Looking for a GPS

[OOZ662]

However, not your normal kind. I've been tasked with finding a GPS system for use with Chief Architect, a house design program. It needs to output recorded Cartesian coordinates in a text file. Navigation and "joe schmoe" features aren't needed. We want to walk around a building lot recording locations and convert it into a digital image to build a house upon, meaning that it needs to be fairly accurate. Our budget is $400, though if we can find something cheaper we might be able to buy more of them for the class.

Any ideas? Lacking that, any suggestions on what I should specifically be looking for (terms and acronyms and such)?

[Wingnutt]

The military/goverment limits ALL civilian GPS accuracy on their end.  so no device you can buy will be accurate within a few feet.

Civilian GPS-based data collection systems use the civilian C/A code (as opposed to the military P code)

The U.S. military limits the accuracy GPS C/A code.
this degradation of the GPS signal (known as Selective Availability, or S/A) has an equal impact on all C/A code GPS receivers.

Accuracy of positions under the influence of S/A is that the horizontal coordinates will be within 100 meters of truth 95 percent of the time. And this is true regardless of manufacturer or price.

[Shuffler]

An insurance fella that came by my shop a few months a go had a nice camera with built in GPS to mark the coordinates on the picture along with direction he was facing taking that pic.

[AKHog]

Forget about it. Your idea of "fairly accurate" and the current top of the line consumer grade GPS units are magnitudes apart. Especially walking around an urban environment like "around a building" like you mention, your not going to get anything close to useful data with anything currently available.

For what you are talking about doing, you need a $15-20 thousand dollar GPS-corrected survey setup, and weeks or months of training and experience to use it properly. Search for something like 'Leica Survey equipment' to see what I'm talking about.

From your "for the class" comment I'm guessing this is for some school project? Was it suggested to use a GPS? What kind of class is it? I really think if they expected you to use this type of equipment that it would be provided or you would at least be educated about renting it.

I'd suggest for your budget you just get some very basic surveying equipment. You could probably even save your pops some dough and go to the hardware store and get everything you need for $50-100. You'll learn a lot more (probably the point of taking the class, no?) doing it the old fashioned way, too.

[OOZ662]

From your "for the class" comment I'm guessing this is for some school project? Was it suggested to use a GPS? What kind of class is it? I really think if they expected you to use this type of equipment that it would be provided or you would at least be educated about renting it.

You could probably even save your pops some dough and go to the hardware store and get everything you need for $50-100. You'll learn a lot more (probably the point of taking the class, no?) doing it the old fashioned way, too.

I think you took this the wrong way. I really could care less about Chief Architect myself, as I'm in the lab working on SolidWorks. The teacher of the class had me look into importing GPS data into the program. It's very possible, so he said "The school's allocated me $400 to buy one of these things. Have a look around."

We won't be walking around an urban environment. (Hell, we'd have to drive for half an hour to find one) He figures on doing something like having a student wander around the field out back (NOT a flat sports field, for you urbanites) of the school to take position data and pretend to be building a brand new house on that "lot." It's all about integrating real-world techniques into the class instead of constant paper/pencil work.

Interestingly enough, I was looking at one earlier that was supposed to be accurate within centimeters. I figure that was possible because of the equipment and likewise impossible because of the satellite limitations. It's rather obvious that we're not going to get something that will give us perfect data; your average home designer doesn't have that possibility either. However, the more accurate the better. That's what I meant by "fairly accurate."

[eagl]

Generic GPS devices that attach to computers use a standard interface that can be captured by any program that can log data from a serial port.  Heck, anyone remember those old dialup terminal programs we used to dial into BBS with?  Just point the terminal program to the serial port used by the GPS, and have it dump the data to a text file.  Some word or excel macros ought to be able to format it from there.

[OOZ662]

Exactly. Having never even seen a GPS in my life, I don't know what that feature is called. I don't know if there are ones that would do it without navigational and other such features (less features meaning less price). That's really all I'm asking here; what do I shove into Google?

[Stoney]

For $400 you could hire a surveyor to come out and give you the real deal.  And they'll survey with a GPS, at least around Reno they do.

And Wingnut, 1 meter accuracy is available for civilian use.  Otherwise the FAA wouldn't be able to certify GPS precision approaches.  They used to only allow 100 meter accuracy, and I don't remember exactly when they started broadcasting the most accurate stuff, but they do.  Plus, since the FAA is doing away with VOR navigation, you can bet that even during wartime, they'll still broadcast the 1 meter signal, unless there's some sort of calamitous event.  The Russians have their own GPS anyway.

[Wingnutt]

For $400 you could hire a surveyor to come out and give you the real deal.  And they'll survey with a GPS, at least around Reno they do.

And Wingnut, 1 meter accuracy is available for civilian use.  Otherwise the FAA wouldn't be able to certify GPS precision approaches.  They used to only allow 100 meter accuracy, and I don't remember exactly when they started broadcasting the most accurate stuff, but they do. 

  The FFA does not equal John Q public, Airline navigation has access to P code GPS, as does NASA and lots of other folks.. just not your average wal-mart shopper.

just because its military, doesent mean only the military has access to it.  the devices that are SA are your typical hand held  and vehicle, phone type navigation stuff.

[Stoney]

  The FFA does not equal John Q public, Airline navigation has access to P code GPS, as does NASA and lots of other folks.. just not your average wal-mart shopper.

just because its military, doesent mean only the military has access to it.  the devices that are SA are your typical hand held  and vehicle, phone type navigation stuff.

http://www.spacedaily.com/news/gps-00d.html

[Wingnutt]

http://www.spacedaily.com/news/gps-00d.html

yes, civilian GPS is far more accurate that it was WAY back during the Pre-Clinton era but not even close (for civilian use) to as accurate as it CAN be (military regulated P code GPS)  and nowhere nearly accurate enough for precise building survey work.  Clinton okayed what was (by todays standard) the removal of a VERY high degree of inaccuracy from the civilian market (think 1/4 mile).. but its is Still very far from as accurate as military class P code GPS.

a VERY simple way to put it is the number of places you can have after the decimal..     just for example (this is not even remotely exact)

Before clinton change  X: 32.882     Y: 12.834     Z: 10.228
After clinton (current)  X: 32.88254    Y: 12.83438    Z:10.22871
P Code military regulated GPS: X: 32.8827548    Y: 12.8349275    Z:10.2282107

thats of course not at all how it ACTUALLY works, but for the sake of getting the idea across.

[Shuffler]

I just know my new Samsung Memoir has GPS that works great.

[Marauding Conan]

Exactly. Having never even seen a GPS in my life, I don't know what that feature is called. I don't know if there are ones that would do it without navigational and other such features (less features meaning less price). That's really all I'm asking here; what do I shove into Google?

Do a search for GPS Construction Survey. As to buying it, if it is for school purposes, best route would be for the school district contact the manufacturer directly. They should be able to offer equipment for training to the school at no charge.

[eagl]

In most of the US, selective availability was dialed down so even a cheapo GPS ought to get you within a meter or two.  Of course, sometimes a cheap GPS will flat-out lie and not even tell you, and that's one of the major differences between a regular GPS and one certified for aviation use...  The aviation one should tell you when it thinks the data isn't reliable.