Who's the number one GPS provider?

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http://sc.gpsworld.com/gpssc/article/ar ... ?id=479999

Interesting perpsective on who is the number one GPS provider.

I personally like Trimble the best, then Topcon then Leica. What are some others perpsective? what do you like best?

Trimble and Leica have most of the market in the UK, I think, as far as survey-grade equipment goes. I've only used Leica, both the 1200 and 500 series. However, Topcon have some good GPS equipment and it's reasonably priced. Trimble always seem overpriced to me, and not just the GPS.

In my experience Lieca has the best software when it comes to data management. There software allows you to use one data file for conventional and GPS surveys. I find they have a pretty weak radio setup that at times can reach no more than 1.6kms. Where as with Topcon and Trimble ive been able to get 16kms away from the base and still have a radio signal.

How do you like Leica? Do you find it very user friendly?

It's difficult to give an opinion on how user friendly it is, as I've not used GPS equipment from other manufacturers. It seems adequate, though. I was impressed with the 1200 SmartRover and the cellphone providing the RTK correction. It seemed just too good to believe, but is obviously dependent on the vagaries of the phone network. I mainly use the old SR530, to be honest and I've not had issues with the radio set-up, but most of the time the distances are less than 1Km. I did get the impression that range could be an issue after talking to the supplier, however. Also, I know different countries have different regulations regarding power and frequencies, so we may not be comparing like with like.

I only use Leica GeoOffice for post-processing static observations with RINEX data from the UK OS active station network if I need some OSGB36 control. So, I don't really explore its full functionality. I would say that the full dongle-enabled GeoOffice is rather pricey compared to Topcon's software for post-processing. For RTK work I just put the data straight into the ground modelling software I use.

What total station do you use?

In school we used Sokkia Set 410 Total station with an onboard data collector. It was not very usually friendly at all. Most of the class would get very frustrated with them including myself. Ive briefly used Leica and would one day maybe learn how to use one better. Ive heard good things about their total stations, being able to work on the grid with them etc. I think you can do the same with other total stations as well. I haven't used those functions of the total station to be completely fimilar with them.
I have the most experience with a Topcon GTS 225 total station. I have very little knowledge about their onboard data collector as ive never used it. The data collector i had to use with the total station was a Topcon FC 100 which i didn't find to be that user friendly, it had clitches mainly for the gps side of data collection. The biggest glitch was the data collector would reset the rover antenna height to zero from time to time which could result in a 2m bust in elevation when tagging and re-tagging a point. When ever i used a total station i always felt more comfortable and in control by booking my angles and distances by hand instead of using a data collector.

So with the SmartRover 1200 there is no need for a radio to apply the RTK correction? So the base setup would just be the reciever, required cables and a tripod? How far away from the base can you get using cellphone radio correction before the signal starts to fade and the real time coordinates become less acruate?

Do you do a lot of municipal surveying with GPS? What doed OSGB36 stand for?

OSGB36 is the coordinate system used here for most work that needs to be related to existing mapping. It was established using traditional surveying techniques. The remains of that are dotted across the hilltops of the UK in the form of triangulation pillars. The network has now been surveyed with GPS and there's a transformation available from ETRS89 into OSGB36. ETRS89 being WGS84 fixed to the eurasian plate in 1989. The 36 refers for 1936 when the last re-triangulation was started using traditional techniques. OS stands for Ordnance Survey. GB great Britain.

We use different terminology here, so what does municipal surveying involve?

All you need with the SmartRover is a cellphone signal, and the usual necessary satellite geometry. The cellphone connects to a server that supplies the correction that's been calculated from the OS active network. There's a fairly good density of those around the UK and the relative accuracy isn't much different to that when using the base with radio. You pay a subscription to be able to access the service. No cables, no tripod; just pole with GPS antenna etc. attached. It's not working with GLONASS, yet, though, but I think they're working on that. Does your kit use GLONASS as well as the usual GPS satellites?

I use a Leica TCRA1105plus total station. Again, it's slightly dated, but it's tried and tested, and does the job. It's a one-man robotic type set-up, and has got a laser distancer, as well, that's good up to about 100m. Everything's logged on an old PCMCIA card, like the GPS 500. You just need the right format files loaded onto the instrument for the software you're using to process the data.

I've got to admit that I get a bit paranoid about antenna and prism heights, so I know what you mean about the glitch. With both the TCRA1105 and GPS 500 you have to be careful because if you get part way through entering that particular information, then realise you've missed something on another screen on the options, go back, then return, it will default back to the last saved value. The TCRA1105 has also done some weird things with the laser distancer before and applied a prism height to that, but I make a point of double-checking height-critical laser data has a 0 value attached.

