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Calibrating Data

 

 

 

 

Starting with TPC Desktop 2019, TPC allows you to calibrate survey data and drawing objects to your survey's Coordinate Reference System (CRS).

Learning Calibrations


What is a Calibration?

A calibration is a 2D or 3D coordinate transformation which rotates, translates and scales positions in one coordinate system to match coordinates in another.

TPC supports 2D/3D Conformal, 2D/3D Affine and other classic coordinate transformations. See Calibration Types.

Depending on what you are calibrating, TPC will either select the appropriate calibration type for you, or allow you to select it.


Calibration Examples

Here are just a few examples of calibrations

Calibrate data from a CAD drawing in inches to your survey in feet

Calibrating coordinates from grid to ground

Automatically calibrate geodetic points onto your local site (ground distances at 5000/5000)

Calibrate total station data based on assumed coordinates to match your survey’s control points

Reference an imported raster image to your survey as a background image


Coordinate Systems

When describing calibrations, TPC uses the term coordinate system.

If you are calibrating a CAD XRef to your survey, the coordinates in the XRef will change from the coordinate system used by the CAD file to your survey's coordinate system.

If you are calibrating ground data to your survey's CRS (Coordinate Reference System), the coordinates will no longer be ground coordinates, but will instead be CRS (grid) coordinates.


Calibrating Survey Data

You calibrate survey data like points and traverses with the Calibrate and Uncalibrate commands.

Once calibrated, survey data objects like points and lines know that they have been calibrated and by which calibration. So they are now free to display and use their calibrated positions. They can still report their uncalibrated positions and if need be, their calibration can be reversed, reverting them back to their original, uncalibrated data.

See Calibrating Survey Data.


Site Calibration

A Site Calibration is a single calibration you apply to the survey in the Survey Information's Site Calibration dialog. The Site Calibration automatically calibrates certain data. 

An example would be to calibrate imported GPS / GNSS data to a local site. 

The geodetic LLh positions would compute corresponding coordinates YXZ based on the survey's CRS (Coordinate Reference System). 

The site calibration would then automatically calibrate them to local site coordinates yxz.

Likewise, when exporting local site coordinates to GPS / GNSS, the site calibration would automatically compute their CRS coordinates YXZ which would then be converted to the appropriate geodetic positions LLh.


Calibrating Drawing Data

You can calibrate drawing objects to your survey or to each other.

Once calibrated, drawing objects like lines, polylines and rectangles know that they have been calibrated and by which calibration. So they are now free to display and use their calibrated positions. They can still report their uncalibrated positions and if need be, their calibration can be reversed, reverting them back to their original, uncalibrated data.

You can also select an existing calibration when exporting a drawing to a CAD file, like DWG or DGN. You will probably want to reverse the calibration to get the desired results in the CAD file.

See Calibrating Drawing Data.


Survey Calibrations

A survey can use any number of calibrations. Once you use a calibration, it is automatically added to the survey.

As you create calibration, TPC adds  information about that calibration to the survey's TRV file for future reference and to help manage the calibration index stored with the survey's data and drawing objects.  If you move a survey file to another folder, this calibration information is still available to the survey. This maintains the integrity of the calibration, allowing you to uncalibrate and recalibrate as needed.

You can manage a survey's calibrations in the Manage Survey Calibrations dialog.


Calibration Associations

When you calibrate data from a file, like an imported DWG CAD file, TPC associates that calibration with that file. If you open that CAD file in TPC's CAD View, TPC will automatically calibrate data you share between the CAD View and the Drawing View. You can also reuse calibrations when you re-import that same file. 

See Calibration Associations and Calibration File References.


Related Topics

Calibrate Survey Command
UnCalibrate Survey Command
Calibrate Survey Dialog
UnCalibrate Survey Dialog
Drawing Data Manager
Drawing Data Manager Calibration Tools

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