Line-Crossing (Tripwire) vs. Motion Detection?

[Dramus]

The latest release of Synology Surveillance Station now has support for Dahua IVS. Before I go to the trouble of messing with it, is line-crossing any less susceptible than motion detection to "false positives" such as the shadows of trees moving on a sunny, windy day; headlights flashing across an area, lightning during a thunderstorm, etc.?

 

[tigerwillow1]

Line crossing is extremely less susceptible to false positives than motion detection. Easy to set up and well worth it. There are some exception cases where motion detection will be a better choice but they are quite rare IMO.

 

[Dramus]

Thanks, @tigerwillow1. Can you tell me how the rectangle Tripwires behave differently from the lines? (Other than the lines can be drawn diagonally, and the rectangles/boxes cannot.)

 

[biggen]

You can setup intrusion or missing object detection in the boxes. Read up on IVS events from Dahua.

 

[aristobrat]

Thanks, @tigerwillow1. Can you tell me how the rectangle Tripwires behave differently from the lines? (Other than the lines can be drawn diagonally, and the rectangles/boxes cannot.)

One nice thing about drawing an intrusion zone box is that you’ll get options to trigger when an object crosses any of the lines (so it works like tripwire) as well as an option to trigger if any object “appears” with the box.

iMO, tripwires don’t always work great when near the edge of the image. The camera usually needs time to determine if movement is truly an object or not, and sometimes by the time the camera has figured that out, the object has already crossed the tripwire. In that case, the event won’t trigger. If you had drawn an intrusion zone box and had the “appears” option enabled, it would have triggered.

 

[Dramus]

Ah, thanks, @aristobrat. That's especially handy in my case, because some of the Tripwires I want to set up will be near the edges of camera coverage.

@biggen: Maybe my search fu isn't good, lately, but I have been looking up on "Dahua IVS" and the like. The blog posts I've found haven't been terribly helpful--to me, at least.

 

[Dramus]

Hmmm... Can't seem to get an intrusion box configured. I draw it, hit "Save" and it tells me to begin drawing. I come back and the box is a line that isn't even in the same place, but starts in the same place as where I started drawing the box. Can't figure out what I'm doing wrong.

And you're right, @aristobrat: Lines near the edge of the camera's viewing area don't appear to work. At least small ones do not.

 

[biggen]

So when you hit the "+" to add the new rule did you change the dropdown box to "Intrusion"? Then you click "Draw Rule" and start at a corner where you want the box and keep clicking until all 4 corners are where you want them. Then right click anywhere to stop drawing. After the box is drawn, you can hold the left click down inside the box to move the entire box if you didn't draw it exactly where you needed it.

 

[Dramus]

Ah, ok. No, I left it on Tripwire. But then it let me draw boxes, anyway?

 

[biggen]

Well it may let you draw boxes but its not want you want.

 

[Holbs]

I have all my cams set for motion detection. Lots of false positives. Can't blame them since lots of leaves swaying in the wind. I may have to look into the IVS system instead.

 

[biggen]

IVS is great. I use it for snapshots mostly and still have BI doing motion detection separately. I never get false positives with IVS triplines.

 

[Holbs]

It's either looking into IVS, or get my lazy butt out there and put on hold my other 5 simultaneous projects I have going on and do some much needed trimming on overgrown weed trees

 

[biggen]

It's either looking into IVS, or get my lazy butt out there and put on hold my other 5 simultaneous projects I have going on and do some much needed trimming on overgrown weed trees

I mowed the lawn this morning so I know how you feel. 93F degrees here in FL with 60% humidity. Gotta love it!

 

[Dramus]

Yeah, @Holbs, that's one of the problems I have, right now. I think I'm going to have to put IVS off to another day.

Neither the Tripwire I have drawn at the end of the driveway nor the Intrusion box I have up near the upper-right corner of the camera's coverage trigger when I walk through them. I know it does work, both on the camera's and SS' part, because, if I draw a Tripwire or Intrusion zone across the porch and walk through it, it triggers and I get a recording.

I'm beginning to suspect IVS doesn't work on things that are small to the camera, such as a human being walking across a Tripwire a hundred feet away or through an Intrusion zone thirty feet or so off to the side?

I think the Tripwire at the end of the driveway I had defined did trip on my Jeep driving through it, yesterday, but I'm not certain.

 

[biggen]

You have IVS enabled under "Smart Plan" right?

There is a target filter that you may have to play with to get the size right.

 

[Dramus]

You have IVS enabled under "Smart Plan" right?

Thanks for the help.

Yeah. Like I said: I know both Tripwire and Intrusion detection work. I tested them with a line and a box right up near the camera, which is over and off to the side of the front porch.

There is a target filter that you may have to play with to get the size right.

I had thought that might be the case, but it's unclear to me what to do with that. The default is a Max Size of 8192 * 8192, which is bigger than the size of the camera (2MP). Min size is unchecked and appears to be a default of zero.

And what's with the Draw Target, Clear, and Draw Target buttons to the left of those size boxes?

Is there any actual, you know, Documentation, readable documentation, for these features anywhere?

 

[biggen]

There is the Dahua Wiki on IVS features.

First "Draw Target" is for the Max size. Clear clears out what you've drawn. Second "Draw Target" is for the Min size. You have to actually hit the "+" button to add a rule then adjust the dropdown to the event you want to use before using the drawing tool.

Honestly it just trial and error as far as figuring it out.

 

[Dramus]

That's what I thought. Ok, thanks. I'll just leave this for another day. Thanks again for your help.

 

[Dramus]

So far I'm finding line-crossing (tripwire) and intrusion detection only mildly more useful than motion detection, and even then only in certain, very limited circumstances. Lights coming on, headlights flashing across the lawn, shadows from trees blowing in the wind--all of these "false" line-crossing every bit as badly as they do motion detection.

I think, ultimately, if I want cameras that are going to alert me to actual potential intrusions, rather than bugs, lights, headlights, shadows, clouds, and lightning, I'm going to have to toss these Dahua cameras for something with IR motion detection. Video motion detection may be fine for indoors, but it's pretty much worthless outdoors, IMO.

Wish I'd known that, or at least thought of it, before investing $600-$700 in cameras Oh well, live and learn.