404:. Perhaps influenced by the backstaff, some navigators modified the cross-staff to operate more like the former. Vanes were added to the ends of the longest cross-piece and another to the end of the main staff. The instrument was reversed so that the shadow of the upper vane on the cross piece fell on the vane at the end of the staff. The navigator held the instrument so that he would view the horizon lined up with the lower vane and the vane at the end of the staff. By aligning the horizon with the shadow of the sun on the vane at the end of the staff, the elevation of the sun could be determined. This actually increased the accuracy of the instrument, as the navigator no longer had to position the end of the staff precisely on his cheek.
233:, he realized it had a sight with a graduated scale that could be used to measure the heights of distant mountains, likening it to how mathematicians measure heights by using right-angle triangles. He wrote that when one viewed the whole breadth of a mountain with it, the distance on the instrument was long; when viewing a small part of the mountainside, the distance was short; this, he wrote, was due to the cross piece that had to be pushed further away from the eye, while the graduation started from the further end. Needham does not mention any practical application of this observation.
326:
27:
377:
261:
35:
544:, the apparent and real thicknesses of beds diverge therefore making the use of a tape measure difficult. There is a certain level of error to be expected when using this tool, due to the lack of an exact reference mean for measuring stratigraphic thickness. High-precision designs include a laser able to slide vertically along the staff and to rotate on a plane parallel to bedding.
192:, in his "Book of the Wars of the Lord" (translated in Latin as well as Hebrew). He used a Hebrew name for the staff that translates to "Revealer of Profundities", while the term "Jacob's staff" was used by his Christian contemporaries. Its invention was likely due to fellow French-Jewish astronomer
414:
Ultimately, the cross-staff could not compete with the backstaff in many countries. In terms of handling, the backstaff was found to be more easy to use. However, it has been proven by several authors that in terms of accuracy, the cross-staff was superior to the backstaff. Backstaves were no
316:
The user places one end of the main staff against their cheek, just below the eye. By sighting the horizon at the end of the lower part of the transom (or through the hole in the brass fitting) , then adjusting the cross arm on the main arm until the sun is at the other end of the transom , the
364:
The cross-staff was difficult to use. In order to get consistent results, the observer had to position the end of the pole precisely against his cheek. He had to observe the horizon and a star in two different directions while not moving the instrument when he shifted his gaze from one to the
303:
It was common to provide several transoms, each with a different range of angles it would measure; three transoms were common. In later instruments, separate transoms were switched in favour of just one with pegs to indicate the ends. These pegs were mounted in one of several pairs of holes
470:- a drum or box shaped device mounted on a pole. It had two sets of mutually perpendicular sights. This device was used by surveyors to measure offsets. Sophisticated versions had a compass and spirit levels on the top. The French versions were frequently eight-sided rather than round.
133:, or the angle between the top and bottom of an object to determine the distance to said object if its height is known, or the height of the object if its distance is known, or the horizontal angle between two visible locations to determine one's point on a map.
66:. In its most basic form, a Jacob's staff is a stick or pole with length markings; most staffs are much more complicated than that, and usually contain a number of measurement and stabilization features. The two most frequent uses are:
439:, a single straight rod or staff made of nonferrous material, pointed and metal-clad at the bottom for penetrating the ground. It also has a screw base and occasionally a ball joint on the mount, and is used for supporting a
450:
may also have a different meaning in the history of surveying. While the astronomical cross-staff was used in surveying for measuring angles, two other devices referred to as a cross-staff were also employed.
184:
The original Jacob's staff was developed as a single pole device, in the 14th century, that was used in making astronomical measurements. It was first described by the French-Jewish mathematician
317:
altitude can be determined by reading the position of the cross arm on the scale on the main staff. This value was converted to an angular measurement by looking up the value in a table.
476:- an improved version of the cross-head, the optical square used two silvered mirrors at 45° to each other. This permitted the surveyor to see along both axes of the instrument at once.
365:
other. In addition, observations of the sun required the navigator to look directly at the sun. This could be a uncomfortable exercise and made it difficult to obtain an accurate
140:. With the demise of the cross-staff, in the modern era the name "Jacob's staff" is applied primarily to the device used to provide support for surveyor's instruments.
956:
Tests performed on various instruments are described. In addition, de
Hilster describes the handling characteristics found by the testers on the Nav List mailing list.
