[Animats]

The site is rather vague. They provide the hardware and install it for free, which implies they're selling data to someone else. Who? There's no privacy policy. No terms of service. The "order" button just brings up a blank email.

How does the device tell how many people are present based on counting at a doorframe? Is it counting people passing through the door? Does it detect direction? Is it good enough to estimate the number of people inside by subtracting out counts from in counts? Will this work for wide entrances, such as malls? Is this a passive infrared sensor? Those go blind in hot weather.

This looks like a cheaper alternative to video counting systems, of which there are many. Video systems get about 98% count accuracy. If you already have surveillance cameras, you can often use them for counting. Beyond that, there's queue measurement - not just how many people are in line, but how many gave up and left without buying.[1] (Seven people in a queue is the tipping point – any longer and most shoppers won’t bother joining it. After 9 minutes, shoppers are likely to give up queuing and leave empty handed (other research says as little 6 minutes). 70% of customers who leave never come back.)

[1] http://www.retailsensing.com/queue-management.html

[afar]

[Density founder here] Hey Animats, sorry it took me all day to get to your list of questions.

> which implies they're selling data to someone else. Who?

Typically our customers are startups who sell to SMBs (coffee shops, bars, restaurants, museums, etc). They charge merchants anywhere between $50-$500/mo/location for some kind of software or service. These are startups that sell POS systems, loyalty software, marketing services, discounts, handle logistics, and delivery.

> There's no privacy policy. No terms of service.

Frankly, it should have been there before launch but since people don't "buy" through our website, we decided to sacrifice legal thoroughness for speed to launch. Maybe a misstep but people seemed okay emailing us their request to order.

> How does the device tell how many people are present based on counting at a doorframe?

Two closely situated, parallel infrared distance sensors. We timestamp spikes in voltage as they come in allowing us to see o...1 = entrance. 1...0 = exit. Giving us the current count in a place.

> Is it counting people passing through the door? Direction?

Yes. Not the line outside. Although we can do line detection and estimate wait times. Yes.

> Is it good enough to estimate the number of people inside by subtracting out counts from in counts?

Yes. It's better than just an estimate.

> Will this work for wide entrances, such as malls? Is this a passive infrared sensor?

No. Our current model maxes out at roughly 90in -- that's with two sensors on either side of a double door facing one another. No it's AIR.

> 98% count accuracy ... If you already have surveillance cameras, you can often use them for counting.

You're right. We're just betting that customer-aversion to facial recognition and surveillance cameras is slowing adoption in the long tail of the market we're after - the various independent merchants and sellers that comprise a city and who are too busy making coffee and food to spend too much time on potential controversial technology. See: http://techcrunch.com/2014/05/29/philz-coffee-drops-euclid-a...

[edit: for readability]

[jondubois]

>> Is it good enough to estimate the number of people inside by subtracting out counts from in counts?

> Yes. It's better than just an estimate

What if someone waved their hand in front of it (in a particular direction) in an attempt to subvert it? Couldn't someone trick it into over-reporting or under-reporting the number of people inside?

What if someone is standing idle in front of it (near the door frame) for a few minutes and in the meantime a large number of other people walk in? Will it miss them?

What if two or more people walked in at the same time with no gap between them?

Most importantly: How would the counter ever be able to correct itself from inaccuracies?

[berberous]

Hardware/install is free, but costs you $25/month/location to receive your data. (Not that this means they are not also selling data elsewhere).

[Flammy]

Yup, as soon as I read 'free hardware, free to install' I immediately though 'Service model'

Also I don't think this data is particularly attractive to anyone except competitors... and even then its not like its an email list or anything, merely traffic.

[ihsw]

I would say it's extremely useful -- most establishments have a general idea of foot traffic (ie: POS transactions or qualitative visual assessment) whereas with density.io you have a detailed history of when and where there's foot traffic.

Why would someone want to know this information? Ideas abound! I don't think we've had such easy measurement and monitoring at the fingertips of the general populace.

Having detailed logs of user growth is invaluable (the much-vaunted hockey stick), however this level of granularity is unavailable in the physical world.

Now we can show interested parties that, for example, our storefronts are hockey-sticking, growth is high and projected to grow higher, etc. You get the idea.

[Flammy]

Oh the data itself is interesting, but not particularly sell-able to others, in my opinion.

The alternative to this platform are little devices that monitor things like cellphones that walk into the room, and use this to approximate occupancy.

[x5n1]

It is. If you had a competitor who got most of their business around 8pm on Tuesday. You could offer huge savings at 8pm on Tuesdays driving away traffic from their business.

