Trimble Business Center

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

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GUY BIEN
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Check to see that you have the right  coordinate system and zone selected. Also check the that local control you have tied into has appropriate grid coordinates for the coordinate system and zone.  In TBC under Project Settings, View, Point Spreadsheet, if you turn on the combined sale factor, you should be able to see what sort of scale factor is being applied to each point in the job. To get a error of 6 feet over 550 meters to scale factor would need to be substantial.
If you can post the job here and I will take a look at it.

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James McWha
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Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

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GUY BIEN
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I have specific values for example.  Inverse between pts 2000 to 2070.  Access HD=594.68',  TBC HD=599.65', Optical measured HD=599.65.  Inverse between pts 2000 to 2072.  Access HD=277.60',  TBC HD=279.92', Optical measured HD=279.92.  This indicates to me Access is applying some sort of scale factor.  

The file would not upload.  Will email.

Thanks for having a look.

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GUY BIEN
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Original Message:
Sent: 10-27-2021 19:04
From: James McWha
Subject: Using conventional surveying with GPS surveys on a calibrated site

Check to see that you have the right  coordinate system and zone selected. Also check the that local control you have tied into has appropriate grid coordinates for the coordinate system and zone.  In TBC under Project Settings, View, Point Spreadsheet, if you turn on the combined sale factor, you should be able to see what sort of scale factor is being applied to each point in the job. To get a error of 6 feet over 550 meters to scale factor would need to be substantial.
If you can post the job here and I will take a look at it.

------------------------------
James McWha

Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

------------------------------
GUY BIEN
------------------------------

Original Message:
Sent: 10/27/2021 10:04:00 PM
From: James McWha
Subject: RE: Using conventional surveying with GPS surveys on a calibrated site

Check to see that you have the right  coordinate system and zone selected. Also check the that local control you have tied into has appropriate grid coordinates for the coordinate system and zone.  In TBC under Project Settings, View, Point Spreadsheet, if you turn on the combined sale factor, you should be able to see what sort of scale factor is being applied to each point in the job. To get a error of 6 feet over 550 meters to scale factor would need to be substantial.
If you can post the job here and I will take a look at it.

------------------------------
James McWha
------------------------------

Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

------------------------------
GUY BIEN
------------------------------

Typically when I get differences of 3 or more feet it has to do with US Survey Feet vs International Feet.   Make sure Access and your CAD program are set to the appropriate foot.  If you are using Civil 3D, make sure the drawing settings and the survey module settings are set to the same foot definition.  ​

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Charlie Wagner
------------------------------

Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

------------------------------
GUY BIEN
------------------------------

Thank you for the suggestion.  All the settings are at US survey feet.

------------------------------
GUY BIEN
------------------------------

Original Message:
Sent: 10-28-2021 07:12
From: Charlie Wagner
Subject: Using conventional surveying with GPS surveys on a calibrated site

Typically when I get differences of 3 or more feet it has to do with US Survey Feet vs International Feet.   Make sure Access and your CAD program are set to the appropriate foot.  If you are using Civil 3D, make sure the drawing settings and the survey module settings are set to the same foot definition.  ​

------------------------------
Charlie Wagner

Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

------------------------------
GUY BIEN
------------------------------

to me it sounds like a problem with either the coordinate system in access or more likely the site calibration that you performed.

when you bring into tbc do you keep the site calibration on import or tell tbc to use the coordinate system it has from the existing project or template? if you null the calibration and then use what tbc is using then pass that along to survey pro and it works, then this seems to be the correct coordinate system you need.

another question. this might get a lot of people upset, but i don t see why you would perform a site calibration. to me, any error in your observations on that particular day (could be .02m rtk) will be applied to the calibration. this is fine for a topo, but for other precise work is not optimal. 

there are other ways to 'calibrate' your site. if your goal is to work in a ground system you can in access go to: properties/coordinate system/select from library/coordinates drop down choose ground. click the point button in the lower options. then you can enter the scale factor or choose the calc scale factor that access will compute from the point. this is all similar to the projection option in survey pro.

hopefully this helps a little. if you explain a bit more what your goals are then maybe i would have more suggestions. good luck

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ian bissonnette
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Original Message:
Sent: 10-28-2021 08:59
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

Thank you for the suggestion.  All the settings are at US survey feet.

------------------------------
GUY BIEN

Original Message:
Sent: 10-28-2021 07:12
From: Charlie Wagner
Subject: Using conventional surveying with GPS surveys on a calibrated site

Typically when I get differences of 3 or more feet it has to do with US Survey Feet vs International Feet.   Make sure Access and your CAD program are set to the appropriate foot.  If you are using Civil 3D, make sure the drawing settings and the survey module settings are set to the same foot definition.  ​

------------------------------
Charlie Wagner

Original Message:
Sent: 10-27-2021 07:49
From: GUY BIEN
Subject: Using conventional surveying with GPS surveys on a calibrated site

I am having an issue with using conventional survey equipment with my GPS calibrated site with in Access.  My base station is set up on an OPUS derived benchmark.   I then calibrate the site to our known control.  From there I topo site and set additional control points to use with my conventional survey equipment for areas in which I cannot get a good GPS signal.  This is where the problem starts.  When I perform station setup and check my back site distance it comes up short by a large amount.  2.7 feet over 290 feet and 6 feet over 550 feet.  However, when I drop the .job file in TBC and export points to an .asc and upload to Survey Pro and use my conventional equipment it checks to 0.01 feet.  It seems to me there is a scale factor creating the error when I transfer to the conventional use within Access, but I have no idea where is might be or if my initial .job setup is the issue.  Any help would be greatly appreciated.

------------------------------
GUY BIEN
------------------------------