How many datum targets are there?

How many datum targets are there?

A primary datum plane is established by a minimum of three datum targets not in a straight line. Two datum targets are used to establish a secondary datum plane. And one datum target establishes a tertiary datum plane. A combination of datum target points, lines, and areas may be used.

What is the most commonly used datum plane?

The North American Datum of 1983 (NAD 83) is the most current datum being used in North America. It provides latitude and longitude and some height information using the reference ellipsoid GRS80.

What are datum planes?

A datum plane is a plane on the target that is established as a datum. It can be a target’s external plane (datum plane) or center plane (datum center plane). “Datum plane” is defined as follows in ISO and ASME standards: A datum that is a theoretically exact plane.

What is the difference between a datum target and a datum feature?

The datum is an imaginary but theoretically perfect surface, line, or points. A datum feature, on the other hand, is the physical representation of datum. Datum targets are specified regions of the datum feature used for locating the part in a fixture.

What datum is Google Earth?

Google Maps and Microsoft Virtual Earth use a Mercator projection based on the World Geodetic System (WGS) 1984 geographic coordinate system (datum). This Mercator projection supports spheres only, unlike the ESRI Mercator implementation, which supports spheres and ellipsoids.

Why are there different datums?

Because there are different ways to fit the mathematical model to the surface of the Earth, there are many different datums. Also, in the modern digital era, techniques have vastly improved and many modern datum are very similar to each other.

What is a moveable datum target?

Movable datum targets are datum targets that are not fixed at their basic location, are free to translate, and can apply to a point, line, or area.

Where does a datum plane exist?

Datums exist within a structure of three mutually perpendicular intersecting planes known as a datum reference frame. A part is oriented and immobilized relative to the three mutually perpendicular planes of the datum reference frame in a selected order of precedence.

What is the datum plane aviation?

The reference datum is an imaginary vertical plane from which horizontal distances are measured for aircraft weight and balance purposes. The datum is determined by the manufacturer, and in small aircraft, the reference datum is often located along the firewall or at the leading edge of the wing.

What is a datum plane quizlet?

What is a datum? theoretical exact plane, axis or point location that dimensional tolerances are referenced to. a plane or axis, or point. they are measuring aspects of the actual geometry to assess how closely they match with the nominal value.

What is a datum target?

Datum Targets A datum target is a point, line, or limited zone on a target with which machines and instruments for processing, measuring, and inspection come into contact in order to establish a datum. The Need for Datum Targets Specifying a Datum Target

What are the different types of datum?

Major Types of Datum Features. 1 Datum Plane. A datum plane is a plane on the target that is established as a datum. It can be a target’s external plane (datum plane) or center plane 2 Datum Line. 3 Point. A datum point established on the center of a spherical target is indicated using the following symbol:

What is the difference between a datum and a plane?

A datum feature can be a plane, line, or point—these are selectively used depending on the tolerance and feature you need to specify. A datum plane is a plane on the target that is established as a datum. It can be a target’s external plane (datum plane) or center plane (datum center plane).

What is the 3-2-1 rule for primary datum?

It only applies when all three plaines are used. The 3-2-1 rule says: – The primary datum feature has at least 3 points of contact with its datum plane. – The secondary datum feature has at least 2 points of contact with its datum plane.