Mapping and GIS Solutions Community

Hi,

The organisation I work for has historically used a Zephyr 2.0 receiver with a handheld Geo7x to both find and map points with 1cm accuracy. We specifically use these instruments for long-term agricultural field trials, some of which are over 100 years old, so accuracy is important and we need it to be within 1cm because this is also the tractor systems work to (also some of our trail plots are only 1m by 1m, so even 10cm can make a big difference).

With a lot of help from our IT team around software compatibility, the Zephyr/Geo7x system has worked really well for us over the last 10 years, but as they are now switching off the 3G network in the UK, we need to upgrade and have chosen to pair a Trimble DA2 receiver with a tablet that runs QGIS/QField. 

My problem is that I cannot get the two systems to find the same point location with 1cm accuracy. To test this we uploaded the same map (in WGS84) onto both systems and marked out several points using the old Zephyr/Geo7x. I then tried to navigate to these points using the DA2 and QField, but was consistently about 20cm out (see below photographs). I am almost certain there is a difference between the settings but I can't figure out what it is. Below is the device setup as I have figured it out on both systems so far. 

Any insight anyone has would be hugely appreciated. 

Hi Aislinn

This looks like a datum shift error which should be easily fixed

If your GNSS output in TMM = Auto in the UK, then this will be using the OSNetv2009 (2009.76) datum, BUT your data and QGIS If understand correctly are using WGS84

This will add a shift in decimetres (depending on where you are in the UK) between your GNSS position and the data. 20cm sounds about right

In TMM try this

• Under the GNSS Configuration menu
• Change your GNSS OUTPUT to 'Select from list' and choose WGS84 (G1762) current
• This should at least align everything
• 

I'm guessing you were formerly a Terrasync user on the Geo7x? 
If yes then have you looked at Trimble Terraflex (and the Trimble Terra Office ArcMap and ArcGIS Pro extension for ESRI users)?

I understand QGIS is free but If you are working to 1cm level you really need a professional system that handles geodetics and precise navigation with the highest level of accuracy and simplicity.
I'd recommend looking into Terraflex - there is a free 30 day trial available and migration tool to convert you existing Terrasync data dictionaries (or SSF) to a Terraflex project to speed up the process

Take a look at the Terraflex Skillbuilder series for quick start information and the online help HERE for more details

Hi,

The organisation I work for has historically used a Zephyr 2.0 receiver with a handheld Geo7x to both find and map points with 1cm accuracy. We specifically use these instruments for long-term agricultural field trials, some of which are over 100 years old, so accuracy is important and we need it to be within 1cm because this is also the tractor systems work to (also some of our trail plots are only 1m by 1m, so even 10cm can make a big difference).

With a lot of help from our IT team around software compatibility, the Zephyr/Geo7x system has worked really well for us over the last 10 years, but as they are now switching off the 3G network in the UK, we need to upgrade and have chosen to pair a Trimble DA2 receiver with a tablet that runs QGIS/QField. 

My problem is that I cannot get the two systems to find the same point location with 1cm accuracy. To test this we uploaded the same map (in WGS84) onto both systems and marked out several points using the old Zephyr/Geo7x. I then tried to navigate to these points using the DA2 and QField, but was consistently about 20cm out (see below photographs). I am almost certain there is a difference between the settings but I can't figure out what it is. Below is the device setup as I have figured it out on both systems so far. 

Any insight anyone has would be hugely appreciated. 

Hi Tom,

Thank you so much Tom. I'll go out into the field later this week and try what you suggested. I'll update this post with an answer once I've done the testing. 

We were using Terrasync, so thank you for the info on Terraflex.

Hi Aislinn

This looks like a datum shift error which should be easily fixed

If your GNSS output in TMM = Auto in the UK, then this will be using the OSNetv2009 (2009.76) datum, BUT your data and QGIS If understand correctly are using WGS84

This will add a shift in decimetres (depending on where you are in the UK) between your GNSS position and the data. 20cm sounds about right

In TMM try this

• Under the GNSS Configuration menu
• Change your GNSS OUTPUT to 'Select from list' and choose WGS84 (G1762) current
• This should at least align everything
• 

I'm guessing you were formerly a Terrasync user on the Geo7x? 
If yes then have you looked at Trimble Terraflex (and the Trimble Terra Office ArcMap and ArcGIS Pro extension for ESRI users)?

