Datum

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Frequently Asked Questions

• How are datum features shown on a drawing?

  How Datum Features are Shown on a Drawing The Datum features on a drawing are denoted with a series of capital letters. These letters are in boxes and tied to the Datum feature with a black triangle. This letter will also show up in any feature control frame that uses this Datum feature as a reference.

• Can a datum be simulated by measurement equipment?

  Datums are theoretical and only simulated by Measurement Equipment (Gauge pins, Granite slabs, angle plates, computer generated planes, etc) Datum Features are real, tangible features on a part where the measurement equipment would physically touch or measure.

• What is the definition of a datum in GD & T?

  Definition: A Datum is theoretical exact plane, axis or point location that GD&T or dimensional tolerances are referenced to. You can think of them as an anchor for the entire part; where the other features are referenced from. A Datum feature is usually an important functional feature that needs to be controlled during measurement as well.

• Who is the inventor of the datum reference frame?

  In GD&T this is called Datum Reference Frame whereas in mathematics it is the Cartesian coordinate system invented by Rene Descartes in France (1596-1650). Often one would express this concept as the need to establish the X,Y, and Z coordinates.

• Who is datum systems and what do they do?

  Datum Systems, Inc. designs and manufactures satellite communications ground equipment. We specialize in high performance satellite modems for SCPC and VSAT applications. Datum Systems uses sophisticated designs to provide customers with a combination of quality, state of the art performance and the lowest cost modem in the industry.

• What kind of satellite modem does datum systems use?

  We specialize in high performance satellite modems for SCPC and VSAT applications. Datum Systems uses sophisticated designs to provide customers with a combination of quality, state of the art performance and the lowest cost modem in the industry.

• Why do we need a common survey datum?

  Universally accepted common survey Datums are essential for the efficient sharing of engineering and geospatial data for developing and operating a modern transportation system. A geodetic Datum is an abstract coordinate system with a reference surface (such as an ellipsoid) that serves to provide known locations to begin surveys and create maps.

• Which is the best description of a geodetic datum?

  According to NGS, a geodetic Datum is “A set of constants specifying the coordinate system used for geodetic control…” A geometric Datum, such as NAD 83, “has no direct dependence on the gravity field of the earth”.