I really delight in doing webinars and the RTK network webinar on April 21 become no exception. probably the most explanations I basically savour them are the questions and comments I receive because it offers me some feedback as to what the user group is considering and questioning about. naturally, RTK networks are a scorching subject matter these days. The registration for the RTK Networks webinar become one of the vital maximum in historical past for GPS World.
if you missed the webinar, you could still down load the file and listen to it.
Now without additional ado, following are questions that listeners despatched in and my feedback from the RTK Networks webinar.
question #1: can you say the rest concerning the proposed countrywide Geodetic Survey precise-Time Networking (NGS RTN) instructions?
Gakstatter: The NGS continues to be within the early degrees of constructing the RTN guidelines so the company would select public comment be withheld at the moment. It’s are engaged on guidelines to cover 4 areas: web site issues; planning and design; administration; and clients. The company has assembled somewhat a group of government and business individuals to boost these instructions. The crew hopes to have draft types able by means of September 30, 2009.
despite the fact, the NGS actual-Time user guidelines (Ver. 2.0.four) is available to the general public. though these instructions are focused at classical RTK clients (non-RTK community), it consists of some solid processes.
also, a captivating study become posted currently by way of Newcastle tuition Civil Engineering and Geosciences selected to network RTK. Stakeholders within the document include The Survey affiliation (UK), Ordnance Survey (UK), Leica Geosystems, Trimble, and Royal Institute of Chartered Surveyors. They did some extensive testing and generated fundamental guidelines:
Their strategies make loads of feel to me. doubtless the most controversial is the separation time (forty five minutes versus 4 hours) between periods. this is in opposition t most normal practice that I’ve examine, however then again I don’t have empirical records to aid it both manner, whereas the file does. it is naturally a neighborhood that needs a better look. The time reductions within the field can be reduced significantly for environment secondary handle if this follow became adopted.
query #2: What manufacturers for RTK-community implementation would you recommend?
Gakstatter: neatly, there aren’t many decisions. The market is dominated with the aid of Trimble and Leica Geosystems, with Topcon on the perimeter.
I don’t comprehend if any person can say with self belief which one is better from a expertise standpoint. I’ve used rovers on all three networks and all looked as if it would behave as anticipated.
each Trimble and Leica networks have been applied in giant geographic areas (state-extensive, nation-vast) in order that they’ve experienced the growing pains and most likely have worked out any most important issues.
there are lots of issues apart from which community software dealer you opt for. a large one is the information expertise (IT) element. with out help from your IT department (or manage over IT with a reliable IT mission supervisor), getting a network to run easily might be a really rough road. I don’t faux to have long gone in the course of the technique of surroundings one up, but I’ve talked to sufficient americans to understand this is a standard theme amongst them.
query #3: How distinctive is the RTK processing for network versus cluster?
Gakstatter: A cluster is essentially a bunch of reference stations install in a geographic area. The consumer selects which reference station to make use of (always the closest one) and receives corrections just like a person would from a reference station he install himself. Communications from reference station to user is generally completed by the use of UHF/VHF/spread spectrum radio or instant network (GSM, CDMA).
With a network, information is accumulated by using all reference stations and sent to a significant server where the statistics is processed; corrections are generated and sent to the user. subtle atmospheric modeling is accomplished and integrated into the corrections. In idea, this eliminates distance-elegant errors within the network.
query #5: Does any individual be aware of of some other posted RTN user guidelines?
Gakstatter: See answer to #1. The Newcastle school document is accessible right here.
query #6: could you talk a little about submit-processing?
Gakstatter: neatly, it’s a field worthy of extra space than can be accommodated right here, however it certainly has its location in atmosphere basic survey/geodetic manage and is the favorite formula.
additionally, single-frequency GPS instruments are nevertheless the cost leaders for entry-degree GPS surveying. Even today, many individuals use GPS L1 contraptions with put up-processing for accumulating topo survey information.
query #7: they are in Philadelphia and they use the Trimble VRS network. They down load and import a .dc file into Trimble office. I don’t think as confident the usage of this network as I did once they got an OPUS answer and adjusted the bottom station. method-sensible, do you have any advice on the way to catch the facts? we're doing a morning session and an afternoon session and averaging the effects.
