Cellular RTK suggestions

If you are just buying the sim cards you shouldn't need to sign a contract. Of course I have been wrong before.

Maybe I'm not quite understanding the specs for the job but why cant you use VRS and measure some of the existing points as well as all of the new points.

That way you could adjust all of the new points to match the datum of the existing points.

Yeh, I know.. but the client has his requirements and VRS is not an option, trust me.. I've asked.

I have an verizon raven airlink that i am not using any more , will sell if you want fairly cheap email me.

Do you have any idea how I'd transfer service on it? I guess it's a modem and has an ESN that I just call and request service on? Any idea what the monthly service cost is? Was a contract required for your usage?

Maybe I'm not quite understanding the specs for the job either, but why cant you use RTK and conventional radios and "leap frog" the base as you need? I can get 2 miles easy from the base, which gives a four mile jump. Maybe all wrong for your project, but it will work if nothing else does.

I use GSM equipment for this very reason, can put a SIM in each of the modems and go to work, they can be in a phone the rest of the time, NO dedicated ESN on the network! I use T-Mobile normally, BUT have an AT&T SIM also I can add a block of data to and go to work, neither carrier requires a contact that I am aware of. Yes if going over IP you will need a static IP at the base or use a DNS (I think that is waht is called). I am able to use CSD data over T-Mobile, although I sometimes have issues connecting because I think the carriers detest CSD users AND my theory is that gets bumped for more "important" network traffic. I use Leica gear and have a pair of dedicated modems for my network connections for RTK.

SHG

You have to shake your head in wonder at such requirements. A VRS would probably get you better results than what you are proposing.

As best as I can figure your approx. 60 sq miles is a box approx. 8 miles x 8 miles and if you had your base setup some where near the middle you would be max. 6 miles from it at the edges.

A high powered radio might reach the best part of that if you had a nice elevated spot to put it on. Maybe three or four setups with one of those would cover your area.

Instead of VRS, can you use single baseline from your RTN? You are basically talking single baseline anyway, if you are going to do base/rover via cell. Seems like single baseline would satisfy the requirements of a direct tie to control. If you have a few CORS nearby, you can do Single baseline to multiple CORS, and get an adjustable network.

[sarcasm]lightsquared[/sarcasm]

Do you mean the project is 60 miles by 60 miles? Because 180 points in a sixty square mile (<8x8) is a very high density unless it is very long and skinny.

Anyway, you mention the job taking a month so I suppose there are other tasks besides just "control". In a month there's at least 20 working days so that's only 9 points a day, plus whatever else you will be doing.

When I work on similar projects, I set a base where I can reach as many planned points with a two/three mile vector, then at each target location I set my center mark ( PK, nail, rebar), set up my antenna, then collect GPS data while I lay/paint the target, being careful not to disturb the setup. Unless there is an obstructed sky, 15 minutes always gets me enough data to get a good static solution.

If you can drive to the points you will get 2-4/hour. Looks like 60 to 80 hours work counting time to move base locations. I would have estimated a long week in the field to take care of control needs on your project and that includes targets. If you are in West Virginia or a like state it will be longer.... if in Kansas maybe shorter. The time it takes to get to the points is likely the most important factor in how long the job will take.

If you are in a wooly area with bad access, it makes all the more sense to use static. Nothing worse that getting way out to your point after winding through a mile of two track trails to find your radio/cell signal doesn't reach because of terrain blockages.

Sometimes I wonder about the boy geniuses that write survey specs that rule out VRS but allow RTK??? Why don't they just establish a reasonable accuracy requirement and let you, the professional, decide on methods and procedures? (could go on a real rant here)

Well, whatever you end up doing, congratulations on getting such an interesting project and good luck.

to transmit you RTK base raw data to the rover you can use free NTRIP caser
te receive raw data from base and forward them to rover you can use free NRTIP client

Never tried this combination. What it seems like you need two smartphones with Internet. I think you can run the Caster on a laptop in your truck connected to interned via Android (or other phone type) hotspot. but I am not sure if mobile Internet provider will allow you to sent data over Internet. On the rover end you would need Android phone running the Client program. If you have an office in the area than it is easier to setup base but I do not know if length of distances will not be an issue

I am just guessing .. it needs more research. I wrote here how to use the Caster but search does not pop up anything.

Terrain makes a lot of difference in production! I just proposed on a project where I estimate round trip from a base station to some of the photo control points is going to be 3-4 hours, project is about 13 mils x 13 miles BUT in forested steep terrain with several major drainages. Only a couple of the points are on the same road system, the rest you have to back track to get to a different ridge line or to cross a drainage. My time estimate was 26 hours for NINE points and 700 miles of dirt road driving for a single occupation, double that to add a second occupation. I will for sure be collecting static data even if I have the radio running just for a fall back plan, no CORS , no cell service, 50+ miles to nearest small town with a place to stay. Sometimes it is more about the journey than the destination!

SHG

I really like RTK but I'd still consider static for this job. I don't know how far the baselines from base to rover will be, but I've had pretty good success with 5 minute occupations over several miles with dual frequency receivers. If I were doing it with RTK, I might do 3 minute occupations so the net savings is minimal considering that your travel between points is probably your most time consuming, even at 10 minutes per point for static occupation, you'd be doing pretty well.

I only suggest this because real-time doesn't sound like a necessity for the project as you've described it, except for the warm fuzzies that come from good statistics while in the field or fast results in high-traffic target locations.

:good: :good: sounds like a good one... hope you get it.

A year ago I was able to provision two 'Pay as you go' ATT SIM cards and have them work. I bought them with cheap phones at wallyworld and at the end of the two week project, just let them expire.

I now believe that I could have gotten the sim cards for free by calling ATT, and could have signed them up for 1 month's service and then canceled them.

The real trick in all this is I had to set up a IP forwarding system here at the office: basically I used GNSS Surfer to input RTCM 3.0 corrections on port 2100 and then cast them back out port 2101.

I had to do this because you don't end up with static IP numbers on the base. We have a static IP at the office so the base sends corrections into port 2100 and then the office repeats them back out 2101, the rover connects 'Direct IP' to 2101 and gets the corrections.

There used to be a CPD service that would assure you of a static IP address on the base, but I don't think that it is available in my market anymore. (Or if it is, I can't find anyone who will sell it.)

Good luck!

Mark

.. it showed up, this is the [msg=176510]link[/msg] the last post in the tread shows how to set the caster up.

Yeh, I think I'm giving to give your suggestion a shot, if I use two or three rover receivers and set them up, then go back and move the first one and repeat.. I'll spend my days driving back and forth but not sitting at the stations waiting. Let me ask you a question though, I've always followed a rule for observation time: the distance in kilometers plus 5 minutes. So if my baseline is 5km, I do a 10 minute observation. Do you use something similar?

I can see many uses for these modems but the cost is just silly expensive when you run the numbers.. doesn't make sense for a pair of jobs.

Please don't just take my word for it but I've had good success at 5 miles with 5 minute occupations. I would have to look at some old files to see. I probably would do ten just to be sure. I wouldn't reobserve all of them. Just enough to get a feel for repeatability or questionable sites.

It wouldn't take but an afternoon to go out and test it. You might be surprised. Set up the base drive out to a point that would equal your longest line in the project and shoot it at five then ten then maybe fifteen. Do another point halfway. Same thing. Go back to the long one, five ten fifteen then the middle one same thing. How do they compare? How did the five do compared to the fifteens? You'll have a good feel for what your units and software will do. Of course logistics will probably dictate your actual occupations.