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Davis quadrants (quadrants (measuring devices), vertical angle measuring devices, ... Furnishings and Equipment (hierarchy name)) |
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Note: Navigational instruments designed by the Englishman John Davis in 1594. This instrument measures the height of the sun by the projection of a shadow. In this case the observer stands with their back to the sun, hence the English name 'backstaff'. Instead of the cross of the Jacob's staff, the Davis quadrant features two arcs to which sliding vanes are mounted. By taking the horizon as the starting point, the observer can measure the shadow of the vane on the first arc using that of the second arc. The Davis quadrant was originally made of wood with ebony or ivory quadrants.Brass or steel predominanted after about 1775.
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| Terms: |
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| Davis quadrants (preferred,C,U,English-P,D,U,PN)
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| Davis quadrant (C,U,English,AD,U,SN)
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| backstaff (C,U,English,AD,U,SN)
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| backstaffs (C,U,English,UF,U,U)
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| daviskwadranten (C,U,Dutch-P,D,U,U)
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| daviskwadrant (C,U,Dutch,AD,U,U)
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| quartier de davis (C,U,French-P,AD,U,MSN)
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Facet/Hierarchy Code: V.TN |
Hierarchical Position:
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Objects Facet |
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.... Furnishings and Equipment (hierarchy name) (G) |
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........ Measuring Devices (hierarchy name) (G) |
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............ measuring devices (instruments) (G) |
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................ <measuring devices for extent> (G) |
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.................... distance measuring devices (G) |
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........................ angle measuring devices (G) |
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............................ vertical angle measuring devices (G) |
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................................ quadrants (measuring devices) (G) |
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.................................... Davis quadrants (P,U) |
Additional Notes: |
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| Dutch ..... Verbeterde uitvoering van de jacobsstaf, ontworpen door de Engelsman John Davis in 1594. Bij dit instrument is uitgegaan van het meten van de lengte van de slagschaduw waaruit de hoogte van de zon kan worden afgeleid. De waarnemer komt in dit geval met de rug naar de zon te staan, wat het instrument de Engelse naam ‘back staffâ bezorgde. In plaats van het kruishout van de jacobsstaf is de daviskwadrant voorzien van een tweetal bogen waarop verschuifbare vizieren zijn aangebracht. Door ook hier weer de horizon als uitgangspunt te kiezen kan de waarnemer de schaduw van het vizier op de eerste boog meten met die van de tweede. Het daviskwadrant is oorspronkelijk uit hout met ebbenhouten of ivoren graadbogen. Na ca. 1775 wordt overwegend messing of staal gekozen. |
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Sources and Contributors: |
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| backstaff............ |
[AASLH Preferred, CHIN / RCIP Preferred, RKD, AAT-Ned] |
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AASLH data (2016-) |
| .................... |
Bennett, Jim, "Catadioptrics and commerce in eighteenth-century London", in History of Science, vol xliv, 2006, pages 247â277. |
| .................... |
CHIN / RCIP translation (2016-) |
| .................... |
Nomenclature database (2018-) http://nomenclature.info/nom/10103; scheme: Nomenclature-Objects |
| .................... |
Nomenclature for Museum Cataloging / Nomenclature pour le catalogage translation project (2016-) 10103 |
| .................... |
Royal Museums Greenwich, Collections [online] (2017-) |
| Davis quadrants............ |
[RKD, AAT-Ned Preferred, VP Preferred] |
| ............................. |
Bennett, Jim, "Catadioptrics and commerce in eighteenth-century London", in History of Science, vol xliv, 2006, pages 247–277. |
| ............................. |
Robinson, Sailing Ships of New England 1607-1907 (2014) |
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Royal Museums Greenwich, Collections [online] (2017-) NAV0036 |
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Subject: ..... |
[AASLH, CHIN / RCIP, RKD, AAT-Ned, VP] |
| ............ |
AASLH data (2016-) |
| ............ |
CHIN / RCIP translation (2016-) |
| ............ |
Nomenclature database (2018-) http://nomenclature.info/nom/10103; scheme: Nomenclature-Objects |
| ............ |
Nomenclature for Museum Cataloging / Nomenclature pour le catalogage translation project (2016-) |
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| Note: |
| English | .......... | [RKD, AAT-Ned, VP] |
| .......... | Bennett, Jim, "Catadioptrics and commerce in eighteenth-century London", in History of Science, vol xliv, 2006, pages 247â277. |
| .......... | Royal Museums Greenwich, Collections [online] (2017-) |
| Dutch | .......... | [RKD, AAT-Ned] |
| .......... | Antiek-Encyclopedie |
| .......... | Mardoc |
| .......... | Maritiem Digitaal |
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