LPR Feasibility

RBN

n3wb
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I’ve had a surveillance system for a few years now and have good coverage of my property, but I intentionally aimed them to minimize overlap into adjacent properties as I didn’t want to intrude into their privacy. A neighbour was robbed a couple weeks back, however, and that’s made me reconsider some of those decisions after talking with him and the others around me. We did get clear shots of the side of the bad guy’s truck when it drove past my house and turned into his driveway, which gave police a timeline as well as make/model/year/trim but no licence plates or faces as the video was perpendicular to his travel. I was able to look back on the footage and find what appeared to be the same vehicle casing the place out a few days before, but again no plates and it was a royal pain to manually pour through all that footage.

I’m flirting with adding another camera shooting up or down the road to try and get the front/back of passing cars for some identifying information should something like this happen again. Ideally I’d like to run some sort of ALPR software to be able to search for that quickly, but for the time being I’d be happy to just have something that would capture close-up photos I could cross reference against the wide-angle view of the road I already have. In this case the Police were at my door asking for access to the footage within 20 minutes of the burglars leaving, so even if the truck was stolen it’s possible a licence plate may have been enough for them to catch them.

The tricky thing is that my house is set back about 65’ with a bunch of trees in the front yard to work around, so I’ve got a few questions before I go out and buy a camera and start fiddling around with this:
  • How important is it to get the angle down to 30 degrees or less vs the other tradeoffs? If I point the camera east I can position it to look right underneath a street light just past a stop sign (ie very well lit and cars will be moving slowly due to the intersection), but because of obstructions the best I could get would be about 42 degrees. If I point it west I can get the angle down to 25 degrees but it’s mid-block (ie they’ll be moving at full speed) and pretty dark. The former position would be about 100’ and the latter around 140’. Speed limit is 40km/h (~25mph) which is about what people travel at (there’s lots of intersections so not much time to accelerate before they have to stop again).
  • How critical is the vertical angle to making plates identifiable? All of the above is because I’m trying to keep it just above the ground level windows, but if I went up to the second floor I could shoot over most of the obstructions and look further down the road (reducing the horizontal angle and better utilizing the street lights and stop signs). It’d be more of a pain to install up there and while I’d normally write that off as a one-time annoyance, it looks like there’s a lot of fine tuning involved in this application so I might have to go up there a lot.
  • I’m looking at the Dahua Z12 cameras given everything I’ve read here; how sensitive are these in low light? I’ve got a 400mm lens for my DSLR that roughly correlates to the 5 degree FoV these have fully zoomed in which I can use to test angles, but I’m not sure how to simulate the exposure to figure out what I’d be looking at to get the appropriate shutter speeds. The minimum illumination spec is listed in the context of 30IRE, but if I understand it right that wouldn’t yield a particularly useful image - if you guys know the minimum lux you’d judge as usable I can calculate the corresponding EV and work from there? Naturally I’d likely be using IR at night, but I’d like to get an idea of what that street light could do.
  • Are there any ALPR software packages that can be purchased outright? OpenALPR looks great, but it’s utility is not worth $50/mo for my limited uses - I don’t mind paying for something, but I’d strongly prefer something with a perpetual licence. The free tier would work, but with only two days of retention I’m not sure it’s worth the trouble vs just manually reviewing footage. The only time I see myself looking at the database would be if something happened and I wanted to quickly check if that car had been here before (to then check the other videos and see what they were doing).
  • Unrelated to LPR, but as I’m here anyway - when they broke into my neighbour’s place they disabled his security system and dug through his wiring closet likely looking for surveillance recorders. Naturally, all the cameras in the world will do no good if they make off with the recordings - do you guys do anything to protect against that scenario? I’ve hidden my DVRs, but there’s a whole gaggle of wires converging on that point so if someone knew what they were doing they could probably find it. Streaming terabytes of video off site seems like expensive overkill - maybe set up a computer somewhere else in the house and pull video from the DVRs to store a second copy?
 

Will.I.Am

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In regards to your last question - most ip cameras can be set up to record directly to either an sd card or network storage.

I always like to have the cameras record to a separate nas, on top of the normal nvr recordings, but only on motion or alarm.

Another step could be to have your switch gear in a different location to your nvr so they can't just follow the cables, then have the nas in a different location again.
They can still steal the lot, but the more layers there are, the more time it will take.

And in an area where you have neighbours, a good, well installed and maintained intruder alarm that is set every time the house is empty makes sure they don't have as much time as they'd like before the alarm is raised. Imo, cctv is worthless if you don't have a working intruder alarm as they have potentially hours to find your nvr.


As for covering only your own property, I'm not sure about elsewhere, but in the UK it's perfectly fine to cover a reasonable public area around your home as long as you display signage and you aren't looking in to anyone else's house or private land without their authorisation. That's what privacy masks are for.
 