357:
introduced it to
England in the 1550s. In the improved versions, the rod was graduated directly in degrees. This variant of the instrument is not correctly termed a
200:
is less likely, because
Purbach was not born until 1423. (Such attributions may refer to a different instrument with the same name.) Its origins may be traced to the
517:
502:
497:
727:
105:
The simplest use of a Jacob's staff is to make qualitative judgements of the height and angle of an object relative to the user of the staff.
949:
408:
292:, slides up and down on the main staff. On older instruments, the ends of the transom were cut straight across. Newer instruments had
1110:
641:
935:
1100:
304:
symmetrically located on either side of the transom. This provided the same capability with fewer parts. The transom on
1095:
528:
Some devices, such as the modern optical targets for laser-based surveying, are still in common use on a Jacob's staff.
1076:
771:
1030:
997:
977:
813:
759:
627:
607:
366:
353:
suggested the cross-staff be used at sea in 1514 and improved instruments were introduced for use in navigation.
1115:
1054:
Patacci, M. (2016), A high-precision Jacob's staff with improved spatial accuracy and laser sighting capability
536:
In geology, the Jacob's staff is mainly used to measure stratigraphic thicknesses in the field, especially when
1125:
910:
512:
330:
1130:
1105:
248:
made improvements to this instrument. In the 15th century, the German mathematician
Johannes Müller (called
207:
Although it has become quite accepted that ben Gerson first described Jacob's staff, the
British Sinologist
972:, Nederlandsch Historisch Sheepvaart Museum, Amsterdam, and Walburg Instituut, Zutphen, Netherlands, 1994
229:
interested in ancient objects; after he unearthed an ancient crossbow-like device from a home's garden in
384:, above the sailor. This seal dates from 1915, though a cross-staff is depicted in 17th century versions.
193:
831:
Science and
Civilization in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth
168:. Another possible source is the Pilgrim's staff, the symbol of St James (Jacobus in Latin). The name
101:) for a vertical rod that penetrates or sits on the ground and supports a compass or other instrument.
857:
An
Analysis Of Navigational Instruments In The Age Of Exploration: 15th Century To Mid-17th Century
574:
416:
354:
277:
196:, who also lived in Provence in the same period. Attribution to 15th century Austrian astronomer
648:
This article indicates the three belt stars are sometimes called Jacob's Ladder or Jacob's Stick
946:
148:
The origin of the name of the instrument is not certain. Some refer to the
Biblical patriarch
1120:
844:
Wissenschaftliche
Instrumente in ihrer Zeit. Band 1: Vom Astrolab zum mathematischen Besteck.
393:
381:
161:
540:
is not visible or unclear (e.g., covered outcrop) and when due to the configuration of an
8:
397:
325:
26:
893:
731:
723:
685:
563:
480:
In the past, many surveyor's instruments were used on a Jacob's staff. These include:
338:
297:
668:
396:, neither of which required the user to stare directly into the sun, and later by the
136:
The Jacob's staff, when used for astronomical observations, was also referred to as a
1026:
993:
973:
931:
897:
809:
755:
735:
657:
638:
623:
603:
558:
221:
342:
928:
Scientific
Instruments of the Seventeenth and Eighteenth Centuries and Their Makers
885:
715:
1058:
728:
10.2979/aleph.11.2.365.pdf?refreqid=excelsior:a08ab1beb338a72c69a372d21cc1f553
1080:
953:
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185:
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121:
and was used to determine angles, for instance the angle between the horizon and
276:
In the original form of the cross-staff, the pole or main staff was marked with
507:
492:
300:, these fittings are often the only components of a cross-staff that survive.)
241:
208:
388:
As a navigational tool, this instrument was eventually replaced, first by the
157:
1089:
1073:
537:
376:
305:
249:
245:
197:
870:
775:
706:
Goldstein, Bernard (2011). "Levin ben Gerson and the Cross Staff Revisted".
889:
719:
370:
212:
568:
522:
487:
265:
252:) made the instrument popular in geodesic and astronomical measurements.
237:
226:
1055:
165:
114:
75:
970:
The Cross-staff, History and development of a navigational instrument
553:
428:
389:
173:
90:
71:
808:, G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973,
296:
fittings on the ends, with holes in the brass for observation. (In
337:
The original version was not reported to be used at sea, until the
216:
189:
130:
20:
1074:
Levi ben Gerson and the Cross Staff Revisited, Bernard R Goldstein
541:
440:
436:
401:
230:
201:
122:
98:
94:
83:
93:(and scientific fields that use surveying techniques, such as
308:' version had a sliding vane on the transom as an end point.
