We (Parallax) have had lots of good luck with Garmin eTrex and Geko models. They're easy to connect to, easy to find (even RadioShack has them now), and have a text output mode that is particularly easy for the BASIC Stamp to deal with.
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Dallas, TX· USA
Aren't the GPS sats everywhere?· They move, they're not geo-stationary.· No licensing req'd.· However, the position data is accurate only to one decimal place (the remaining three are garbage,·when your unit isn't·MILitary eqp'd.)
yes, they are not geostationary. they orbit about twice every day. But the last three digits, at least on the garmin etrex, are not garbage. they actually will change accordingly to even a small distance like 5 feet! Also, if those last 3 digits where not acurate, then the hole system would be almost completely useless for many applications like my hovercraft project, which at the time I have posted this, is about 1 from the top.
On my Rikaline 6010, just reading the $GPGLL sentence, my longitude and latitude stay rock solid through the first decimal place, but the 2nd, 3rd, and 4th swim around (it seems that they advance and roll-over.)
At 33deg 38.6 min N, how many knots (or metres)·are 0.01 minutes longitude?
I don't know if this will help at all, but if you use "MGRS" you can get it broken down to centimeters if you can get enough satelites. It is the military grig system. We use it for, oh, everything. There are about a million web sites that explain how it works, and the services have been using it for years. The first five numbers give you the distance in meters north of a grid line, and the second set of five give you your distance in meters east of a grid line. Finding anything from there is just simple triangulation.
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--
And, in the end, the love you take
is equal to the love you make.
--
Well --·I haven't taken it outside, yet.· Maybe I should see how many SATs I have available and see if the other decimal places become meaningful.· There's a sentence available for SATs in view, but I haven't experimented with it.· It's only doing $GPGLL and its status is usually 'A' ( A = valid and V = invalid, where's the logic in that?).· What's the threshold for an 'A'?
My GPS doesn't have any kind of read-out, just RS-232.· I'm working on a Stamp routine to acquire the data, re-format it, and then dump it to an LCD (the PICanLCD.)· As it stands, the GPS just outputs to the LCD and it's confusing to read, but not impossible.
And for what it is worth, my garmin works as well in the middle east as it did in Mississippi and Vermont. I suspect it would have no problem with India.
I forgot to say this in my earlier post, but the biggest advantage to MGRS that I can think of is that each number in a grid coordinate is equal to something finite. 1 meter, 10 meters, 100 meters. It is easier for me to visualize one meter than it is to visualize one minute of longitude. http://www.survivaliq.com has an indepth description of how to read and use MGRS, but try to keep an open mind. It is easier than they make it.
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--
And, in the end, the love you take
is equal to the love you make.
--
I think there might be a little confusion going on, MGRS as stated is a different reference system than UTM. But this in and of itself does not provide higher accuracy, certainly not down to the centimeter for a civilian unit. The error introduced into the GPS system is through the time signature provided to units from the sattelites. This time signature is used to calculate flight time of the RF signal and thereby triangulate the unit's coordinates. Regardless of whether the coordinates are displayed in UTM or MGRS, the same level of error will be present due to the skewed time signature. You must either obtain a military GPS unit or employ differential GPS (DGPS) to obtain a higher accuracy of coordinates. The level of time skew is set by the military and its value changes according to the political and military climate, when we engage in activities against a foreign entity the time skew is turned up to reduce the accuracy of GPS based munitions employed by the foreign entity.
But India should have no issues with using GPS, most GPS units that state North/South America use are refering to the coverage of the vector map stored in the unit. The coordinate system is global but if used outside of N/SA you will not be provided a map, just the coordinates.
I got some batteries and have taken my GPS project·outside.· The receiver is out on the·patio and I have stable readings to the second decimal place.· I must be getting more SATs.· At the moment I have it facing the south.· It's still nearly 100F, today, and I'm reluctant to bake the receiver just yet.· Tonight or tomorrow morning I'll see how it does with "full sky."· ( BULLETIN -- RadioShack is selling a 40-count pack of "AA" for $20, Enercell alkalines, not the cheapies.· They have a similar deal on "AAA", too.)
Addendum: In "full sky", so to say, I still have 'accuracy' only through the second decimal place, the 3rd & 4th still hunt around.· I don't know to a certitude that it should be solid to the 4th, but I can live with it.
Comments
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
2. do we need to certify thru some regulatory authority to use GPS systems.
or any body is free to use.
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
Please explain this line in details.........
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
On my Rikaline 6010, just reading the $GPGLL sentence, my longitude and latitude stay rock solid through the first decimal place, but the 2nd, 3rd, and 4th swim around (it seems that they advance and roll-over.)
At 33deg 38.6 min N, how many knots (or metres)·are 0.01 minutes longitude?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
--
And, in the end, the love you take
is equal to the love you make.
--
My GPS doesn't have any kind of read-out, just RS-232.· I'm working on a Stamp routine to acquire the data, re-format it, and then dump it to an LCD (the PICanLCD.)· As it stands, the GPS just outputs to the LCD and it's confusing to read, but not impossible.
I forgot to say this in my earlier post, but the biggest advantage to MGRS that I can think of is that each number in a grid coordinate is equal to something finite. 1 meter, 10 meters, 100 meters. It is easier for me to visualize one meter than it is to visualize one minute of longitude.
http://www.survivaliq.com has an indepth description of how to read and use MGRS, but try to keep an open mind. It is easier than they make it.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
--
And, in the end, the love you take
is equal to the love you make.
--
But India should have no issues with using GPS, most GPS units that state North/South America use are refering to the coverage of the vector map stored in the unit. The coordinate system is global but if used outside of N/SA you will not be provided a map, just the coordinates.
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·1+1=10
Addendum: In "full sky", so to say, I still have 'accuracy' only through the second decimal place, the 3rd & 4th still hunt around.· I don't know to a certitude that it should be solid to the 4th, but I can live with it.
Post Edited (PJ Allen) : 9/18/2005 3:06:09 AM GMT