Does the GTS 225 have a laser distancer, or do you not use that in your work?

Municipal surveying deals with subdivisions and RPR's or Mortage Certifcates. Thats terminology im familar with. Its mainly surveys that deal with conveyance of property between two land owners. It also deals with construction surveys such as highways, roads, bridges, sewers etc.

Yes the Trimble RTK we use have Glonass capablities. We use Trimble 5800 recievers on some kits and R8 Model one recievers for some of our other kits. We also use some R8 GNSS recievers which are capable of recieving signals from the Galieo Satellite system that the Europe is working on as a part of GPS moderization, so it will be nice when the system is complete and up and running. Also capable of recieving the new L2C and L5 signals.
I however work in the office as a GPS analsyt, so at the moment i currently deal with TGO and DC file editor when doing Quality assurance on GPS RTK data. I used to work in the field.

The GTS 225 doesn't not have laser capabilites. The GTS 800 series does have laser capabilites as they are the Topcon's robotic series of total stations.

The Leica TCRA 1105 sounds familar, i think that is the type of leica total station i briefly used. I found it a very user friendly set up. If you couldn't tag a point with GPS due to trees or multi pathing, you could set two points out on the road or in clear visiblity with the GPS, store them in the data collector. Set up on one point, back sight the other, turn your angles and distances to the point under gps cover and the points get stored in the same data file. Streamlines the data very nicely.

How acurate to you find the triagaluation network?

I never use, or have used, the original OS triangulation points. Only the old benchmarks that were used for level only. I understand the transformation (OSTN02) into OSGB36 will tie-in to within about 100mm with the old network.

I've read some stuff on US surveying and I think you rely more on absolute positioning than we do. Over here most (but not all) things are just cobbled together on a relative basis. If you're going to survey an area for development and you're not using GPS, you'd also survey some surrounding significant detail like existing building footprints. You'd then paste your survey into some OS DXF digital mapping data to give it context using best-fit with that surrounding detail. The exception to that was with level (or height, elevation, whatever you want to call it) as that's critical for flood-risk analysis. For that you used to use the old OS benchmarks, but now you use GPS.

Yes we do rely on absolute positioning a lot. The RTK base usually is set up on a known control point with a UTM coordinate. We will then tag another control point for a check, then continue on with the survey. We rely on relative positioning as well when using static method over RTK method. I think we might be on the same wavelength.

OS DXF digital mapping sounds similar to parcel mapping in Alberta, which is a roughly calcutated township system. Its only accurate to 5 meters but is used when doing conventional surveys and section corners of the township system can not be tagged or tied in due to cost constraints. So instead of relating the survey to the actual postions of the section corners which define the quarter section the wellsite is within it is related to parcel mapping when drafting the plan. I don't agree with parcel mapping and i would always tie in a minium of three section corners to determine offset coordinates for well centre, no matter how much cutting was invovled.

How long have you been surveying for?

Yes, the second paragraph seems similar to what I was describing. I get the impression that legal boundaries in most of your country are defined by coordinates (correct me if I'm wrong), and so you have, by necessity, to use absolute positioning for most work. Over here many of our legal boundaries have been around for hundreds of years (before theodolites were invented) as we are a small densely populated country with a long history, and they are not defined by accurate coordinates, or even a line on a moderately accurate map. However, I don't usually get involved with boundaries so I'm perhaps not the best person to comment on them.

As for the last question, I'd rather not give that detail publicly, as I feel I've gone a little too far already. How about yourself? (Perhaps you're not as paranoid as me!)

No they are not defined by UTM coordinates, we obtain UTM coordinates from provinical 3D control networks to start our RTK survey, then we tie in the section evidence which then puts UTM coordinates on the section evidence but those coordinates arent added to the control network. Our legal boundaries were surveyed using chains or steel tape and theodilte.

I understand. Would you be more comfortable continuing this conversation via PM?

Okay, that still ties in with what i'm getting at, I think. Were those boundaries then related to a network of regional or national survey monuments? If so, that seems to explain the difference in approaches between the two countries in that you can, and often need to, position relative to an existing control network. Our legal boundaries do not, generally speaking, relate to any control network, and so relating surveys directly to the OS triangulation points was not, and is not, so critical.

I'm curious now, in an average city in your area, at what density do survey monuments exist for traditional surveying techniques? And I mean those that are state approved, as it were. By state I mean either national, or local government.

Yes, we can continue by PM, if you wish.

Trimble is the best brand for GIS fieldwork. As for navigation systems found in cars, I would probably guess OnStar.

OnStar is offered primarily on GM vehicles in the U.S. (Chevrolet, Pontiac, Buick, Cadillac, GMC). My dream vehicle is a Buick Enclave, so I am a bit biased here.

Tim