I understand QGIS is free but If you are working to 1cm level you really need a professional system that handles geodetics and precise navigation with the highest level of accuracy and simplicity.
I'd recommend looking into Terraflex - there is a free 30 day trial available and migration tool to convert you existing Terrasync data dictionaries (or SSF) to a Terraflex project to speed up the process

Take a look at the Terraflex Skillbuilder series for quick start information and the online help HERE for more details

Hi,

The organisation I work for has historically used a Zephyr 2.0 receiver with a handheld Geo7x to both find and map points with 1cm accuracy. We specifically use these instruments for long-term agricultural field trials, some of which are over 100 years old, so accuracy is important and we need it to be within 1cm because this is also the tractor systems work to (also some of our trail plots are only 1m by 1m, so even 10cm can make a big difference).

With a lot of help from our IT team around software compatibility, the Zephyr/Geo7x system has worked really well for us over the last 10 years, but as they are now switching off the 3G network in the UK, we need to upgrade and have chosen to pair a Trimble DA2 receiver with a tablet that runs QGIS/QField. 

My problem is that I cannot get the two systems to find the same point location with 1cm accuracy. To test this we uploaded the same map (in WGS84) onto both systems and marked out several points using the old Zephyr/Geo7x. I then tried to navigate to these points using the DA2 and QField, but was consistently about 20cm out (see below photographs). I am almost certain there is a difference between the settings but I can't figure out what it is. Below is the device setup as I have figured it out on both systems so far. 

Any insight anyone has would be hugely appreciated. 

Hi Aislinn,

As a general comment I would avoid using WGS84 and particularly if you are looking for cm accuracy. A one-of test between two devices at the same time might be ok as it's only a relative comparison, but as you have seen even that can still open you to other issues.

For your data it's definitely not good, WGS84 coordinates are space based and not fixed to the ground. And that ground that you and your points are on is surfing through space, in the UK around 2.5cm every year. So anything you record in WGS84 will never be at the same coordinates on the ground when you go back, and the amount of error will depend on how long it's been. For example, after the hundred years you mention those points would be 2.5 metres away.

I would standardize to your national datum for everything, including testing as that way you will know everything is set up right and in sync.

Cheers

Hi Tom,

Thank you so much Tom. I'll go out into the field later this week and try what you suggested. I'll update this post with an answer once I've done the testing. 

We were using Terrasync, so thank you for the info on Terraflex.

Hi Aislinn

This looks like a datum shift error which should be easily fixed

If your GNSS output in TMM = Auto in the UK, then this will be using the OSNetv2009 (2009.76) datum, BUT your data and QGIS If understand correctly are using WGS84

This will add a shift in decimetres (depending on where you are in the UK) between your GNSS position and the data. 20cm sounds about right

In TMM try this

• Under the GNSS Configuration menu
• Change your GNSS OUTPUT to 'Select from list' and choose WGS84 (G1762) current
• This should at least align everything
• 

I'm guessing you were formerly a Terrasync user on the Geo7x? 
If yes then have you looked at Trimble Terraflex (and the Trimble Terra Office ArcMap and ArcGIS Pro extension for ESRI users)?

I understand QGIS is free but If you are working to 1cm level you really need a professional system that handles geodetics and precise navigation with the highest level of accuracy and simplicity.
I'd recommend looking into Terraflex - there is a free 30 day trial available and migration tool to convert you existing Terrasync data dictionaries (or SSF) to a Terraflex project to speed up the process

Take a look at the Terraflex Skillbuilder series for quick start information and the online help HERE for more details

Hi,

The organisation I work for has historically used a Zephyr 2.0 receiver with a handheld Geo7x to both find and map points with 1cm accuracy. We specifically use these instruments for long-term agricultural field trials, some of which are over 100 years old, so accuracy is important and we need it to be within 1cm because this is also the tractor systems work to (also some of our trail plots are only 1m by 1m, so even 10cm can make a big difference).

With a lot of help from our IT team around software compatibility, the Zephyr/Geo7x system has worked really well for us over the last 10 years, but as they are now switching off the 3G network in the UK, we need to upgrade and have chosen to pair a Trimble DA2 receiver with a tablet that runs QGIS/QField. 

My problem is that I cannot get the two systems to find the same point location with 1cm accuracy. To test this we uploaded the same map (in WGS84) onto both systems and marked out several points using the old Zephyr/Geo7x. I then tried to navigate to these points using the DA2 and QField, but was consistently about 20cm out (see below photographs). I am almost certain there is a difference between the settings but I can't figure out what it is. Below is the device setup as I have figured it out on both systems so far. 

Any insight anyone has would be hugely appreciated.