# Vertical adjustment

If published datum transformation parameters are used, slight discrepancies can exist between local control and GNSS‑derived coordinates. These discrepancies can be reduced using minor adjustments. Trimble Access calculates these adjustments when you use the Site calibration function, if the coordinate system settings for the job include a projection and a datum transformation. They are called horizontal and vertical adjustments.

If required, you can use a geoid model file as part of the vertical adjustment calculation.

You can reuse the calibration from a previous job if the new job is completely encompassed by the initial calibration. If a portion of the new job lies outside the initial project area, introduce additional control points to cover the unknown area. Survey these new points and compute a new calibration, and then use this as the calibration for the job.

To copy the calibration from an existing job to a new job, select the existing job as the current job and then create a new job and in the Template field select Last used job. Alternatively, use the Copy between jobs function to copy the calibration from one job to another.