Also look into an intuicom rtk bridge. It helps a lot
I don't know if any carriers support circuit switched data (CSD) any longer vs packet data via an IP address or not. My first work using a cell modem between base/rover was pre RTN's approximately 15 years ago, I just set my base up and then dialed it with my rover, used the phone number of each. I haven't done that in many years.
I now use an Intuicom ( http://www.intuicom.com/survey-and-machine-control-products ), they have a base-socket mode that allows you to "call" the base over IP from your regular rover modem, very slick if you want to use phone network BUT are outside a RTN coverage area or just prefer to run your own base station. There are probably less expensive ways to do this, BUT the Intuicom is plug and play AND you also get a low power radio that will go several miles line of sight in one package. I now have two of these in the survey wagon for all kinds of scenarios as repeater, or Intuicom to Intuicom over cell network with broadcast corrections for a short distance to the rover, etc.
SHG
I appreciate all of the comments on this, as now i have gone from a person that has never used cell modem for anything, to now believing that it must be the best thing around. with the right setup and equipment and knowledge
Not sure I mentioned it earlier, but I currently use a way outdated sp epoch 25 for my base along with a 35 watt pdl and an epoch 50 for the rover, which it was a trick to get the 2 to talk together.
Normally can get up to 5 miles range but varies, in messing around time, in a flat area at night, was able to pick up base radio nearly 20 miles away, which brings me to my next question, with cell phones there is huge difference between that and using radios, when it comes to range, although I am not necessarily looking for a schooling on surveying 10 to 50 miles from my base, i was curious what is typical comfortable range one can get using the base rover via cell modem correction and also the network scenario, if a person is able to get cell connectivity, is there a range limitaton? and if so is accuracy degradation an issue and at what point, this was not much of a question with radios because of obvious radio line of site limitations or other factors, if you could pick up the radio from the rover, you could survey, I have a hard time seeing the limitations of the cell scenario
The "official" range limit for single base RTK is 10 kilometer...or 6 miles...as I have seen published in various un-named sources.
I like to stay within that range for reasons of accuracy and initialization times. Yes I have observed and verified 20 mile shots.
John, disregarding the accuracy scenario, does that 6 miles hold true with cell modem as your base transmitter, I understand that 6 miles does push the limits of uhf radio distance even in my world where there is little cover and generally flat terrain, especially if attempting to use the fcc required spacing and baud rate combo, I barely can get 3 miles under the legal requirements, the primary reason for this post and my questions is that I currently use a pdl, which and still have an epoch 25 rover and 50 rover, unless i am missing something the pdl radio does not comply with current regulations, but since I will be purchasing new or used equipment that has the newer transmit and receive radios, plus internal cell, I felt it was reasonable idea to find out about cell modem used as base, untill a week ago, i did not know it was possible, I was thinking it was uncharted territory or rare scenario, as it would be nice to be able to survey up to 10 mile radius without constant struggle to maintain or be able to reinitialize, either way in most cases I try to keep a continuing line of shots along a center of road to help me later on to determine if for some reason I was getting way off line. about 3 years ago, I replaced a data collector, with the exact same unit, but did the setup myself, I neglected to put a geoid in the unit and had setup the base without it, not really thinking about the geoid, then went to ablilene area where i was surveying a new location for a house in kind of a mountain area, for vertical and horizontal, of course when i surveyed the place I really did not notice a problem till checking vertical, it was all over the place, the bad thing was so was the horizontal, but it took me 3 trips to figure out what i did wrong, I would not have guessed that would have made such a difference, but i found horiontal positions differences on every shot, i am talking about several feet, even if the shots were 2 feet apart on the ground, without the geoid they may have been 20 feet apart via the data
that kind of veered off subject, but may still be good info for some, i had to go back to several jobs to find out how many i may have screwed up before i caught the problem, to my knowledge that one job was it, and i was within half a mile of my base, I could not figure out a way to fix the data as a simple transofrmation only moved all positions, but did not correct the overall problem, that job was not a normal 100 to 200 point house survey, it was a huge topo of near 1000 shots on approx 10 acres, hard lesson to learn
while I have gone further when needed, I like to keep baselines (both fast static and RTK) under 15 km. If I have to go further I will extend the time of the session if it is static (1 minute per kilometer is my minimum criteria, with a 15 minute minimum always). If doing RTK, I will do multiple re-inits and 180 second occupations (Observed control in Trimble-speak).
Most of the time the 15 km limit is pretty easy to maintain, but there are times when doing photo control for example that there might be one or two stations outside that limit, and it doesn't make sense to set a new base. I have gotten good repeatable results at over 30 km, but I try not to push it that high. It matters what the weather is like, if there is a front in between (i.e. different conditions at the base and rover), etc.