Need help: want to build a real-time GPS tracker for multiple movers

[Aristos Queue]

I volunteer for Scare For A Cure. As a charity event, we run a huge haunted experience every October, and in April, we turn our 3.5 acres of land into a live-action D&D dungeon crawl. We have hundreds of players come through every Thursday, Friday and Saturday night during these months. To make the experience work, we need to keep the groups from running into each other. This requires massive coordination, with various keywords inserted into scripts so actors can pass messages without cluing in guests, and little hidden LEDs showing when rooms are occupied, when they clear, when storyline needs to be adjusted to get groups to empty a room quickly, etc. It's a real pain and we do occasionally botch (like we did last night with two groups hitting into each other, which tends to break the suspension of disbelief).

 

This would be made a lot easier if our central command and secondary posts could actually watch in real time where each group is located. We recently got a bunch of new computers for these posts, so I started wondering if we could build such an application. So I'm here on LAVA looking for recommendations for hardware and APIs for that hardware.

 

In the subject line, I said "GPS", but I am aware of just how drifty GPS is, particularly when guests are moving from inside to outside of buildings regularly. Since I'm wanting to track room-to-room movement, I probably need something with higher precision. I'm open to technologies that require us to have some sort of base station installed throughout the haunt.

 

The trackers need to be something that our guides could carry on their persons discretely. They need to be waterproof -- not just water resistent. They will be used in an environment where there is frequent rain and even more frequent gore cannon (yes, that means exactly what you think it means).

 

I would want to be able to track up to 20 simultaneous groups. If there was a way to put this information on tablets, we have a bunch of cheap Android tablets that could be carried by admins.

 

If there's an off-the-shelf solution to this problem, I'd like to know about it. If not, I'd like to hear any community ideas for devices they've seen that would serve in this environment. Since we have a central computer, my thought is I could build in LabVIEW gather and correlate the data to draw the map of where every group is located, turn that into a web service, and then use Data Dashboard to push that information out to the tablets.

 

Any ideas?

[ShaunR]

There probably are things off the shelf (maybe look into car fleet trackers). This sounds like a fun project that you should just do because you can, though. Maybe later your charity can sell it to other organisations (paintball?) to raise some funds,

 

If you get the users to use their own phones, you will even get cell location enhancement and cell location when GPS is unavailable. Remember that mobile phones are trracking devices that make telephone calls

 

You could use RFID in addition to GPS. GPS is accurate to a few meters (10?) and RFID is cheap. They would be great for detecting when a room is occupied and by whom if the GPS cannot distinguish. I would even be tempted to make my own RFID senders with an arduino or similar, but it really depends on your time-scale.  How long have you got? Whats the time constraints for this project?

 

I'll give your charity some licences for the Websocket API, gratis, if you want to stream the data via websockets to peoples browsers in their tablets or phones (you only need them for development). Webservices? Data Dashboard? Meh! I thought you wanted real-time   That technology is sooooo 2000

[Yair]

I have no practical experience with something like this (or the relevant background to help), but one thing you might be able to do is place some wi-fi access points around and use an app on the phones to collect and transmit the data. I know that there are some apps which claim to be able to fairly accurately locate base stations (such as this one). I have seen one of them (don't remember which) used once and it seemed to be reasonably accurate in a single room with no obstructions. I have no other data points as to whether these are actually reliable and whether they have APIs, etc.

 

I'm guessing that these use the signal strength to determine the distance (probably assuming no obstructions in the way, although I'm not sure how they would know the signal strength at the source), but I'm not sure how they determine the direction, as at least the one I saw seemed to be able to do it without moving the phone. In any case, you might be able to do this yourself using the phone's API to get the signal strength and then triangulating several base stations to get the position of the phone. I'm assuming the main issues would be walls and electrical systems which would change the signal strength and that you would need enough base stations to cover the entire area properly. Perhaps you can mount them fairly high. The water issue can probably simply be resolved with water-tight covers for the phones.

 

Although it's probably simpler to get the location information as Shaun suggested.

[Gribo]

RTLS systems can be quite expansive, especially with these requirements. I work for a company which makes such systems, indoor/outdoor location, sensors and relay outputs, LCD on the agents, GUI and even a LV API. We have used the system in the past to track workers in a construction site.

You can check us out at http://www.precysetech.com

Another company is Aeroscout, which can use the wifi infrastructure for their active tags access points. Their main market is health care (tracking equipment in a hospital).

[Aristos Queue]

Gribo: Almost all of the RTLS systems I have found online are targeted to medical... and priced accordingly. :-S The fact that your website even mentions other use cases is unusual.