[tzm]

I own a retail store and have been wanting this type of data to quantify behavior, find correlations and discover patterns. In it's simplest form, it could help to quantify previously 'untrackable' advertising methods.

Other products like this are quite expensive to implement and are geared more towards large scale deployments, not small businesses. I even looked into building my own sensor for this, but I simply don't have time. Happy to see this product emerge.

[kefka]

> The site is rather vague. They provide the hardware and install it for free, which implies they're selling data to someone else. Who? There's no privacy policy. No terms of service. The "order" button just brings up a blank email.

Might I add that if there's no privacy polity, the FTC won't go after you for violating it. And the company is new, so this stuff is "tomorrow" kind of stuff. They have the limelight for right now; might as well use it.

> How does the device tell how many people are present based on counting at a doorframe? Is it counting people passing through the door? Does it detect direction? Is it good enough to estimate the number of people inside by subtracting out counts from in counts?

Doesn't seem so. Looks like they're going for the niche between mom-and-pop to something smaller than Staples.

> Will this work for wide entrances, such as malls? Is this a passive infrared sensor? Those go blind in hot weather.

PIR doesn't die due to hot weather. They go blind in heavy humidity. They start throwing errors and bounces around 40% and up. Here in Indiana, they would be nigh useless right now, unless inside AC.

> This looks like a cheaper alternative to video counting systems, of which there are many. Video systems get about 98% count accuracy.

I'm working on that. I've gotten better than 98% already. My time is "make it better and sell it".

> If you already have surveillance cameras, you can often use them for counting.

That's my point. Most/all businesses already have it. So the whole creep and privacy factor is a moot point. Might as well leverage the tech you already have installed.

[patcheudor]

Also, what kind of battery does it take and how often am I going to need to change it? Honestly, maybe it's because I have too many devices but I'm done with anything which requires a battery swap more than a once every couple years.

[Smushman]

Andrew @ Density.io answered this for me.

The sensor wires in to an electrical outlet. Andrew specified that the wire is custom length; indicating it is manually handled at install.

[noxryan]

I was also wondering about its ability to determine the direction of traffic. If it relies on a location having a separate entrance and exit, that's a pretty big negative. I'm also wondering how it handles large groups. Does anyone have any idea how the hardware works?

[escobar]

There's not much actual information available (this should be concerning), but there have been some clues dropped into past HN threads. This is a picture posted in another HN thread of their "original sensor" which is just 2 basic IR sensors: https://s3.amazonaws.com/screenshots.angel.co/73/340163/7982...

As far as I can tell from the updated website, the new sensor is the same thing, just dressed up nicer. Each sensor is only counting one metric, i.e. ingress. Beyond that, the base hardware (not the sensor) is a Raspberry Pi that connects to both the sensor(s) and WiFi. I'd imagine it would make sense to have many sensors for each box, but maybe not.

[pkelchte]

Hi, that's indeed our old sensor which is composed of two AIR sensors. The new sensor carries a slight upgrade in hardware, but the real power comes from our signal processing. See my reply to thwest here. https://news.ycombinator.com/item?id=9879671

[escobar]

So you use 2 different IR sensors, which "measure your circumference to some degree" and provide a "distance profile" which somehow translates into real-time accurate foot traffic counts. IMO that's definitely a cop-out explanation, and per usual, there is not any actual quantification.

[nemik]

Hmm, look's like Vishay's VCNL3020 in there? Or the good ol' Sharp GP2Y0A21YK0F.

Left wondering why you need a base controller and the dual-PIR's though, especially if the PIR's are connected to DC voltage anyway and not battery-powered like some other commentor said.

I get you would wanna use wifi to talk up to your cloud and maybe that's what the base is for. But seems like a waste if you got something expensive like a Raspberry Pi or other ARM A-series in there. There are much cheaper wifi chipsets out there now these days that could do the same thing without needing all that cost and space of an ARM Cortex A-core, plus wifi, Linux, etc. You could probably get away with putting a small wifi chipset in each of the dual-PIR housings and still come out ahead in cost. The ESP8266 sounds perfect for it actually.

Either way, a pretty cool product.

[HeyLaughingBoy]

Using an Rpi gets you to market much, much faster. Then optimize for cost after it gets popular.

[Smushman]

Andrew @ density.io answered this for me.

It can determine traffic direction; which is a leap beyond current technology i.e. a break beam, which cannot.

[serf]

> It can determine traffic direction; which is a leap beyond current technology i.e. a break beam, which cannot.

all it would take is two or more beams and some pretty simple code, am I missing something?

[escobar]

Nope, not missing anything. There are 2 beams (IR) per one of their "sensors", and it's assumed they're determining direction by noting which beam fires first vs second.