Trimble 5700 help!

What are you using to set up the receiver? A data collector? GPS Configurator? Configuration Toolbox?

It's possible, if your corrections are RTCM, that the grid definition and geoid heights are coming from the VRS Now. I would try the following two things:

- Perform a hard boot on the receiver to ensure that there are no Power Up boot files loading anything;

- Configure the receiver to use CMR+, if that's an option, not RTCM

If you start with grid coordinates using Trimble Access or Survey Controller, it defaults to orthometric height. If you use Lat/Lon, you get ellipsoid height. I have only used GPS Configurator or Configuration Toolbox a couple of times years ago so I can't say anything about their default settings.

I hope you don't mean that you're taking the RAW observables (either the .dat file or a RINEX file), processing them with OPUS and getting the orthometric height reported as the ellipsoid height. That would be a head scratcher.

On the other hand, if you're seeing this on a data collector and if your data collector is running the "Survey Controller" application, then when you're in Point Manager looking at the details for a the point, click on "Options" and select "WGS84" instead of "Grid." WGS84 always shows the ellipsoid height whereas GRID shows the geoid height if you have checked the "Use geoid model" checkbox in the job properties coord sys entry.

ssorcbor, post: 360330, member: 1963 wrote: If you start with grid coordinates using Trimble Access or Survey Controller, it defaults to orthometric height. If you use Lat/Lon, you get ellipsoid height. I have only used GPS Configurator or Configuration Toolbox a couple of times years ago so I can't say anything about their default settings.

That's true, but regardless they get broken down to ECEF Cartesian at the antenna phase center for transmission by the base; GGA strings should not be coming out of a 5700 in grid coordinates with ortho heights.

I assume that the GGA string you pictured is coming from the 5700 itself, not the data collector? It's hard to troubleshoot stuff like this without eyes on it.

Lee D, post: 360324, member: 7971 wrote: What are you using to set up the receiver? A data collector? GPS Configurator? Configuration Toolbox?

It's possible, if your corrections are RTCM, that the grid definition and geoid heights are coming from the VRS Now. I would try the following two things:

- Perform a hard boot on the receiver to ensure that there are no Power Up boot files loading anything;

- Configure the receiver to use CMR+, if that's an option, not RTCM

I'm using GPS configurator in conjunction with Lefebure NTRIP client to get TVN_RTCM_31 into the reciever. Yes, I thought that they may be coming through the VRS now too..

Ok i will try this, what do you mean by hard boot? Turn off and on?

Lee D, post: 360334, member: 7971 wrote: I assume that the GGA string you pictured is coming from the 5700 itself, not the data collector? It's hard to troubleshoot stuff like this without eyes on it.

Yes coming directly out of the 5700 itself

prettymuch, post: 360337, member: 11353 wrote: what do you mean by hard boot?

A hard boot is done by holding down the power button for about 40 seconds. After all the lights go out they stay out for 15 seconds, then the Satellite lite comes on for another 15 seconds. When it goes back out the hard boot is complete.

I suspect if you're using RTCM 3.1 the coordinate system parameters are coming across the VRS, there may be away to tell the 5700 to ignore this through GPS Configurator. Or if your VRS transmits VRS (CMR) use that instead of RTCM.

Tried the hard boot... no luck

I've just realised that the height is already corrected even before ive even applied the RTK!

Configurator lists the position Z as ~88m... then the GGA string is around 25m..

...weird

You will find that the GGA string does provide you an Orthometric elevation, also contained within the string is the geoid separation value. You may subtract the separation value to return to ellipsoidal.

Yeah, I was thinking this could be a work-around... I just dont know if its applying some kind of horizontal transformation...

I don't see how the 5700 could be putting out Ortho heights after a hard boot... there's no geoid model in it. The coordinate system info therefore HAS to be coming across in the RTCM 3.1 message. I don't have a way to run Configurator because you have to connect a receiver, but I would think there would be a way to tell it to ignore the coordinate system information.

Again, I can't speak to your VRS, but I would use CMR corrections instead of RTCM if it's possible to do so; that would fix it. We use VRS all the time with CMR corrections, and we don't get grid coordinates until we apply a coordinate system on the data collector or in software.

prettymuch, post: 360379, member: 11353 wrote: Yeah, I was thinking this could be a work-around... I just dont know if its applying some kind of horizontal transformation...

Why don't you want orthometric heights?

MightyMoe, post: 360411, member: 700 wrote: Why don't you want orthometric heights?

I just need to be sure its not applying a transformation..

Lee D, post: 360397, member: 7971 wrote: I don't see how the 5700 could be putting out Ortho heights after a hard boot... there's no geoid model in it. The coordinate system info therefore HAS to be coming across in the RTCM 3.1 message. I don't have a way to run Configurator because you have to connect a receiver, but I would think there would be a way to tell it to ignore the coordinate system information.

Again, I can't speak to your VRS, but I would use CMR corrections instead of RTCM if it's possible to do so; that would fix it. We use VRS all the time with CMR corrections, and we don't get grid coordinates until we apply a coordinate system on the data collector or in software.

Its very strange, the raw uncorrected from the 5700 IS giving me an ortho height.. there must be a geoid in there somewhere!

Ghost in the machine lol.

Hahaha, sorry. I read the message and my brain automatically went to standard base-rover RTK.

I should have added that the geoid value, and the corresponding Orthometric values found in a GGA string are based on the EGM96, or EGM2008 models. The proper way to work with a GGA string is to strip it back to ellipsoidal, and then apply a modern model such as Geoid12B.