Surveying at heights close to sea level results in an incorrect field surface.

Symptoms:

The collected field elevation map (in T3RRA software) appears vastly different from your expectation of what the actual field looks like. You are surveying a field where elevations can be both negative and positive (i.e., partially above and partially below sea level). When you examine your field map you see that all elevation values are either negative or positive (not both). You are using a StarFire 3000 receiver and receiving serial data directly from the receiver (not via iGrade).

Cause:

The StarFire 3000 has a bug that causes problems with output elevations when it crosses between positive and negative elevation values.

Solution:

1. Alter your base station height so that the whole field can be surveyed using elevations that are either all positive or all negative.
2. Use iGrade and an implement receiver to survey the field.