 

... and they are all missing a "Buy Now" button, which I have observed is a very bad sign for cost effectiveness.

Edited October 12, 2014 by Aristos Queue

[Gribo]

They are expansive, however, I can ask regarding some of our older, unsupported products, since your requirements are relatively simple.  

[ShaunR]

Gribo: Almost all of the RTLS systems I have found online are targeted to medical... and priced accordingly. :-S The fact that your website even mentions other use cases is unusual.

 

... and they are all missing a "Buy Now" button, which I have observed is a very bad sign for cost effectiveness.

 

It's unusual for buy now buttons for hardware solutions.

 

Here's one for RFID. Many mobile phones also come with Near Field technologies now, too. It really has to be GPS for long range, though. I think Wifi on a few acres will give huge blind spots (just a gut feeling).

Edited October 12, 2014 by ShaunR

[Aristos Queue]

It really has to be GPS for long range, though. I think Wifi on a few acres will give huge blind spots (just a gut feeling).

I would have thought that you'd have different wi-fi routers and whichever routers it was closest to would tell you the position. How would the distance factor into it? Or are you saying that most of these products rely upon all the tags being attached to a single router point?

[ShaunR]

I would have thought that you'd have different wi-fi routers and whichever routers it was closest to would tell you the position. How would the distance factor into it? Or are you saying that most of these products rely upon all the tags being attached to a single router point?

 

Sure, if you just want to use a router as a proximity device and say they are in the building. If you want to know which room they are in, then use an RFID and send the data via that wifi router. You can have 100 scattered all throughout the building then and know who's in all the rooms. If, on the other hand you want to know which room they are in with Wifi, you need 3 of them o do tiangulation with less accuracy and dead rooms.

 

It depends on granularity required and how much time you want to put in You have 4 technologies which can all interface to each other and can be used to pinpoint people. Combinations of those technologies will give you differing accuracies and capabilities.

 

I'd want to be able to resolve who was talking to who, how many are grouped and where and who's wandered off to where they shouldn't. That's just me though

 

If you want a cheap, cheerful and quick solution, then you could just go for them using their own phones (or let them borrow some). Then you don't need wifi or any fancy hardware (although if you borrowed a USRP from NI, you could set up your own cellphone base-station ). You could then just track them on Google Maps with a bit of PHP and javascript on a webserver. But where's the fun in that?

Edited October 12, 2014 by ShaunR

[Aristos Queue]

All I'm after is x, y coordinates for ~30 moving objects on a plane to within 1 meter resolution. Anything more than that might actually get in the way of the project simply by being more data than is useful at this point.

If you want a cheap, cheerful and quick solution, then you could just go for them using their own phones (or let them borrow some). Then you don't need wifi or any fancy hardware (although if you borrowed a USRP from NI, you could set up your own cellphone base-station ). You could then just track them on Google Maps with a bit of PHP and javascript on a webserver. But where's the fun in that?

Actually, that sounds like about exactly the right amount of "fun" for this project, but I have no idea how I would go about doing any such thing. Are you suggesting loading some sort of app onto their phone that would send location data to a central device?

(And can some phones actually provide that level of precision location? My iPhone certainly cannot  -- if I use any map app while walking, my position on the map is liable to update about once a block in some places.)

Edited October 12, 2014 by Aristos Queue

[ShaunR]

All I'm after is x, y coordinates for ~30 moving objects on a plane to within 1 meter resolution. Anything more than that might actually get in the way of the project simply by being more data than is useful at this point.

Actually, that sounds like about exactly the right amount of "fun" for this project, but I have no idea how I would go about doing any such thing. Are you suggesting loading some sort of app onto their phone that would send location data to a central device?

(And can some phones actually provide that level of precision location? My iPhone certainly cannot  -- if I use any map app while walking, my position on the map is liable to update about once a block in some places.)

 

No. I'm suggesting you just use a normal webserver with PHP (or labview if you really must) and Javascript and the phones browser. (HTML5 geolocation).

 

Thanks to the Russians, we now have much better accuracy if your phone can use GNSS.I guess yours can't

[Aristos Queue]

I don't think that approach would work. No one is going to have their phone out and visiting a web page during the event. I need a device that can figure out its location and transmit it while sitting in someone's pocket. I thought you were proposing some way that I could simply identify all the phones on site and triangulate their positions, but if it requires them to be actively in use, that won't fly. 

 

I think I need to keep investigating some of the custom hardware options. 

[ShaunR]

I don't think that approach would work. No one is going to have their phone out and visiting a web page during the event. I need a device that can figure out its location and transmit it while sitting in someone's pocket. I thought you were proposing some way that I could simply identify all the phones on site and triangulate their positions, but if it requires them to be actively in use, that won't fly. 

