Purpose

This article explains how Reference Elevation works in FieldLink, when it should be used, and how it differs from a Site Calibration.

When to Use Reference Elevation

Reference Elevation is intended for stub-up layouts or other workflows that require a flat elevation plane.

For most GNSS layout, Site Calibration should be used instead, as it provides true elevations based on the project's control points.

How Reference Elevation Works

When you select Reference Elevation, FieldLink prompts you to occupy a known point with a known elevation. Once entered, FieldLink establishes a flat elevation plane using that point as the reference.

All subsequent elevation measurements are calculated relative to this reference plane rather than the project's Site Calibration.

Example:

• Reference Elevation = 2.00 ft
• Move up 4.00 ft

Displayed Elevation = 6.00 ft

Importance of Rod Height

Before performing a Reference Elevation, verify that the rod height in FieldLink is correct.

This is especially important if you're using:

• A rod extension
• A quick release
• Any accessory that changes the antenna height

FieldLink uses the rod height to calculate the elevation of the ground point from the GNSS antenna position.

If the rod height is incorrect, the Reference Elevation will also be incorrect, and every elevation measured from that reference will contain the same error.

Example:

• Actual rod height: 6.50 ft
• Rod height entered in FieldLink: 6.00 ft

Every elevation will be 0.50 ft off because the incorrect rod height was used when establishing the reference.

Using Reference Elevation

Reference Elevation can also be useful when working with an RTS or GNSS to quickly verify elevations.

1. Occupy a known point.
2. Perform a Reference Elevation using the known elevation.
3. Move to another location.
4. View the current elevation in Device Settings.

This allows you to check the elevation of locations relative to the reference point without relying on the project Site Calibration.

Note: These elevations are relative to the established Reference Elevation and are not the true surveyed elevations from the Site Calibration.

Reference Elevation vs. Site Calibration

Best Practices

• Use Site Calibration for standard GNSS layout.
• Use Reference Elevation only when a flat reference plane is required.
• Always verify the rod height before establishing a Reference Elevation.
• If elevations appear consistently offset by the same amount, verify the rod height first.