Some friends and I have been working on an idea, where we will need to measure the distance of several moving objects.
Imagine af group of hikers on a trip...
All of the hikers wear a device which communicates with the other devices, so it is possible for all the devices to see if one device are falling behind, since the signal will be weaker.
It is the biggest distance between two of the units that all of the units will display.
We have only a little knowledge of programming, so a little (or perhaps even a lot ) of help will probably be needed.
The antenna will be omni-directional, since the hikers doesn't necessarily walk in a linear path, hence it can't be lasers etc.
The signal could also be disturbed be tower antennas such as those for cell phones etc., which we would very much like to avoid interfere with.
We have thought about using some sort of RSSI dBm measurement to measure the distance between the devices, but we would very much like to hear your ideas if you have any
We have attached a presentation, where we describe the function of the devices more thoroughly
Boardburner2:
The only way i see this working is to use GPS for position which is then transmitted to everyone to process.
Smart phone exist apps do this but require internet acess.
Using radio signal strength is a very poor way to measure distance
RDF from fixed stations would probably work but omni antennas do not give the required directional information.
Hi,
btw., thanks for the quick response
The problem with GPS-signals, is that they consume a lot of battery power, which we would very much like to avoid.
Some, including us, doesn't always bring a smartphone on our trips, due to the risk of them breaking, which is why we try to develop this device.
The distance doesn't need to super precise, e.g. a precision of 20cm?, over a maximum distance of 5-8m.
We have read reports using some sort of XBee units or RSSI measurement to estimate a distance of a device indoors, and we hoped this could also be used outside
Mikkel-Kj:
Hi,
btw., thanks for the quick response
The problem with GPS-signals, is that they consume a lot of battery power, which we would very much like to avoid.
Some, including us, doesn't always bring a smartphone on our trips, due to the risk of them breaking, which is why we try to develop this device.
The distance doesn't need to super precise, e.g. a precision of 20cm?, over a maximum distance of 5-8m.
We have read reports using some sort of XBee units or RSSI measurement to estimate a distance of a device indoors, and we hoped this could also be used outside
Now, I like a bit of the old fell running and mountains...carrying a mobile is pretty much a must. If one of your party falls 13miles from the nearest phone box/pub....then it is going to take quite a few hours before the Mountain Rescue and/or Air Ambulance will even know about it...
A power pack for a phone and an App is the way forward with this idea.
Johnny010:
Now, I like a bit of the old fell running and mountains...carrying a mobile is pretty much a must. If one of your party falls 13miles from the nearest phone box/pub....then it is going to take quite a few hours before the Mountain Rescue and/or Air Ambulance will even know about it...
A power pack for a phone and an App is the way forward with this idea.
We do always carry a phone, however, not a smartphone, so we can't develop an app for it.
We would very much like to avoid using smartphones while on trips due to their poor battery life.
And yes, if we chose to bring smartphones with us, we would bring battery banks, however, we would like to avoid needing to do that
Besides from perhaps being a nice tool on our hikes, we try to develop this product because we want to become better at programming and thought this would be a nice start, because we all would like to this idea come true.
Rssi will not give you the accuracy you require its very imprecise.
Time of flight measurement as done by laser measures would work but doing that by radio would me a fearsome challenge , probably requiring 100 GHz radar.If it is possible at all.
I think it is as this is how brimstone missiles work.
With a maximum of 8m, you might be able to make it work with ultrasonics. But you're naive about power. Anything you build will be at least as big as the cell phone you say you can't use, at the very least because of the battery.
But wouldn't ultrasonic units require that the units can send signals directly to each other?
Then, what if a human would stand in between the two units?
Secondly, wouldn't ultrasonic distance measuring be interfered by other sound disturbances, e.g. cars?
I don't know anyone, who have worked with ultrasonic units before.
If we assume it will be as big as a smartphone, we still believe it's a better option, because they will be sturdier and probably have a better battery life.
Please keep in mind that even though many of you suggest just using a smartphone, we would still like to develop this unit, because We believe it's a good idea and a good way to enter the programming community again.
About the battery life, we have thought about, if it is possible to make the units "ping" for data in intervals, e.g. every 5. sec., to obtain a better battery life.
Boardburner 2 previosly mentioned using a GPS-system. This would be a much bigger challenge for us (we assume). If we then chose to use GPS-measuring we could make a bigger device, hence a bigger battery.
However, is it possible to make such a system using Arduino, or would we then be bound to buy a actual outdoor GPS from a store?
Hi,
Everytime GPS is mentioned you say too big etc.
Have you researched the latest GPS, they even have them in phones, I have an old C5 Nokia, very old school, it has a GPS, its dimensions are about 9cm x 4.5cm x 1cm., including battery.
How small do you want it?
How long do you want it to run?
For the accuracy and environment you will need to go GPS and a decent wireless system, transmitting is going to use power too,this maybe why there appears to be no similar product available. The technology is not here YET.
Mikkel-Kj:
We would very much like to avoid using smartphones while on trips due to their poor battery life.
And yes, if we chose to bring smartphones with us, we would bring battery banks, however, we would like to avoid needing to do that
For the accuracy and environment you will need to go GPS and a decent wireless system, transmitting is going to use power too,this maybe why there appears to be no similar product available. The technology is not here YET.
Tom.....
Even with GPS you eill not get accuracy that you want.
There are GPS surveying instruments that work down to CM accuracy but they are not very portable.
) of help will probably be needed.