293:
260:
149:
79:
34:
772:""Important Astronomers, their Instruments and Discoveries""
419:
vessels as per 1731, with octants not permitted until 1748.
373:
to the ends of the transoms to reduce the glare of the sun.
825:
823:
821:
126:
818:
160:). It may also take its name after its resemblance to
19:
For the plant sometimes called the Jacob's staff, see
859:, MA Thesis, Texas A&M University, December, 2005
411:, invented in 1660 by the Dutchman, Joost van Breen.
244:
developed his own Jacob's staff; Dutch mathematician
164:, referred to by the name of Jacob on some medieval
747:
745:
38:
Measuring the height of a star with a Jacob's staff
484:Cross-head, cross-sight, surveyor's cross or cross
46:is used to refer to several things, also known as
658:"The Mathematics of Levi ben Gershon, the Ralbag"
1087:
868:
742:
225:of 1088, described a Jacob's staff. Shen was an
871:"Levi ben Gerson and the Cross Staff Revisited"
833:. Taipei: Caves Books Ltd. Pages 573–575.
329:Nautical cross-staff dated 1776, on display at
284:in the drawing to the right), also called the
108:
320:
1045:, Charles Griffin & Company (1926), p.21
30:Jacob's staff in the Museo Galileo, Florence
594:
592:
590:
1023:Nineteenth Century Scientific Instruments
1017:
1015:
964:
962:
940:
752:The Oxford Companion to Ships and the Sea
705:
407:Another variant of the cross-staff was a
992:, University of Minnesota Press (2000),
587:
375:
324:
259:
33:
25:
1035:
849:
369:for the sun. Mariners took to mounting
240:, the Dutch mathematician and surveyor
1088:
1012:
959:
920:
800:
798:
796:
794:
792:
612:
380:A cross-staff appears on the current
82:, later replaced by the more precise
632:
789:
669:David G. Krehbiel "Jacob's Staff",
618:Harriet Wynter and Anthony Turner,
13:
1067:
14:
1142:
1111:Historical scientific instruments
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443:, transit, or other instrument.
117:the instrument is also called a
1048:
1003:
982:
904:
862:
836:
673:, Surveyor's Historical Society
422:
347:Treatise on the Nautical Needle
255:
78:for a simple device to measure
1025:, Sotheby Publications, 1983,
930:, Portman Books, London 1989
806:A History of Marine Navigation
764:
699:
677:
662:
651:
600:Antique Scientific Instruments
280:for length. The cross-piece (
1:
1043:A Manual of Civil Engineering
947:Nicolàs de Hilster's web site
580:
531:
236:During the medieval European
602:, Blandford Press Ltd. 1980
143:
7:
1101:Angle measuring instruments
990:The Wilderness Route Finder
547:
331:Musée national de la Marine
109:In astronomy and navigation
10:
1147:
1096:14th-century introductions
1009:Rutstrum, pp. 47-55, 64-72
341:. Its use was reported by
321:Cross-staff for navigation
219:(1031–1095), in his
179:
18:
869:Goldstein, B. R. (2011).
829:Needham, Joseph. (1986).
573:As a symbol in Scouting:
1041:Rankine, William J. M.,
575:5th World Scout Jamboree
417:Dutch East India Company
415:longer allowed on board
311:
129:to determine a vessel's
968:Bruyns, Willem Mörzer,
754:, Peter Kemp ed., 1976
622:, Studio Vista, 1975,
1116:Navigational equipment
915:A Regiment for the Sea
890:10.2979/aleph.11.2.365
846:Cologne, 2010. p. 214.
720:10.2979/aleph.11.2.365
620:Scientific Instruments
385:
361:but is a cross-staff.
334:
273:
264:A Jacob's staff, from
172:simply comes from its
152:, specifically in the
39:
31:
1126:Surveying instruments
1021:Turner, Gerard L'E.,
804:May, William Edward,
382:Seal of New York City
379:
328:
263:
37:
29:
1131:Celestial navigation
1106:History of astronomy
598:Turner, Gerard L'E.
270:Practical Navigation
855:Swanick, Lois Ann.
211:theorizes that the
138:radius astronomicus
1079:2020-01-10 at the
1000:, pp. 47-55, 64-72
952:2014-03-11 at the
926:Daumas, Maurice,
684:Stern, Dr. David.
