I have noticed various levels of resource/mapping grade gps systems from several vendors. The most frequent I have noticed is the group rated at 1-5m and the group rated at submeter. In the case of Ashtech the Promark X is rated at the 1-5m while the Reliance is rated at the submeter. What makes the difference? Is it possible to squeeze submeter out of a 1-5m system?
Shawn
In the mid 90's I kicked the tires on both the ProMark X and the Reliance systems. I chose Reliance for several reasons.
Reliance gives a choice of submeter, decimeter, and centimeter level processing depending on how much you spend and how much time you put into getting those levels of accuracy. If the ProMark X ever gets as close to the target as Reliance I think it would be an accident.
The SCA-12 GPS receiver that comes with Reliance can be used together with your other GPS tools in Ashtech Solutions. I have often used mine for static survey work.
The SCA-12 does an amazing job of locking SV's. I often tell people that my SuperCA will suck SV's right down out of the sky. I have used mine for rough mapping work in tree canopy where you would say no way you can get any kind of GPS here.
The company makes both and there may be some folks out there who prefer the ProMark X but my choice was, and is, Reliance.
I used Promark XCP/CM extensively (my first receiver) for wetlands, test pits and photo control. The Dos based software was simple, the win based MSTAR is harder to learn and use. The unit does not keep lock well under canopy with the quad antenna, but the 36db antenna from a Reliance picks that up...(so does a Skymaster antenna from Tri-M).
The issue is of productivity. Each separate position you get with a PromarkX is a separate file. You log one file per point..When you get back to the office you have to set up the processing software with a base file, an ephemeris file, the rover file, and a destination path for EACH occupation. This increases office time dramatically!!!On top of that you can append results to one file, but the format is not userdefinable like solutions or reliance.
The data IS compatible with Solutions in Rinex format. I still have one unit that I leave in the truck for a spare. It will let me get the occasional test pit or small job easily, will double as a static survey grade unit for carrier phase, uses 6 AA batteries but the external antenna eats them in a matter of a half hour or so...I use an external battery pack when doing statics. Reliance is more versatile, more accurate, and more reliable under canopy....
Remember, when the PromarkV and then PromarkX came out, they were the FIRST handheld receivers of any kind for the civilian market that would do post processed submeter. See the FGCS tests around 1993 or 1994 on the Promarks....At the time PromarkX-CP was $4500 per unit including software while survey/resource grade stuff was $9000 each plus 5k for software....They were cool units, but have been outpaced by technology...
Thanks guys, y'all answered my question just right. I'm really drooling over the idea of getting 1-2' kinematic accuracies that don't depend on maintaining lock.
Shawn