Best Practices: Project Base Point and Survey Point

Consider these strategies to optimize your use of the project base point and the survey point.

• Experiment using a sample model.
• Check the model's distance from the internal origin.
• Position an imported DWG site.
• Prepare to export a building site to an ADSK file.

For details on these strategies, read the following sections.

Experiment using a sample model

The best way to understand how the project base point and the survey point work is to experiment with them. Download this sample model to play with. It contains spot coordinates based on survey points (black) and project base points (orange).

In the model, open the site plan view, and try the following:

• Rotate True North.
• Move the project base point when it is clipped, and again when it is unclipped.

  Also try moving the project base point back to the startup location (the internal origin).

• Move the survey point when it is clipped, and again when it is unclipped.

In each case, notice the following:

• Which spot coordinates change?

  Remember: the black spot coordinates are relative to the survey point, and the orange spot coordinates are relative to the project base point.

• Does the change affect Project North? or True North?
• Does the survey coordinate system or the project coordinate system move in relation to the model?

This type of hands-on experimentation is one of the best ways to understand these important positioning mechanisms.

Check the model's distance from the internal origin

To ensure accuracy of the model, the model geometry must be less than 32 kilometers or 20 miles from the startup location of the project base point (the internal origin). To check this measurement, do the following:

1. Select the project base point and unclip it.
2. Right-click the project base point, and click Move to Startup Location.
3. To measure the distance from the project base point to the model geometry, use the Measure tool on the Modify tab.
4. If the distance exceeds the maximum, move the model geometry within 32 kilometers or 20 miles of the startup location of the project base point.
5. Unclip the project base point and move it back to the desired location.

Position an imported DWG site

If a civil engineer provides a DWG file that contains site information for your model, do the following to ensure that the DWG file is positioned correctly:

1. Define the survey point using the coordinates from the civil engineer.
2. Rotate True North to specify the correct angle in relation to the model.
3. Import or link the DWG file.

   When linking the DWG file, for Positioning, specify Auto - By Shared Coordinates.

Prepare to export a building site to an ADSK file

Before exporting a building site to a civil engineering application that accepts ADSK files, such as AutoCAD Civil 3D, do the following:

1. Move the unclipped survey point to the location agreed upon with the civil engineer.
2. Use the Specify Coordinates at a Point tool or enter the coordinates on the Site tab of the Building Site Export dialog, using the coordinates provided by the civil engineer.

Then export the building site to an ADSK file.