644:2007-06-12 at the
513:Surveyor's sextant
386:
339:Age of Discoveries
335:
298:marine archaeology
274:
215:Chinese scientist
40:
32:
936:978-0-7134-0727-3
686:"The Cross Staff"
559:Cross of St James
518:Surveyor's target
222:Dream Pool Essays
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774:. Archived from
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464:surveyor's cross
204:around 400 BCE.
16:Measurement tool
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646:Wayback Machine
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564:Pilgrim's staff
550:
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425:
351:Johannes Werner
323:
314:
258:
194:Jacob ben Makir
186:Levi ben Gerson
182:
154:Book of Genesis
146:
111:
24:
17:
12:
11:
5:
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1034:
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939:
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903:
884:(2): 365–383.
861:
848:
835:
817:
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763:
741:
714:(2): 365–385.
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508:Optical square
505:
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498:Holland circle
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493:Circumferentor
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474:Optical square
471:
424:
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343:João de Lisboa
322:
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257:
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242:Adriaan Metius
209:Joseph Needham
181:
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1031:0-85667-170-3
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998:0-8166-3661-3
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978:90-6011-907-X
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814:0-85429-143-1
811:
807:
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778:on 2009-01-23
777:
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760:0-586-08308-1
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250:Regiomontanus
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246:Gemma Frisius
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205:
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198:Georg Purbach
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53:
49:
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44:Jacob's staff
36:
28:
22:
1121:Song dynasty
1050:
1042:
1037:
1022:
1005:
989:
984:
969:
942:
927:
922:
914:
906:
881:
877:
864:
856:
851:
843:
838:
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805:
780:. Retrieved
776:the original
766:
751:
711:
707:
701:
689:. Retrieved
679:
670:
664:
653:
634:
619:
614:
599:
535:
527:
503:Miner's dial
479:
473:
467:
463:
459:
455:
447:
445:
435:refers to a
432:
426:
423:In surveying
413:
406:
387:
371:smoked-glass
363:
358:
346:
336:
315:
302:
289:
285:
281:
275:
269:
266:John Sellers
256:Construction
235:
220:
213:Song dynasty
206:
183:
169:
147:
137:
135:
118:
112:
104:
63:
59:
55:
51:
47:
43:
41:
842:Ralf Kern:
569:Tacheometry
523:Abney level
488:Graphometer
460:cross-sight
448:cross-staff
433:jacob staff
431:, the term
409:spiegelboog
290:transversal
278:graduations
238:Renaissance
227:antiquarian
170:cross staff
166:star charts
119:cross-staff
60:ballestilla
52:ballastella
48:cross-staff
1090:Categories
988:Rutstrum,
782:2006-10-31
671:Backsights
581:References
532:In geology
456:Cross-head
349:of 1514.
115:navigation
76:navigation
64:balestilha
56:fore-staff
898:142638690
736:142638690
554:Backstaff
446:The term
429:surveying
390:backstaff
202:Chaldeans
174:cruciform
158:Gen 32:11
144:Etymology
91:surveying
72:astronomy
42:The term
1077:Archived
1059:DOI Link
950:Archived
691:11 April
642:Archived
548:See also
400:and the
394:quadrant
367:altitude
355:John Dee
333:, Paris.
217:Shen Kuo
190:Provence
131:latitude
84:sextants
21:Ocotillo
542:outcrop
538:bedding
441:compass
437:monopod
402:sextant
345:in his
306:Frisius
286:transom
231:Jiangsu
180:History
176:shape.
125:or the
123:Polaris
99:ecology
95:geology
62:, or a
1029:
996:
976:
934:
917:, 1574
896:
812:
758:
734:
726:
626:
606:
398:octant
272:(1672)
80:angles
894:S2CID
878:Aleph
874:(PDF)
732:S2CID
724:JSTOR
708:Aleph
639:Orion
468:cross
312:Usage
294:brass
162:Orion
150:Jacob
1027:ISBN
994:ISBN
974:ISBN
932:ISBN
810:ISBN
756:ISBN
693:2018
624:ISBN
604:ISBN
97:and
74:and
58:, a
54:, a
50:, a
886:doi
716:doi
466:or
427:In
392:or
288:or
188:of
127:sun
113:In
89:in
70:in
1092::
1014:^
961:^
913:,
892:.
882:11
880:.
876:.
820:^
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458:,
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888::
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738:.
718::
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