensor at the same time While this is not a problem for speed estimation it is undesirable in vehicle counting To detect the presence of the vehicle each sensor extract a one dimensional signal from the pixel values it includes The sensor is considered busy vehicle on sensor when this signal s value is above a certain threshold named top threshold in VehicleCounter To prevent the sensor from oscillating between busy and non busy states and to reduce false positives the one dimensional signal s value has to drop below a different threshold lower than the top threshold This one is called bottom threshold Both values can be changed in the tree like view in the configuration page Top and bottom threshold values are assigned to the probe and inherited by elements and sensors in that probe Once all the desired probes have been defined and placed the configuration can be saved to camera by clicking the Save to camera link at the bottom of the tree like view Since the VehicleCounter application is supposed to work outdoor and is likely to be not immediately at hand for maintenance it is important to ensure that the application is
18. mera setup is the one that guarantees an azimuthal view of the scene This ensures the lowest occurence of occlusions and lens distortions and the maximum accuracy in car detection and counting However this setup is often not achievable and the camera has to be placed in sub optimal positions VehicleCounter can work efficiently nevertheless provided that the actual setup gives limited prospectical deformation Performace will progressively degrade as long as camera elevation reduces In our test setup the camera is mounted at approximately 9 meters of height and observes a 4 lane road with an angle of about 45 In this conditions vehicle count proved to have an accuracy above 90 5 Running and stopping the application To run the application select it from the list in the Application Packages page of the camera server web interface and click the Start button see Figure 1 The application status should change from Not Running to Running To stop the application simply click the Stop button In case of power loss the VehicleCounter application will be restared automatically if it was running when the power failure occurred 5 15 Vehicle Counter Se Mage nta User miannall softwarelab Vehicle Counter Google Chrome D 192 168 1 54 i Dy magets softwarelab Configuration E Speed2 Probe 0 X Top Threshold 4 E Bottom Threshold 2 Speed2 Element 0 amp Sensor In Se
19. nsor Out 2 Distance 8 Sensor Counter Speed2 Element 1 amp Add new element Speed Probe 1 H Add Speed Probe Ha Add Speed Probe H Add Counter Probe jiri Save to camera Liri Load from camera Preview Setup Download Data files Alarm files o Hide Probes Output data2012 08 log _alarm2012 08 log Show Probes Output Hide Probes Outpt data2012 09 log alarm2012 09 log data2012 10 log alarm2012 10 log Delete data Delete alarms Version 0 5 Figure 4 The VehicleCounter configuration page 6 Application setup The VechicleCounter application can be setup entirely via the online web interface which is integrated with the Axis camera web interface Once the application is successfully installed a VehicleCounter menu voice will appeare under the Application menu in the left column of the Axis camera web interface By selecting it the user can access to the Settings and About pages The Settings page depicted in Figure 3 allows the user to provide a set of parameters that controls a few features of the vehicle counter application namely fps the frame rate at which the application grab frames from the sensor max 30 Keep in mind that frame grabbing on the camera is an independent process Grabbing frames at a frame rate higher than that the application can support will reduce the performance resolution resolution of the image grabbed by the app
20. om camera link at the end of the tree like view It has to be noted that the application responds to this request with the probes configuration that is currently in use retrieving it from memory regardless of the configuration stored in the file system For this reason even when a new configuration has been saved to camera it is still possible to recover the previous configuration just by clicking Load from camera followed by Save from camera The previous probes configuration only became unrecoverable after saving the new one with Save from camera Configured probes can always be corrected in position and size by clicking on the edit icon of a sensor in the tree like view The corresponding sensor in the preview pane will be redrawn with a dashed line and the Editor section appears below the tree like view The editor shows e A text string explaining exactly which sensor the user is editing e Controls text boxes for entering exact position and size of the sensor e Buttons to enable the move and resize mode To move a sensor from its current position click the sensor s edit icon in the tree like view click the move button in the Editor section and drag the mouse in the preview pane To resize a sensor follow the same instructions but click the resize button instead of the move button To enter exact position and or size for a particular sensor unfold the text boxes un