RBN

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Another step could be to have your switch gear in a different location to your nvr so they can't just follow the cables, then have the nas in a different location again.
They can still steal the lot, but the more layers there are, the more time it will take.
Good point - right now everything goes to my DVR, but I could get a PoE switch and relocate the recorder somewhere else. One of the DVRs uses coax so I couldn’t do much for it, but it’s just a gap filler so it’s not critical (and could be a benefit as they may assume they got it all after taking it out). Never checked the PoE cameras for SD slots, but I’ll definitely climb up and check them.

And in an area where you have neighbours, a good, well installed and maintained intruder alarm that is set every time the house is empty makes sure they don't have as much time as they'd like before the alarm is raised. Imo, cctv is worthless if you don't have a working intruder alarm as they have potentially hours to find your nvr.
They (like us) had a monitored system, but the intruders kicked down the front door and disabled it (threw the main breaker then pulled the battery out) before the timeout for keying in the code expired. I would have expected the system to call the monitoring station right away and simply not raise an alarm if the code was successfully entered, but apparently their system didn’t do anything until the full alarm sounds. Even so, they were in and out in 13 minutes though so your point is good that even a little obfuscation would probably be enough (in his case the main network switch and security system were right beside the electrical box so it was easy pickings).

As for covering only your own property, I'm not sure about elsewhere, but in the UK it's perfectly fine to cover a reasonable public area around your home as long as you display signage and you aren't looking in to anyone else's house or private land without their authorisation. That's what privacy masks are for.
Wasn’t too worried about the legality, more about figuring it’d be creepy to have videos of all their comings and goings. One of my cameras unavoidably gets their front yard from the side in the background, but I carefully set the motion detection on it to not trigger past my property line - in hindsight that was foolish as it would have gotten nice clean video of them breaking in if it was recording. He’s getting a system put in now and I made it clear he’s welcome to overshoot all he wants onto my lot as that’s the best redundancy I could ask for - I’ve also sat down with him and the other neighbours and changed the motion settings on a few cameras to their liking.

In retrospect I think the key lesson is to talk this stuff over with neighbours and coordinate the systems as best you can - we’re all on good terms and I was worried about things they had no issue with. It’s not like a police CCTV system that’s constantly being watched - the only time these home systems are reviewed is when something goes wrong.

Thanks for the quick and thorough response!
 

bigredfish

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I'll take a stab at some of those: worth what ya pay for it.

1- Angle is important. I have one at 30+ degrees and 16ft above the roadway @120ft and its tricky. More than 30 gets even harder. With the Z12 once you get past 140ft it gets iffy as to holding focus, unless your shooting dead straight on and dont really have to use as much zoom, but then you'd probably be capturing at something less.

2- Same but second floor should be about the same as my pole mount at 16ft

3- You;ll probably need IR at night unless you have a hell of a lot of white light at the capture point. I have one 20ft away from a street light and still use IR. Typically exposure is going to be in the 1/1000- 1/2000 range.

4- Like you I have overview cameras to synchronize events if I need, its not like I need a database of plates or am going to be pulling multiples per day. After the novelty wore off I learned that it will be there and easy to grab if I need it. (* Caveat being I'm fine with 10-14 days recording. If it happened before that I probably dont care anymore)

5- Mine isnt that hard to find, but my house alarm would let me know if a sensor is tripped and/or if power is cut. And I would have already seen an email and maybe push notification from one of the cameras before they got in.


Here's a 5231VF Starlight standard bullet working Overview right beside a Z12, capture point is 120ft
(change youtube player to 1080p)

 

Will.I.Am

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Good point - right now everything goes to my DVR, but I could get a PoE switch and relocate the recorder somewhere else. One of the DVRs uses coax so I couldn’t do much for it, but it’s just a gap filler so it’s not critical (and could be a benefit as they may assume they got it all after taking it out). Never checked the PoE cameras for SD slots, but I’ll definitely climb up and check them.
Loads of hik and Dahua cameras have the slot. a 64gb sd recording on motion only will give you months in most domestic uses.


They (like us) had a monitored system, but the intruders kicked down the front door and disabled it (threw the main breaker then pulled the battery out) before the timeout for keying in the code expired. I would have expected the system to call the monitoring station right away and simply not raise an alarm if the code was successfully entered, but apparently their system didn’t do anything until the full alarm sounds. Even so, they were in and out in 13 minutes though so your point is good that even a little obfuscation would probably be enough (in his case the main network switch and security system were right beside the electrical box so it was easy pickings).
That's why I specified well installed. I install alarms for a living but they have to be done properly, the panel should have tampered immediately upon the lid being removed. When the system was set, this should have raised an alarm straight away.
The external bell should have sounded as soon as the panel was powered down. More to the point, they shouldn't have been able to get to the panel location without triggering a non entry route pir = immediate alarm.
Even my house (which was pre installed with an intruder) had an awful system. No door contacts, no pir covering the panel.
Again, the best place for the panel is well out of the way in the roof space. A smart intruder will try to cut the phone line first but at the very least it'll sound the external bell.

