IVS Global Calibration - Detailed Questions

[Kevin Doe]

I've got IVS rules working pretty well, but they miss the target at times. I have not yet done the global calibration on the camera, and have a few questions pertaining to the procedure.

Resources:
1. DahuaWiki
2. Youtube video from Dahua



Questions:
1. How do I determine what to include in the calibration area? Should this only be set to include the IVS detection areas in the rules that I set? For example, should the area encompass tripwires and intrusion areas and nothing else? Why not include the entire image?
2. For the three vertical rulers, is there any sort of guidelines about how they should be placed? I was thinking you'd want to space them like this: One in the lower 3rd of the image, one in the middle 3rd, and one in the upper third. My thinking is that as you go from the lower third toward the upper third, the aspect ratio of the image causes the ruler to shrink in size. Sort of like picturing a person standing on train tracks that travel away from you. The person appears smaller as they are further away (higher in the image area).
3. For the horizontal rules, it seems like it will matter where you place it (vertically in the image). Should it be placed near any of the three vertical ones?
4. For the calibration validation, they show measuring one of the yardsticks that you included in the calibration. Wouldn't it be more useful to move the yardsticks to locations between and see if the calibration worked, such that lengths can be estimated away from the locations that were calibrated. Seems like not much of a test, to check the area right near the calibration.

Not knowing how the algorithms work, I'm not sure what the intention is as far as placing these calibrated measurements. Can anyone shed some light on this?

Let's use this image as an example. I was thinking I'd place the vertical rulers, one in the middle of the seating area, one mid yard, and one near the shed. Horizontal one, no idea. Thinking calibration area would be my property limits, which matches my night time IVS rules.

 

[wittaj]

How I have done it in relation to your questions:

Questions:
1. How do I determine what to include in the calibration area? Should this only be set to include the IVS detection areas in the rules that I set? For example, should the area encompass tripwires and intrusion areas and nothing else? Why not include the entire image? I have done it for the entire area - the AI in the camera works best when it has time to identify the object and run it through its algorithm, so I want it to be able to start seeing the object outside of the IVS zones.
2. For the three vertical rulers, is there any sort of guidelines about how they should be placed? I was thinking you'd want to space them like this: One in the lower 3rd of the image, one in the middle 3rd, and one in the upper third. My thinking is that as you go from the lower third toward the upper third, the aspect ratio of the image causes the ruler to shrink in size. Sort of like picturing a person standing on train tracks that travel away from you. The person appears smaller as they are further away (higher in the image area). I have done it in a similar fashion.
3. For the horizontal rules, it seems like it will matter where you place it (vertically in the image). Should it be placed near any of the three vertical ones? I have not placed in near the 3 and instead tried to get it in a blank area of where the 3 were.
4. For the calibration validation, they show measuring one of the yardsticks that you included in the calibration. Wouldn't it be more useful to move the yardsticks to locations between and see if the calibration worked, such that lengths can be estimated away from the locations that were calibrated. Seems like not much of a test, to check the area right near the calibration. It has been awhile since I last calibrated a camera, but I think you can check each one and zoom in to get it more accurate. I haven't calibrated my 4K yet as it has been spot on in my field of view.

I think your idea of where to do the 3 vertical is fairly spot on. I wouldn't make it a straight line though between the three and instead offset them a bit.

And then test and rerun the calibration in different areas if it is still missing.

 

[Kevin Doe]

I have all 4 "rulers" out there. I just happened to have some metal poles that were exactly 1m laying around, so that worked out well. You can see where I have the three verticals, and one horizontal. I saved the configuration. Then click on width verification, and "calibration valid..." and it asks me to draw a line. I do, but it doesn't show me the measurement like the Dahua instructions and video shows. Any ideas?

 

[Kevin Doe]

I ended up trying the calibration validation steps in Chrome, and when I drew the lines, I actually got a measurement value to show up on the screen. Only problem is that the on-screen measured distances, both height and width, didn't match the physical 1-meter poles I have in the ground. I suspect it has something to do with where I placed the three vertical poles relative to each other, and within the frame.

I found this guidance in the Dauha Wiki, although I'm not sure what it actually means: "Select three reference objects with fixed height that are positioned in a triangular distribution".



Should the three reference objects be like this? (Tried this, didn't seem to work properly when I checked the calibration validation)



Or this:

 

[Mike A.]

I'd think the latter.

Maybe a better way for them to have said it is to arrange in a linear way so that the distance/calibration can be triangulated based on the known height.

If that makes sense.

 

[SpacemanSpiff]

Ever calibrate a touch screen? If its a 14" square area, and you use only 3 points of calibration within a 6 sq inch column area, the accuracy will be... not so good. A touch screen is only 2-D (X & Y axis'), however IVS global calibration is a 3-D area (X, Y & Z). I believe you'll provide the system a more accurate depiction if you have the 3 verticals spread out more around in the calibration area.

Based on the second image... keep the 1st stick on the patio area, place the 2nd stick off to the left half-way between the sapling and the shed, and the third? Consider marking 1 meter (not 1 yard) on the first tree to the right of the shed up on the hill.

 

[handinpalm]

Unfortunately, the basic understanding of Dahua algorithms for IVS are not known by anyone except the Chinese software guy sitting in a dark hole somewhere. Dahua needs to make more algorithm info available for the user, instead of everyone guessing what is best way to setup their camera. It is all hit and miss until you stumble across something that works reasonably well. Hopefully they will smarten up and educate the end users. Maybe Andy ( @EMPIRETECANDY ) can provide them with some feedback from the users/installers.

 

[sebastiantombs]

Don't use Chrome, use Internet Explorer, specifically. IE is still available in Win10, just type "explorer" (no quotes of course) in the search bar, point and click. Dahua cameras are sensitive to what browser is used and even other browsers with IE extensions do not work well with them.

 

[Kevin Doe]

Don't use Chrome, use Internet Explorer, specifically. IE is still available in Win10, just type "explorer" (no quotes of course) in the search bar, point and click. Dahua cameras are sensitive to what browser is used and even other browsers with IE extensions do not work well with them.

I use exclusively IE for the camera stuff. I did the calibration in IE, but when I got to the calibration verification steps, the length of the line was not displaying. So I tried just the calibration verification step in Chrome, and the length of the line displayed on the screen. Not sure what else to do.

 

[wittaj]

Were you using IE through the NVR GUI interface or did you pull the camera off the NVR and connect to IE as a stand alone browser?

 

[Kevin Doe]

Were you using IE through the NVR GUI interface or did you pull the camera off the NVR and connect to IE as a stand alone browser?

I use the NVRs IP to access the NVR. Then settings, camera, to see the camera list. Then click the IE button. I haven't unplugged the camera and tried to connect directly to it. I don't actually know how to do that.