sputnik2009

Hello there,

I have few questions regarding Topcon Hiper Pro receiver.

· Can Hiper Pro be used as a standalone receiver without any corrections from the base receiver or from Network RTK server? What is the accuracy?

Can I Obtain Accurate Positions Using One GPS Receiver?
· Which signals are tracked (L1/L2 C/A and P Code & Carrier)?

· Is TopNet+ same as OSNET in UK? Any difference between them?

· What happens if there is no RTK correction available? Is there any other way to correct? For example using SISNET or OSNET?

Hope someone can help me.

Thanks in advance.

GNSS

See comments above.

sputnik2009

Thank you for your reply.

Topcon Hiper Pro is a dual frequency receiver, shouldn't I have better accuracy then 7m?

Do I receive L1 and L2 or is it just L1.

What positioning data do I receive, RAW or NMEA?

Thanks again

GNSS

Even a Dual Freq survey type receiver in navigation (SPS) mode can only use L1 otherwise it would be a PPS receiver and that has to be a military receiver to make full advantage of L2.

The general accuracy even of a single freq recreational type receiver is normally goig to be less than 7m 95% anyway and a receiver like the Hyper will be a bit better again but mainly due to refined hardware/software, better filters, antenna etc

A civilian receiver can only receive L1 at the moment, the new L2C freq will allow civil receivers to be true dual frequency but this will not be for a little while yet and will also require new receivers. There are curently only 2 satellites capable of transmitting L2C and one of these is set unhealthly.

Not really sure what you are referring to here?

RAW data to me means propriety recorded format for latter post processing, formats like Trimble's .t01, leica MDB or even Rinex?

NMEA is ASCII sentence data sent from the receiver which is quite different to RAW(?) data.

sputnik2009

Thank you for your reply.

What I mean with Raw Data is, if you use Topcon Hiper Pro, will you receive the data in NMEA format or Raw Data when using Network RTK or RTK.
Is Raw data only for using in post-process?

By the way, why do they called dual frequency receiver? "Code and Carrier from L1 and L2" (Topcon Hiper Pro)

Thanks again.

gpsnetwerx

it depends on the network you connected to. in a traditional rtk environment - your base and rover- the base sends the rtk message in either cmr+ or rtcm 2 for topcon hypers. in the cors network environment i can send those along with an rtcm 3 "network (multi base)" solution, and formats specific to leica. this is typically shot thru the cellular networks.

"raw data" is sort of a catchall phrase that can mean different things to different people. "raw" data is the proprietary data format for a given sensor. the logged raw is available for you to post process. in my network, i can send the original raw data to someone that wants the "factory specific" format.

as for nmea, it is an output type message that can be used for many things and was developed as a specification that defines the interface between various pieces of marine electronic equipment. GPS receivers may be used to interface with other NMEA devices such as autopilots, fishfinders, or even another gps receivers. They can also listen to Differential Beacon Receivers that can send data using the RTCM SC-104 standard. This data is consistent with the hardware requirements for NMEA input data.

dual frequency is a sensor capable of receiving both l1 and l2. newer sensors are multi freq, meaning they will receive l1/l2 along with glonass, galileo and any other constellation thats available.

hope this helps.

cheers
scott

sputnik2009

Thank you for your reply.

I am still confused regarding the dual frequency receiver. Does it work with L1 and L2? And I guess it works only with carrier phase, am I right?

What do they mean with Code and Carrier from L1 and L2? (from Topcon Hiper Pro manual)

Sorry for all my questions.

gpsnetwerx

no problems

your hyper is a dual freq sensor, meaning it will track both freqs from the birds. additionally, it will compute from the actual code sent by the sats like any other handheld on the market. basically, time of signal flight divided by speed of light. this gives a distance. distance to 3 or more sats triangulates to a position. carrier or phase is different. here measurements are carried on the actual wave cycle where we can mathmatically divde the wavelength into ssmall peices. the wl for l1 is +- 19cm, l2 24cm. by playing games with the datat we can get very precice measurements.
in a stand alone methos, you hyper is not much better than a garmin. however when we difference with sensors at known locations then we can really split gnats A##es.

i can try to get you some links on carrier gps processing or just google it. if you still have ?'s let me know.

scott

sputnik2009

Thank you for your reply.