 

I think I need to keep investigating some of the custom hardware options. 

 

Well, apart from the phone doesn't need to be out and can be in their pocket (they only have to visit a page once that auto-refreshes and leave the browser open without killing it) then you'll need 3 USRPs to do that passively via their GSM signal (not cheap).  But sure. There's lots of ways from using their phones (which we have covered) , RFID tags, GPS pedometers, Wifi triangulation and a myriad of custom soluyions. I could carry on  for weeks giving solutions with the tech available. It depends on you budget, timescale and amount of effort you want to put in and only you currently know that.

 

I get the feeling, though, that you have been asked to do it as the "tech guy" and gone "sheesh, I hope I don't have to build one"

[Tim_S]

Wow, this sounds like a really awesome event.

 

Curious how long a battery in an active RFID tag would last (all of the passive tags I've seen have range <2"), my google search started coming up with inventory tracking systems and laundry tags (passive with range of ~6').

[Gribo]

It depends on what sort of peripherals and how many events/hour you require. A unit which reports once a day can last years on a single LiSOCl AA battery, on the other side, a smartphone which has its transceiver and CPU always on lasts a day or so.

[Sparc]

Taking a trick from racing events: RFID tags in their shoes and RFID tag scanners on the floor near the doorways of the rooms.  Maybe not.  After checking, the tags are cheap, the readers not so much.  Tags: $1.00.  Readers: $1000.00.  Dropping to a door-acces like reader (which would require the guide to purposely activate) it's about $100 per door.  Of course once you're at purposely activating a push button in each room is simpler.

 

Accelerometers?  Reset at a known position after after each 'lap' of the maze.  A non-trivial amount of DIY involved (microcontroller with WIFI + accelerometer + battery + case + wifi access points) and cost is still about $100 per tracker.

 

Not automatic, but webcams.  Your CIC guys would have to check the webcam feeds to see who is where.

 

Infrared.  Each guide wears an IR beacon and an IR detector in each room can ID the guide.  Smaller hardware requirements than the accelerometer idea.

 

Depending on the Webcam, the IR beacon could assist there too.

 

[Tim_S]

How immune is an IR beacon to rain?

 

Hrm... Sparkfun has a RFID reader board for $25 + the longest range reader (180 mm max) for $35. That could be attached to an arduino with wireless. It's not the sort of thing that will cover a room, but could scan to open a gate.

[ShaunR]

How immune is an IR beacon to rain?

 

Hrm... Sparkfun has a RFID reader board for $25 + the longest range reader (180 mm max) for $35. That could be attached to an arduino with wireless. It's not the sort of thing that will cover a room, but could scan to open a gate.

 

Thinking about it. If you go the micro controller route for the detector, you might as well go for Bluetooth to get the extra range and tell people to keep their ids visible. I once used a similar idea to upload results data to engineers phones when they passed by inspection machines on the factory floor. It continuously scanned for bluetooth phones (not many  tablets in those days ) and if it found one, compared the mac address to a user list. It then pushed the files to their SD card. You may remember the OPP Push software that was in the CR a while ago. That was part of it (the bit that detected and pushed the files). 

Edited October 13, 2014 by ShaunR

[Sparc]

How immune is an IR beacon to rain?

There's an LED submerged in my cat's water fountain.  I had to put the thing together (*some assembly required).  That LED lead is literally two wires and some shrink tube.

 

How immune is an IR beacon to rain?

 

Hrm... Sparkfun has a RFID reader board for $25 + the longest range reader (180 mm max) for $35. That could be attached to an arduino with wireless. It's not the sort of thing that will cover a room, but could scan to open a gate.

$25 + 35 + Audrino ($25) is ~$85 per drop.  180mm is 7 inches (max).  DIY vs. OTS seems like a wash to me.  With OTS winning for the reasons people buy OTS.

[Aristos Queue]

I get the feeling, though, that you have been asked to do it as the "tech guy" and gone "sheesh, I hope I don't have to build one"

That's a good way to summarize it. :-)

[Gary Rubin]

I agree with those proposing some form of RFID.  If you control the environment and can set up your readers wherever you want, I think that's the way to go.

[todd]

Can you count on cell data? Guides can carry Android or iOS phones. BLE beacons can be placed at doorways. Just need a simple change to a proximity app that emails or texts in-proximity beacons to central.

[Jordan Kuehn]

Saw this article and thought of this discussion.  Don't have time to investigate the actual hardware or vendor, but it's an interesting take on bluetooth tracking.