Gakstatter: I deferred to invoice Henning who's the RTK community expert with the countrywide Geodetic Survey. NGS has developed RTK consumer guidelines. here is bill’s opinion:
“RTK will offer you coordinate assistance and not a whole lot else. which you can set the records collector to keep covariance records, that will can help you dump the facts within the workplace software and basically function a tweaking of the coordinate positions if in case you have redundancy in some form (yet another place on the aspect of pastime). i might by no means use only one RTK location for any huge factor — there are too many variables. Any point that you're going to reuse or it is critical in itself to the job may still be found redundantly (see the summary table in area V. of the single base instructions). additionally, any factor whose elevation is crucial to lower than 3 centimeters should be leveled (or produced from a total station shot from a favourite element, and the like). In a further vein, average RTK accuracies (say 0.03′ horizontal, 0.05′ vertical) will also be performed through a localization to normal and trusted passive monuments surrounding the task.
My advice for a assignment web page without present depended on control can be:
query #8: How do you feel in regards to the appropriateness of RTK for “boundary” places? What QA/QC will also be executed within the container?
Gakstatter: Many surveyors i know use RTK for surroundings boundaries. Some even use single-baseline RTK for this assignment, which is well-nigh just a radial survey (no redundancy). I’d say that almost all who i know which are doing this have used their RTK programs enough to take into account the barriers. really, I consider most have run RTK and complete stations aspect-through-facet on jobs to benefit confidence and be mindful RTK within the field.
I’m certain I’ll get blasted by means of some folks for now not downplaying RTK for picking boundary places, however I don’t consider it serves any goal to ignore what’s actually going on within the field. there is so an awful lot drive, above all in these financial times, to cut back box time and raise efficiency that RTK ends up filling that need.
At a minimum, i might occupy each aspect at least twice with the bottom station install on two distinct monuments. in case you’re the use of corrections from an RTK network, I’d occupy twice with a 4-hour separation between occupations (as an instance, as soon as within the morning and once within the afternoon). I’d even dump the antenna a few times with every occupation to get two or three “sparkling” measurements.
The above assumes that you've a transparent view of the sky (no blockage by means of timber or buildings), are tracking at the least six GPS satellites, and have a PDOP of 3 or much less. if you’re up in opposition t a tree line, tracking five satellites, and the PDOP is 5, I wouldn’t settle for it in spite of the fact that the RMS indications looked good.
I’ll depart at that for now, as I may write a column just on this discipline. I actually would no longer guide somebody new to RTK to cut their tooth on boundary places. I’d imply constructing self assurance and event with RTK on purposes where there's extra wiggle room.
query #9: could you tackle the capability of the RTK community or cluster to adequately provider dynamic surveys verses static?
Gakstatter: Dynamic is in reality the concern here. In my journey, there are at the least a few considerations to be privy to.
query #10: it is possible to make use of a single-frequency receiver as a rover within the RTK technique, or it's a limitation?
Gakstatter: I’ve acquired simply a little event in attempting to make use of L1 RTK on an RTK community. It didn’t work very well for me for centimeter-level accuracy, however labored adequate for sub-foot accuracy.
L1 RTK programs frequently have some particular needs to ensure that them to work optimally. for example, some are capable of make the most of SBAS satellites as observables. RTK networks don’t support this class of observable (as a minimum the ones i know of), so gold standard efficiency from L1 RTK is finished when the consumer operates his or her personal reference station as a substitute of the use of an RTK community.
question #eleven: you should focus on the merits of the use of PPP if a reference survey monument is not available when establishing/initializing RTK.
lign=”left”>Gakstatter: PPP (precise pointing positioning) is a really wonderful discipline and i intend to dedicate a column to it in a couple of months. in the meantime, GPS World Contributing Editor Dr. Richard Langley supplied a column on PPP in the April 2009 challenge of GPS World.
query #12: For the states out west, any challenges you are aware of in participating with the PBO on upgrading stations to true time and receiving the uncooked statistics?
Gakstatter: Plate Boundary Observatory (PBO) has a big variety of reference stations within the Western u.s., I think more than 800. I’ve spoken to a number of distinctive RTK community directors in the Western U.S. who've integrated PBO reference stations into their RTK networks. The standard consensus is that PBO web page communications is the most important challenge. RTK networks require that the facts flow travels from every reference station to the network server after which to the user inside two seconds, so respectable communications is terribly important. PBO websites weren’t designed for this form of communications in intellect in order that component needs to be upgraded to ensure that it to serve in an RTK network.
for brand new PBO websites, I’ve talked to an RTK network operator who has collaborated with PBO efficaciously in constructing the site and together with “RTK-network suitable” communications amenities right through web site building.
query #13: Do you foresee penetration of GNSS RTK network know-how in mass-market applications equivalent to place-based functions (LBS)?