Raw GPS data is to post-process the data (RINEX). But when using (RTK) real time data (correction), then the output is in NMEA GGA, am I right? I am little bit confused in this part. Don't really understand this part.

Few more things I am confused about, RTK works with carrier phase, but why does it say code and carrier from L1 and L2 GPS and GLONASS in Hiper Pro description (Memory and Recording).

What is the Data output and input, RTCM SC104 or CMR+?

Would it be any difference in accuracy if you use single frequency receiver (L1) compared to using dual (L1+L2)? and how much is the difference in accuracy?

"carrier or phase is different" what do you mean by that?

What is RTK Carrier Phase Corrections? and RTK Pseudorange Corrections?


Is the receiver using code and carrier phase?

I am sorry for all my "silly" questions. Thank you again for your answer. I need to be clearer about few issues. I really appreciate all your help and I hope you can answer my questions. Would be glad if you can give me some good links.

Kind Regards

GNSS

No NMEA data is also basically processed data but in an ASCII format. RTK basically requires pseudo-ranges/corrections for each common satellite. This info is traditionally transmitted by radio using some form of communication protocol such as RTCM3, CMR/CMR+ or some form of manufactuer propriety comms format.

Hiper is a multi constellation receiver uses both GPS+Glonass satellites in a similar manner. Civil dual freq receivers "use" only part of L2 in a sneaky way. Futher civil dual freq receivers will be true dual freq using L2C. Many receivers today are so called "ready" for additional future constalletions (such as Galileo)

Previously covered. Used for RTK corrections and can vary in user accuracy depending on the system.

You don't state what sort of accuracy you are referring?

SPS (navigation type) accuracy will have very little difference.
Differential accuracy will vary dependent on methods. These being Static or RTK/Differential

You need to clarify what you require on this one.

Difficult to explain this in a few lines when you can really find heaps of info on this on the web.

RTK Carrier Phase corrections is the ability to compare phase of the signals to improve accuracy. C/A code changes phase at 1.023Mhz but the L1 carrier is 1575.42mhz and by aligning the signal then resolving ambiguties accuracy is improved.

RTK Pseudorange Corrections is the difference between the measured and known satellite distances that the receiving rover will basically apply for common satellites to resolve/determine the rover position more accurately.

A dual freq receiver basically is when used in RTK/differential mode. Code is 1.023Mhz, carrier is 1575.42Mhz

gpsnetwerx

if the mods will allow this link

http://www.resourcesupplyllc.com/pdf...eyGradeGPS.pdf

go and read. this is a simplified primer on rtk.

sputnik2009

Thank you for all help.

One last question, what is the difference in accuracy between RTK and NRTK? is RTK more accurate? I know with NRTK you can be mobile and no need to setup the base. But how much difference is it in accuracy between them.

Kind Regards
Alex

gpsnetwerx

no difference to speak of. the networked solutions are a bit better when the distances are longer. the advantage for the net rtk is efficiency.

sputnik2009

Hi again,
I have more silly questions

Why the need of 5 satellites when using RTK?
Static and Kinematic surveying, how would you explain these in a simple way?

gpsnetwerx

in general a minimum of 3 satellite for position, the 4th squares away the clocks and 5 or more builds redundancy in the the observables and strengthens the geometry for solutions. in a navigation world this is practically irrelevant. in surveying/high precision, more birds mean better solutions faster 3d fix etc.

static typically implies your rover sits over some point for a predefined period of time, generally used to establish hz/vert control. data is later downloaded and post processed against known reference stations

kinematic has a dual meaning. in the truest sense of the term, kinematic implies a moving sensor like a airborne mapping platform (photo/lidar). rtk, real time kinematic, is not true kinematic, ie the rover is not moving while observing. in rtk, correctors are broadcast to the rover in "real time" (like dgps) negating the need to process.

sputnik2009

Thank you for all your answers.

I need to write a report about this but can't find all information, need to be latest publications. Is it any chance that you know any answers to my questions below?

- All technical features of RTK and Network RTK.
- Review any blind or pedestrain navigation system which uses RTK.
- If not indicate the advantage of using RTK in blind or pedestrian navigation.
- State any limitations

Most important, have RTK been used for car or pedestrian navigation?

Thanks again.

gshan12

Furthermore, as alluded to above, a particular type of surveying known as "land surveying" (also per ACSM) is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats/maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.



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