Wasn’t too worried about the legality, more about figuring it’d be creepy to have videos of all their comings and goings. One of my cameras unavoidably gets their front yard from the side in the background, but I carefully set the motion detection on it to not trigger past my property line - in hindsight that was foolish as it would have gotten nice clean video of them breaking in if it was recording. He’s getting a system put in now and I made it clear he’s welcome to overshoot all he wants onto my lot as that’s the best redundancy I could ask for - I’ve also sat down with him and the other neighbours and changed the motion settings on a few cameras to their liking.



In retrospect I think the key lesson is to talk this stuff over with neighbours and coordinate the systems as best you can - we’re all on good terms and I was worried about things they had no issue with. It’s not like a police CCTV system that’s constantly being watched - the only time these home systems are reviewed is when something goes wrong.

Thanks for the quick and thorough response!
If everyone is in agreement, overlapping cameras is an ideal setup - a burglar can't rob every house in the neighbourhood. Ultimately, a well prepared burglar can circumvent most security pretty easily apart from a well installed, hidden, dual communication path intruder alarm, but even that can't stop them breaking in, it can only hurry them up. All we can do is place hurdles in their way.
 

RBN

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I'll take a stab at some of those: worth what ya pay for it.
Much appreciated! Hard to come at problems like this from a purely theoretical point of view, so definitely can use any experience that I can get!

1- Angle is important. I have one at 30+ degrees and 16ft above the roadway @120ft and its tricky. More than 30 gets even harder. With the Z12 once you get past 140ft it gets iffy as to holding focus, unless your shooting dead straight on and dont really have to use as much zoom, but then you'd probably be capturing at something less.

2- Same but second floor should be about the same as my pole mount at 16ft
Makes it tricky as I’ve got no structures closer than 65’ from the road to mount a camera on, so geometry is my enemy here - to get smaller angles I need to aim the cameras further away. Would the bigger PTZ cameras help with the focus issues at longer ranges? I was looking at the Z12 because I didn’t see a need to move it once it was set up, but they’ve got even narrower FoV so perhaps their optics are better suited to the task.

I could potentially build pillars at the end of the driveway to house them, but (a) that’s a much bigger/more expensive proposition and (b) they’d have to be relatively low to the ground so I’d be worried about snow banks getting in the way during the winter.

3- You;ll probably need IR at night unless you have a hell of a lot of white light at the capture point. I have one 20ft away from a street light and still use IR. Typically exposure is going to be in the 1/1000- 1/2000 range.
Okay, that actually makes things a bit easier as I can probably ignore the street lights then. I’ll measure the light levels tonight to be sure, but they’re just standard sodium vapour lamps so not super bright. Given your sample video it looks like 25mph shouldn’t be an issue either, so the west angle might work best - just the longer range that’s the problem there.

4- Like you I have overview cameras to synchronize events if I need, its not like I need a database of plates or am going to be pulling multiples per day. After the novelty wore off I learned that it will be there and easy to grab if I need it. (* Caveat being I'm fine with 10-14 days recording. If it happened before that I probably dont care anymore)
Yeah, I imagine a week’s footage is likely enough for that camera - in my case they came by about four days earlier, and I don’t imagine they’d be thinking much further ahead than that. Main attraction to an ALPR is that it’d make it less labour intensive to find that footage, but given this doesn’t happen often the time spent setting up software like this may be more than it saves in the long run.

5- Mine isnt that hard to find, but my house alarm would let me know if a sensor is tripped and/or if power is cut. And I would have already seen an email and maybe push notification from one of the cameras before they got in.
True, just have us all paranoid after something like this. Good in that it makes you think through weaknesses in the system, but bad in that it makes you fret about edge cases that likely will never happen.
 

bigredfish

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Yep I was In your shoes back in 2012 which made me Dive in. Layers is the best bet, inexpensive perimeter alarms (Guardline) overlapping cameras, good home alarm system and all the usual stuff like locking car doors and having good nosy neighbors!

Ever consider a birdhouse?
 

RBN

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True, it was an old system probably installed when the house was new (~25 years) - when we looked at it afterwards it was just a set of EEPROMs and Relays without an IC in sight. Fortunately we tested ours afterwards and it worked as you said - as soon as we got close to a motion sensor (you’d have to pass at least three of them to get to the box) the full system went off. Definitely going to dig up a service manual to get a better idea of how it works though - it’s always just worked so we never really gave it a second thought before.

The police figured they likely didn’t go for the phone line on the side of his house because I have a couple of visible cameras in the area which may have scared them off. Those cameras have about a month of retention and no one approached it during that period (it wasn’t in a motion zone (it is now), but unless they traipsed through their garden you’d have to pass through one to get to it).
 

RBN

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Ever consider a birdhouse?
Have a couple in the backyard, but none in the front - would certainly make it easier to mount them higher up than pedestals without looking odd. Trenching the wire is the only tricky part as it’d have to pass through some mature gardens (and their tangle of roots) to get to the house.
 
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