Catalog Pricing FAQ HoursDemo accessJordan Hale, PLS

What are Geodetic Datums?

usoceangov · 4 min · 0.05 CE hr

Completed

GPS/GNSSStandards

NOAA/NOS explainer of what a geodetic datum is, why NAD 27 and NAD 83 are not interchangeable, and why the datum must be stated with coordinates.

Watch progress100%

Quiz unlocks at 80% watched, or when the player reports the video ended. Progress is saved to your account.

Loading YouTube player…

Module quiz

This module is complete. You may retake the quiz; hours are credited once per year.

1. In this explainer, what is a geodetic datum?

A brand of GNSS receiverA reference framework (origin, orientation, and ellipsoid) used to compute positions on the EarthA county GIS parcel layerA magnetic declination table

2. Why must you name the datum when you report latitude/longitude or grid coordinates?

Datums are only a paperwork formalityThe same numeric coordinates can refer to different ground positions on different datumsNAD 27 and NAD 83 occupy exactly the same pointsCourts prohibit mixing bearings and coordinates

3. Which pair of horizontal datums does the video treat as the modern U.S. succession?

WGS 72 and ED50NAD 27 and NAD 83NGVD 29 onlyOSGB36 and ETRS89

4. What is a practical field takeaway for surveyors?

You can mix NAD 27 plat ties and NAD 83 GNSS shots without a transformationControl, plats, and GNSS must be on a stated, consistent datum (or properly transformed) before you hold them togetherDatums only matter for hydrographic surveysA handheld mapping-grade phone always matches the plat datum

TraverseCE documents watch-verified module hours. Not a board-approved provider. Confirm acceptance with your state board.

Catalog Pricing FAQ