Finals (Terms) (Height System)

48問 • 8ヶ月前

問題一覧

Where does the appropriate definition of height sourced from?

National Geodetic Survey Glossary

that distance, measured upwards along a plumb line (line of force), between a point and a reference surface of constant geopotential.

Height

the arithmetic mean of hourly heights recorded from a tide gauge for a specific 19-year Metonic cycle

MSL

the _____ is established by tying it to the MSL

geoid

The determinationof the MSL involves the installationof tide gauges at suitable places and taking one of them orthe mean of several of them as the ________

location of the geoid

Tide gauge inside the bays influenced by ____and ____ factors may not give the true level

geophysical, local

reference value for MSL is defined at a specific ____.

epoch

heights above MSL are carried out landward by means of __________ or _______

differential levelling, trigonometric levelling

What causes the misclose of a geometric leveling measured even at utmost precision?

non parallelism of the equipotential surfaces

uncorrected leveling heights as ______ valued, which means that the result is ______ on the path taken

not single, dependent

Heights from _________ leveling can only be physically meaningful if combined with _______ measurement.

differential, gravity

are from a reference ellipsoid

Ellipsoidal Height

referenced to the Earth’s gravity field

Geopotential Height

Measuring the heights from the local spheroid/ ellipsoid is quite a daunting task because it requires determination of the ______ of the _____ derived from _____ and _______ measurements

deflection, vertical, gravity, astronomical

Heights derived from this method are normal to the surface of the said ellipsoid.

Geocentric ellipsoid height

This type of height is a geometric quantity

Geocentric ellipsoid heights

Geopotential Heights and their Symbols or letters

Geopotential Number - C, Dynamic Height - H^dyn, Orthometric Height - H, Normal Height - H^N, Normal-Orthometric Height - H^N-O

potential difference between the potential of a point of interest and the potential of a point at the reference surface

Geopotential Number

1 GPU = _ kgal

____ cm²s^-2 = ____ m²s^-2

100,000, 10

Which one is true?

The significance of the geopotential number is that water will not flow between points if the numbers are the same

inconvenience of height unit given in GPU or kgal-meter of a geopotential number can be resolve by dividing it by a gravity value to convert it to meter.

Dynamic Height

Y↓45 = ___ gal

980.6294

What geopotential height is a physical quantity rather than geometric quantity?

Dynamic Height

Reason for unpopular use of dynamic height

correction result in large value

Where does dynamic height be used?

when water level is needed

Country that adopted dynamic height

Canada

Heights from precise leveling can be converted to dynamic heights by applying ____________

dynamic correction

Heights measured above the geoid

Orthometric Height

length of the plumbline (curved- line distance) from the geoid to the point of interest

Orthometric Height

mean gravity can be computed if the actual values of gravity between the ____ and the _____can be determined.

geoid, earth's surface

Normal height was introduced by ______ in ______ to avoid making assumptionsof the earth’ s crust.

Molodensky, 1945

Molodensky showed that the “ physical surface of the earth can be determined from _____ measurements alone, without using the _____ of the earth’ s crust

geodetic, density

The straight-line distance from the earth’ s surface and the telluroid is the _________

height anomaly

the normal height is extended downward from the earth’s surface it will yield the _______

quasigeoid

the normal height is extended ______ from the earth’s surface it will yield the quasigeoid

downward

height anomalies ζ are plotted above the ellipsoid this will also give the _______.

quasigeoid

the ______ height is the height above the quasigeoid the _____ height is the height above the geoid

normal, orthometric

Countries that adopt normal height

France, Sweden, Germany

The normal-orthometric height is similar to the normal heights except that the height anomaly ζ becomes the separation of the ______ and the _______

reference ellipsoid, quasigeoid

the distance from the quasigeiod to the point P on the earth’s surface along the normal plumbline.

normal-orthometric height

Country that adapted normal orthometric

Australia

reference surface of normal orthometric height

Quasigeoid

the direct result of leveling and is of great scientific importance

Geopotential Number

natural “heights above sea level”, that is heights above the geoid.

Orthometric Height

In the ___ leveling line of ___ (____), leading from an elevation of ___ m to ___ m, the orthometric correction is about __ cm per_ km of measured differences.

Alpine, Mader, 1954, 754, 2505, 15, 1

one of the most accurate geodetic measurements.

Leveling

Desired requirements of height system

Misclosures be eliminated, Corrections to the measured heights be as small as possible

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