Datum is an imaginary vertical plane from which all horizontal measurements are taken with the aircraft in a level flight attitude.
A dimension that exactly locates a reference point, reference line, or reference plane
It is entirely up to the manufacturer of the aircraft. Usually it is an imaginary point forward of the nose of the aircraft and all points aft of that datum have a positive value. This makes weight and balance calculations easier as there are no negative numbers.
It is a fixed reference point whose elevation above a given datum line
The datum location of a Cessna 172F is typically located at the leading edge of the wing, specifically at the wing's root. This reference point is used for weight and balance calculations to ensure the aircraft is within its center of gravity limits for safe operation. Properly identifying and utilizing the datum is crucial for maintaining the aircraft's performance and stability during flight.
Land-surface datum is a datum plane that is approximately at land surface at each well. If known, the elevation of the land-surface datum above sea level is given... Datum: any level surface, line, or point used as a reference in measuring elevations.
To select a suitable datum, consider a stable reference point on the workpiece or surface. Mark the datum clearly and securely. When marking out, ensure all measurements and reference points are taken from this datum to maintain accuracy and consistency. Working from a different datum can lead to incorrect measurements, misalignments, and errors in the final product. It is crucial to avoid this by consistently using the established datum.
When utilizing the DAGR, the field that automatically displays the waypoint datum is the "Dat" field, which stands for datum. The datum represents the reference point used to define the location coordinates of the waypoint.
Hydraulic grade line is sum of Datum + Pressure Head Energy grade line is sum of Datum + Pressure Head + Velocity Head
The horizontal datum used by GPS is the World Geodetic System 1984 (WGS 84). It provides a consistent reference frame for defining positions on the Earth's surface.
Aircraft manufacturers select the datum line based on factors like ease of measurement, structural design, and the aircraft's intended use. It is typically positioned in front of the nose to facilitate accurate weight and balance calculations, ensuring that the center of gravity can be effectively managed during various flight conditions. This location simplifies the alignment with other critical reference points, enhancing overall stability and performance during design and operation.
Fuselage stations are normally referenced from a reference datum which some distance forward of the first fuselage component. The reference datum normally relates to a precisely defined point on the manufacturers jig. Nominating a datum forward of the first airframe component allows for some flexibility in any redesign of the nose. Also the reference datum has to be off the airframe because the dimensions of the airframe itself will vary with temperature - unlike the jig on which it is made
A land survey datum (plural datums) is a reference from which measurements are made. The reference in the form of a set of coodinate and a direction. The datum can be arbitary (assumed) or absolute. The arbitary datum point is a point whose coordinate and direction are not known, so an arbitary value is adopted. All other coodinates of the survey project are connected together, but its datum point is not connected to a larger network. The absolute datum is a reference point whose coordinate and direction are already known within a frame of network. So the new survey become part of the network.