21. pplication developed on the Axis Camera Application Platform ACAP It can be installed on most of the ACAP enabled Axis camera server such as the P33 or M32 camera servers and it is capable of collecting meaningful statistics regarding the number of vehicles passing along the observed lanes and their estimated speed The application allows the user to set a number of virtual sensors and to decide how to aggregate the collected data by arraging sensors into probes Sensors configuration can be made by means of a web application which is installed on board and served by the camera web server Statistics are stored and made available for download on a daily basis The vehicle counter application is rooted on the concept of virtual sensors i e subregions of the whole frame which can be positioned across the monitored lanes crosswise with respect to the vehicle direction that select the image pixels to be processed for vehicle detection On each lane at least two sensors are usually palced most often three sensors are placed on each lane to be able to estimate the vehicles speed The main feature of VehicleCounter are e Real time estimation in each lanes of the following figures o vehicle per minute estimated accuracy on a real dataset 91 o distribution of the estimated speed The maximum number of observable lanes is only limited by the camera position and lens e Robustness to different light and weather conditions works cor
22. rectly day and night in sunlight cloudy weather or rain e Robustness to different traffic conditions works correctly with heavy traffic or vehicles standing in line e Optionally it can store images and video on SD card with a programmable time schedule 3 15 S magenta softwarelab gt Basic Setup gt Video Live View Config gt PTZ vy Applications Packages yvVehicle Counter AXIS M3204 Network Camera Vehicle Counter User manual Live View Setup Help License VehicleCounter 2 Installed license key Remove Manual installation To retrieve a license key for this application go to www axis com and enter your license code together with the serial number of this device This device s serial number is 00408CAC913E Settings License key file to upload Choose File No file chosen License About Install gt Events Automatic installation gt System Options License code About Email Install Figure 2 The VehicleCounter License page 2 Installation To install VehicleCounter on an ACAP enabled Axis camera it is first needed to obtain the application EAP package provided by Magenta srl If you do not have one you can request it by writing an email to magenta magentalab it or visiting http www magentalab it page id 189 Then follow these steps 1 access the camera server web interface and browse to the Application Packages page 2 in the section Upload Application choose the EAP pa
23. rn the background signal In this case it can help rising the top threshold since the sensor starts counting when the signal extrated from the pixels minus the background signal falls below the top threshold If this does not work try a different position for the counting sensor 3 I get a lot of busy alarms from a particular sensor What can I do First of all it can be of great help to capture images of the event that caused the alarm to occur For this use the programmable alarm event as described in Section 8 Then it is likely that the pixels observed by that sensor suffer from sudded variations such that the application believes they are due to a vehicle passing onto the sensor Examples of situations that can occasionally cause this behaviours are objects moving in front of the camera partial or total occlusions of the camera unusually sharp edged casted shadows In this cases the user can either a raise the bottom threshold this will make it easier for the sensor to transit from the busy state above the top threshold to the non busy state below the bottom threshold b enlarge the sensor bigger sensors tend to collect smoother and lower signals with respect to small sensors This should make it easier for the sensor to transit from the 14 15 Ei Vehicle Counter Se Mage nta User mannal 4 softwarelab busy state to the non busy state I cannot install the EAP package and or the
24. sor first with respect to che vehicles direction then the second sensor and then to provide a distance in meters This distance is the approximate distance between the points in the real world that correspond to the sensors position on the image This kind of element counts vehicle passing on the second sensor and provides a rough estimate of the vehicles speed by measuring the time that it takes to the vehicle to get from the first to the second sensor e Speed2 Probe This is the most complex probe availble at the moment It provides the same information given by the Speed probe but it is more accurate in both counting and estimating the vehicles speed because it uses three different sensors per element The first and second sensor are used for speed estimation only while the third sensor is used for vehicles counting In this way the two functions are decoupled and the user is set free to dimension the sensor conveniently thick sensors for speed estimation thin sensor for vehicles counting In Figure 4 the preview pane shows a configuration made up of 12 sensors the blue boxes drawn upon the image organized in 2 probes one for each direction of the vehicles Each probe is made up of 2 elements since this is a convenient setup for this particular use case one element for each road lane And since the probes are Speed2 probes their elements are made of 3 sensors each two of them are used to estimate vehicles speed they are na
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