A datum line is a reference line used to control height and horizontal distance measurements. It can be a plane, a straight line, or a point. It is established using datum features and simulated datum features. The Geospatial Glossary defines horizontal datums as a series of data points on the Earth's surface used to measure the position of oneself on the Earth's surface.<br />...<br /><a href="https://www.youtube.com/watch?v=xkGDnuiJ8yQ" target="_blank" rel="nofollow">https://www.youtube.com/watch?v=xkGDnuiJ8yQ</a>