PPF - Horizontal Vs Vertical?

I am using the Ip Design Tool to virtualise the PPF and I noticed thier default is pixel/ft (vertical). All the articles here explaining or using the horizontal pixel counting. If we changed the software default to pixel/m (horizontal), we will get completly different result. This made me wondering, is thier default settings are misleading? or when we could you use VFOV instead of HFOV?


I would avoid using a vertical metric at all.

Since it violates convention (literally everyone else I have seen uses horizontal only), you risk making errors. You will have to adjust what others tell you. Plus, you risk that if you report your specification vertically, they will assume it's horizontal.

Here's an excerpt from JVSG's release notes:

"Pixels per Meter values (horizontal & vertical) are shown ... For example 57 x 43 pix/m means 57 pixels per meter (horizontally) and 43 pixels per meter (vertically)."

Presumably, this is for a 4:3 aspect ratio camera (57 x 43 is 4/3). Also, I suspect that the horizontal vs vertical numbers they report would differ for an HD / 16:9 format.

I am confused overall. I am not sure what this adds, but I am very confident that it will cause even more challenges. In our training courses, one of the most difficult concepts for people to get is PPF. This type of alternative metric only makes it harder.

Background reading: PPF Guide

There is something doesn't add up. The camera settings are the same except I changed the default PPF virtualisation from vertical to horizontal


The UI layout often confuses me. Ethan, though, is a fan and may have suggestions. Also, I will pass this on to JVSG for comment.

My best guess / recollection is that those colors correspond to ppf ranges. If you look at the bottom right side while hovering over those colored areas, I believe it reports details that can help explain it. That said, I am not sure why the colors change or what it is means.

This is the color map; for example, the red for identification and the blue monitoring

I found this in the Help content:

The default settings of the camera zone visualization method in vertical pixels/foot are shown below.

Zone Type

Vertical pixels per foot

Color

Monitoring

10

Light Blue

Detection

20

Light Green

Recognition

40

Yellow

Identification

60

Light Red

Dear Undisclosed Integrator,

Thank you for your posts here.

Your post here helped us to identify a bug that appears on the rare occasion when in Imperial Mode (when all distances are measured in feet) the user chooses Pixel per Meter based camera zone visualization methods, like “Pixels per meter (horizontal) pix/m”.

This error doesn’t affects all other modes. This is why we have not found this bug when we updated H-PPM formulas in version 7.0.0.808 on 1st June 2013.

We will release a fixed version on Monday.

Thanks. Anyhow, the setting was Autodetect. One more thing, why there is horizontal pixel / ft?

Sorry, why there is no horizontal pixel / ft?

Thank you for your suggestion.

We will add Horizonal PPF in the next version.

I have brought this very issue up with JVSG and I pointed it out to Brian many months ago. I thought it must be a typo. I never heard back on it.

We just published the fixed version 7.1 build 870.

"Horizontal PPF" visualization is included in the new version too.

We will notify existing users via automatic software update notifications.

In addition we will send an email newsletter to all registered users in a few days.

Max, thanks for the update. Can you clarify where the vertical PPF feature came from? Is there some country, region or association using vertical? Just curious!

John,

Vertical PPF calculation in regard to image recognition does seem to short supply, but there are several examples like this one, from high-end security firm Cohu (reviewed here).

Excerpted:

Step 1: Calculate Pixels per Foot in Image

Pixels per Foot = Image Resolution / Field of View •

HPF =[1280/259]=5 PixelsperFoot •

VPF =[720/145]=5 PixelsperFoot

Step 2: Calculate Pixels on Object Pixels on Object = Pixels per Foot x Object Size •

HPoT =5 HPF x2ft. =10HPoT •

VPoT =5 VPF x6ft.=30VPoT

HPF = Horizontal Pixels per Foot

VPF = Vertical Pixels per Foot HPoT

They claim that this is based upon pioneering work done by John B. Johnson, however I'm not certain that Johnson actually considered VPF or even pixels at all due to the time frame of his work, i.e. the late fifties.

Might the 'convention' of HPF be an artifact of the scan orientation of an electron gun?

Nonetheless, as you express, I doubt there is any pragmatic value in the advocacy of any convention 'violation', except solely as an intellectual pursuit to understand how and why symmetry is broken between the two orientations, but none that bears application to the canonical IPVM curriculum.

I have installed update. All my resolution zones increased in PPF. I am going to double check the math within the program so I am confident on what PPF is being calculated.

I too wanted to know where vertically oriented PPF came from?? I thought it was truly a typo in the program as I was under the impression PPF was calculated from the pixels on the horizontal axis - worldwide. But we Americans always make the mistake of believing the way we do things is the way things are done everywhere. After living overseas for 10 years I got an earful on that topic! :-)

Correct me if I am wrong but there should be no difference in vertical vs. horizontal PPF. A pixel is a square object. Its height is the same as its width. So 50 PPF vertical is the same as 50 PPF horizontal. The measure itself does not need to be expressed in the horizontal or vertical. I think field of view however does need to be expressed in vertical or horizontal

Sorry Jerry...you are wrong. :) Read the PPF articles on this site. It is not about the pixel itself.

Actually, it's not necessarily wrong. It's just that you can't measure vertical FOV the same as you measure horizontal. Or, more correctly, you can, but it's a meaningless measurement as far as PPF goes, because objects at the top of the FOV vertically are lower PPF than ones at the bottom because they're further away.

However, there's an easy way to prove this. Flip a camera into corridor mode without changing the focal length. Like this example from our Camera Selection Guide:

In that instance, the vertical FOV is much larger, but with the subject at the same distance from the camera, PPF is exactly the same.