NTRIP - PPK Survey

[tatiana.andreeva]

Hey there,

I’d like to clarify some points regarding conversion ETRS89 data to WGS84.

Both RTKLib and ReachView calculate a rover’s position relying on a base’s coordinates. Basically, the rover knows the centimeter-accurate distance to the base while it’s maintaining the fixed solution.

If the base position is shifted on some offset from the real point on Earth, all rover’s coordinates will be shifted on the same offset too. That means that if the base’s position is specified in WGS84, all the rover’s measurements will be in WGS84 too. If the base coordinates are specified in ETRS89, all the rover’s measurements will be in that coordinate system too, even if ReachView and RTKLib will consider it as WGS84.

Sorry for misleading you earlier! I hope this explanation will clarify things a bit.

[kasanmascheff (SK)]

Thank you Tatiana for that input.

I try to make sense of it in my case:

Base RS2 - receives real time corrections with NTRIP in ETRS89

M+ on drone (without correction input) for PPK Mapping

Procedure for PPK Mapping:

Simply correct M+ Rover data in RTKpos with RS2 data --> that’s it?

It has been proposed to use the position from RS2 base (from survey mode or also from RINEX raw logs header) for RTKpos position of base. — If I understand you correctly, this is not necessary?

Results will all be automatically in ETRS84, correct?

[tatiana.andreeva]

Hi @kasanmascheff,

Yes, the process should be the following:

1. Find out the Reach RS2 position in RTK with NTRIP (it should be in ETRS89 as long as you’re getting corrections from the base in ETRS89)
2. While processing, enter this position in RTKPost => Options => Positions => Base Station => Lat/Lon/Height (deg/m)

As the result, all the data should be in ETRS84.

[kasanmascheff (SK)]

How do you recommend to get the EXACT position if no point has been placed in survey mode?

Can I also take coordinate from solution pos file?

[kasanmascheff (SK)]

I guess the answer is yes:

Survey point of base station (pink) and points from solution .pos log file in LLH --> same CRS

This log was made in ideal conditions (skyview wise).

[kasanmascheff (SK)]

@tatiana.andreeva:

When putting in the base coordinates in RTKpos, do I have to add the antenna height if taking the ORI value from RTKpos?

I

[wizprod (Christian Grüner)]

@kasanmascheff

When putting in the base coordinates in RTKpos, do I have to add the antenna height if taking the ORI value from RTKpos?

That depends id you have corrected it in the previous run? You should never double process the antenna height so to speak.

I usually process the base point, so I have the resulting point’s altitude without any antenna-height. That means that I always enter the antenna-heights when processing.

[kasanmascheff (SK)]

In this example, the data shown in RTKplot are from the solution file .pos that I donwloaded from Reachview. To my understanding that would mean that, this is the z-position of the antenna, meaning that I have to correct for that in RTKpos when PPK the rover data.

[tatiana.andreeva]

Hi @kasanmascheff,

@kasanmascheff

In this example, the data shown in RTKplot are from the solution file .pos that I donwloaded from Reachview. To my understanding that would mean that, this is the z-position of the antenna, meaning that I have to correct for that in RTKpos when PPK the rover data.

Yes, you’re right, you should specify the antenna height in this case. Please note that antenna height is considered as pole/tripod height plus 0.134 m (the distance from the antenna’s bottom to Reach’s bottom).