Gakstatter: no longer within the near future. LBS don't seem to be yet as lots about accuracy as they are about applications — primarily navigation, family unit tracking, and social networking functions but many more are to return. None of these purposes require the excessive diploma of accuracy that RTK networks are developed for.
query #14: what is the estimated number of users in the united states? Say this yr and three years later.
Gakstatter: I don’t have particular numbers, however i might say that here is one of the most quickest growing areas in GNSS. It crosses a variety of industries akin to survey engineering, building, mining, and agriculture. additionally, laptop manage is anticipated to develop global at a CAGR of 23%-28% within the subsequent five years and true-time positioning is a vital component for this.
query #15: Does latency in telephone indicators have an effect on accuracy in clusters or networks?
Gakstatter: yes, very an awful lot so. The industry standard latency ceiling appears to be two seconds from the time the facts leaves the reference station, travels lower back to the server, is processed, then is got by way of the user. Any hiccup within the communications manner will affect accuracy.
query #sixteen: Their network lately performed a readjustment. This shifted the H by using .08′ and the V by means of .10′. when you are the use of the network for actual property boundaries, do you are looking to stay on a present epoch? Or have your own home circulation with the crust, consequently forcing recalibration on each readjustment?
Gakstatter: once more, I deferred to bill Henning who is the RTK network expert with the country wide Geodetic Survey. NGS is setting up person and administrator instructions for RTK networks. here is bill’s opinion:
“What has came about is both the RTN essential to be readjusted to be greater correct — because of new information, in all probability — or the RTN adopted a brand new realization [say NAD 83(NSRS2007) from NAD 83 (HARN)], or because of massive stream of the stations it become felt the coordinates should still be maintained as current instead of at a prior epoch. For some thing factors, you can see that the metadata on the RTN stations would be crucial to constant positioning. because as the NGS CORS network is referenced to a selected epoch of time (ITRF 2000 cognizance of the ITRS at epoch 1997.0 modified to NAD eighty three realized at CORS adjustment 1996 at epoch 2002.0), with velocities presented in each datums, the person can place from these stations to his epoch of survey through applying the shifts in coordinates produced through applying the velocities. All RTN may still do the equal.
“we have been spoiled in many of the united statesA. by means of having a datum that strikes with us and therefore has little residual circulation relative to their place. NGS is now relocating in opposition t adopting a real geocentric datum aligned either to a definite epoch of a definite ITRF recognition and glued on a good North American tectonic plate, or one on the way to adopt the global velocities referenced in the ITRS datum. To be constant, surveyors (and all geospatial authorities) may still be sure to provide the proper metadata on their work, in an effort to state the coordinate datum basis, source of coordinates, epoch date of the coordinates, estimated velocities as posted, and even if the distances reference grid or floor coordinates. they could choose to provide coordinates according to the epoch date of the RTN or they could give them for the date of survey, however they must supply the metadata for those following afterwards — including planners, designers, engineers, GIS, and future boundary retracers.
question #16: Will network RTK win (render out of date) or enrich SBAS?
Gakstatter: I don’t suppose so. SBAS (WAAS, EGNOS, MSAS) became designed and developed to serve the aviation community. that is a separate and distinctive gadget that might be stand-by myself. Aviation navigation device infrastructure won’t (and shouldn’t) share supplies like they do within the commercial sector. Aviation navigation infrastructure needs to be a stand-by myself system beneath full control of the governing aviation authority (for example, within the united states, it’s the Federal Aviation Administration).
query #17: Are RTK clusters/networks offering capabilities for clients that had been as soon as best obtainable during the country wide Differential GPS stations?
Gakstatter: no longer really. NDGPS is one supply of DGPS corrections. WAAS is a different supply, and there are additionally industrial DGPS correction providers reminiscent of OmniSTAR. RTK networks are a different that can also be added to the checklist.
however RTK networks were created to give centimeter-level accuracy. they are also in a position to supply DGPS corrections (sub-meter accuracy) like NDGPS, WAAS, and OmniSTAR. however in contrast to NDGPS and WAAS (which might be free), it prices funds to make the most of an RTK network. although a subscription to an RTK community is free, the user still ought to pay for entry to the GSM/CDMA network.