Hello folks,
I'm setting a goal for myself to build a device that will point a small antenna to a known GPS location (lat,long,alt)
My antenna will never be more than 12 miles from the known GPS location.
I will need to move my antenna project every couple of months within my 12 mile radius but it will always point back to my known gps location.
Regarding hardware,
I believe I will need:
arduino (which one not a clue) GPS shield (recommendations appreciated )and two servos.
Possibly an electronic compass.
This will be my first arduino project
If you could provide any direction it would be greatly appreciated.
I don't believe you will need a compass. An on-board GPS is there to determine one position and a the other position is static by definition. You can therefore calculate altitude and azimuth for the antenna, and I guess the GPS can do that chore for you.
This is the sort of project that radio hams do. You could try looking at some web sites for built examples of this.
You would not use a servo and controlling tha azimuth is unnecessary.
Nick_Pyner:
I don't believe you will need a compass. An on-board GPS is there to determine one position and a the other position is static by definition. You can therefore calculate altitude and azimuth for the antenna, and I guess the GPS can do that chore for you.
But the device does not know its own orientation just from the GPS location.
It seems to me that a simple map and compass with manual orientation would be much simpler, more portable, sturdier and faster. Once in a few months is really not that often for such a simple operation.
Other than that, Grumpy's suggestion of radio beacon seems a lot easier (think low power NDB).
How accurate your antenna pointing has to be?
What kind of terrain is in your 12 mile radius (hills, plains, urban, rural etc)?
Will you be positioning your antenna somewhere in the wilderness, out in the open or in a building?
How?
A GPS only returns lat and long. You can only get a heading if you are moving. When you are static ther is no way of telling where you are pointing.
With all respect, oh great one, oh, yes they do. You get a reasonablly accurate 'course direction', with respect to either magnetic, or true, north after warmup and reception of three or more satalites. With earlier modules, your direction got better with movement. But now days, with the multiple channels, you are pretty good from the get go (at least here in the states).
So if you sit a GPS receiver on a table in your garden and rotate the receiver about its own centre it will be able to tell you which new direction it is pointing?
This site has a formula for the bearing which is basically all you need: http://www.movable-type.co.uk/scripts/latlong.html
It gives the general formula for the bearing from one lat/long to another. In your case, if the second one is always the same, the formula simplifies a bit.
But if you only move the antenna once every few months you could easily do the computation of the bearing on a calculator (or Excel spreadsheet), point the antenna and you're done.
123Splat:
Mine do, with better response than my E-Trek handhelds.
I suspect that this is due to the manufacturer adding in an analog or digital compass, NOT because GPS tech got better. GPS only gives you a single point, it has no idea of direction until you move. Even then, GPS accuracy can be all over the place depending on cloud or tree cover.
With all respect, oh great one, oh, yes they do. You get a reasonablly accurate 'course direction', with respect to either magnetic, or true, north after warmup and reception of three or more satalites.
Wrong!
The GPS knows the course if it is moving. If it isn't moving, it doesn't know. Some units immediately revert to a course of 0, some hold their last estimate of the course.
If you want to know orientation when stationary, you need a compass.
Awsome, This forum is a near perfect script of my internal dialog before adding "compass" to my initial post.
I think it's safe to say that a gps with an integrated gps would definitely work for my project (Any suggestions folks?)
I'll try to clarify the specifics.
I'd like the device to be as "hands off" as possible. Once I've plugged in a lat/long/alt I want to turn on the device, have it initialize to the gps sattelites and then point to my predesignated location.
My device will need to host a receiving and transmitting antenna (approximate 2 pounds), the terrain is mostly flat but it will be mounted on 30' tower in the wilderness with trees that are less than 20' tall. The static location antenna has a projection width of 60 degrees. The mobile arduino antenna pointer has a 8 degree beam.
I'm assuming that if I can get the device to point to all three points..lat/long/alt then I will have better signal strength then lat/long alone.
I'm positive there are easier ways to point one antenna to another by ones self, but I've always had a passive interest in robotics and have finally found a project that would help me accomplish what is currently an exhaustive task autonomously. Furthermore, I've 2 young children who I suspect will benefit from having a dad that can help out with electronics projects down the road.
I don't think a GPS, and a compass will be very accurate. If your beam is 8 degrees, you want to point it pretty accurately. To increase your accuracy, you can check the signal received, and make fine adjustments of your beam at the highest signal strength.