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Datum
In geology, geography, cartography, surveying and other disciplines, a datum is a reference surface against which measurements can be made. Datum is also the singular for data.
For instance, sea-level is commonly used as a datum against which height (or depth) of topographic features can be measured. Whilst the use of sea-level as a datum is useful for geologically recent topographic features, it should be remembered that sea-level has not stayed constant throughout geological time (see Vail-curve).
On maps, heights and depths will typically be given in height above datum or depth below datum. Ordnance Survey maps define the Ordnance Survey Datum or OSD which is usually sea-level, but should be checked in the map legend.
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Datum
Anonymous - January 9th, 2006
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datum in machinist term
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Datum
www.resumeninja@yahoo.com - August 13th, 2006
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hello. I'm the only girl in my class and i dont want to ask the guys for help, so i'm asking you. If you can explain to me how to make the calculations for this question, i would really appreciate it. (part one) Describe the use of profile boards and travellers to control the excavation, by hydraulic backactor, for a typical drain run of about two meters deep and 1 meter wide. (Part two) Carry out the calculations, clearly stating any assumptions made, required to establish such a control system for a drain run with the following details: drain run
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