Distance and direction

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Spasm

New Member
Hi.

I would like to know how is it possible to calculate distance between 2 points(and if possible the direction of one point to another) using 68hc11 microcontroller and radio transceivers. Should there be a program to calculate or does it need external hardware?

Thanx

Nostrafus

New Member
hmmm... not sure on this one, but depending on how accurate you want your rangefinder to be, I'd probably go with laser, it's extremely accurate, and versitile, used by surveyors to detect all kinds of stuff.

Spasm

New Member
Hi.

Accuracy is not a concern. Just roughly an idea of the location. I would like to use the RF transceivers instead because I've bought it for quite a sum. I'm not sure whether it can be done using radio waves since its propagated in all direction.
Anyone with ideas?

Thanx

Squintz

New Member
i might be wrong but if you transmited a signal to a transceiver and repeated that back to its original transceiver you could calculate how long it took from the time you transmitted it to the time you received it back and calculate the distance based on the speed of radio waves.

i hope i dont mislead you to think i know what im talking about because i dont. its only a concept.

ivancho

New Member
That is not a bad idea.... have one transmiter send one signal "START" then start a timer, and listen for a reply. As soon as the reply is back get the timer information and calculate the distance.

How fast does RF travel on the air? Is it the same as sound?....

Squintz

New Member
you still have the problem of direction an you have the problem of obsticals. I would say use GPS. You can transmit the location of the one Transceiver and use the location of the other and subtract the two to get distance and direction and if you wanted to go further you could check for altitude and speed. all kinds of coll stuff. I love GPS

ivancho

New Member
:!: I believe that seeing how long the receiver transmits back still a problem, because of the wave speed. Since Radio Waves travel a nearly the speed of light and you are not too far away from each other it would be tough to get a time on something that fast. Radio waves travel so much faster than sound waves that a broadcast voice can be heard sooner 18,000 km away than in the back of the room in which it originated.

A signal sent to the moon does not return until 2.7 seconds have elapsed and the moon is approximately 250,000 miles away. That is 1 mile in 10.8usec. :shock:

There must be another way :twisted:

How about something like transmiting the current position read from a digital compass? Since you know your possition then you could get the distance and direction. GPS is another "more expenive", more accurate, and outdoor way of doing it as well

Ivancho

Spasm

New Member
Hey all...

Yeah...its kinda impossible to detect the transmission delay of a microwave even though the microP works in the "micro" time unit. Think delay only works in sound waves rite?
Well squintz....not sure how to access GPS systems..does it involve expensive hardware and subsription?

Any other way? :roll:

Thanx

Squintz

New Member
Thanx for all that good information. GPS Receivers a fairly cheep and they output rs232 which means a microcontrol would be able to handle all the processing needed. And for the task at hand it could give you that and more.

I wish someone would do a tutorial on this site about GPS and their outputs. I beleive the format they output is know as NMEA often pronounce (knee-ma). NMEA is an orginization the provides standards to marine equipment. Hince the name National Marine Electronics Association

The GPS Protocol provides:

$GPGGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh GGA = Global Positioning System Fix Data 1 = UTC of Position 2 = Latitude 3 = N or S 4 = Longitude 5 = E or W 6 = GPS quality indicator (0=invalid; 1=GPS fix; 2=Diff. GPS fix) 7 = Number of satellites in use [not those in view] 8 = Horizontal dilution of position 9 = Antenna altitude above/below mean sea level (geoid) 10 = Meters (Antenna height unit) 11 = Geoidal separation (Diff. between WGS-84 earth ellipsoid and mean sea level. -=geoid is below WGS-84 ellipsoid) 12 = Meters (Units of geoidal separation) 13 = Age in seconds since last update from diff. reference station 14 = Diff. reference station ID# 15 = Checksum http://www.kh-gps.de/nmea-faq.htm Spasm New Member Hi. Well, this means the GPS receivers will be used instead of RF tranceivers to calculate the distance. Hrmm...this is kinda off the scope since I would prefer not to waste the RF tranceivers. Is there another solution? Thanx Squintz New Member the gps receiver is that only... It does not transmit nore does it calculate anything for you. It simply receives a signal from more than one satalite. it need atleast 3 to work but i think it uses 7 or so at one time. You would still need to transmit via RF the data received from the GPS Spasm New Member Hi. I think the GPS receivers cost$100. Thats pretty expensive.
Is there a cheaper solution to this?

Thanx

Brocktune

New Member
You would just have to research how RF locators work: the ones used to locate animals after you put a radio collar on them. You know, you can see people using them on the discovery channel when they are tracking down animals.

I don't know how they work, but I would imagine there is some pretty sensitive analog electronics (oscillators, phase-locked loops, etc.) that you can use to do the math that calculates how far away a signal is. Then you can pump the analog signals into the 68hc11 (they have an a/d right?) and write some assembly code that will do range calculations.

Noggin

Member
If you can put down three tranmitters and then detect signal strength, then you should be able to do a bit of math to triangulate the position. If you know the location of the three stationary devices, then you should be able to map out your receivers location.

Someone Electro

New Member

By the way electricity travels 100 000 km/s dose the radio waves travel that fast to?

O and geodesists have some instruments to send some light and its reflected by a miror and then it shows the distance centimeter precise!

Sebi

Active Member
You can determine the position of transmitter with two (or more) receiver.This is a classical method with directional aerials (loop or Yagi): rotate the aerial to maximum TX signal, draw this direction as a line on map. Repeat it on another point, draw the line, and the crosspoint say the TX position.
The "foxhunting" sport: search for TX with one RX and Yagi antenne. In this case the field strength meter also give good information about distance. This method can see on Discovery Channel.

Spasm

New Member
Hi all,

Hrmm...sebi..this means it will need at least 2 receivers to pin point the location rite? Is it possible to use one?
Someone electro....radio waves are microwaves...therefore, speed of light..I think the only Tx/Rx that can detect using delay transmission are the ones with atomic clock processors ( piko i think ). The microP only in microS....
Okay...so there is 2 way now...GPS and the triangular format...
Any other extra ways?

Thanx

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