note: others information about groma.
b) . Source from Wikipedia - The Groma or gruma (altered from Greek gnmon γνόμων "indicator", possibly through Etruscan) was the principal Roman surveying instrument. It was composed of a vertical staff with horizontal cross pieces mounted on a bracket. Each cross piece had a plumb line and plumb bob hanging vertically. Its main use was to survey straight lines, squares, and rectangles.
c) . Britannica - use in ancient Egypt
There is some evidence that, in addition to a marked cord, wooden rods were used by the Egyptians for distance measurement.
2. Oldest Latin manuscript - Codex Acerianus, contaion an account of surveying as practised by the Romans and includes several pages from Frontinus work.
This manuscript found in the tenth century by Gerbert.
3. Middles Ages - Arabs in Islam world was making more progress in art of surveying - "practical geometry".
4. In 13th Century - Von Piso wrote Practica Geometria which contained instruction of surveying.
He also authored Liber Quadratorum - dealing with the quadran, a square brass frame having 90degree angle and other graduated scales
5. Instruments - Astrolabe.- a metal circle with apointer hinged at its center and held by a ring at the top, and the cross staff, a wooden rod about 4-ft long with an adjustable cross-arm ar right angles to it (Wolf & Ghilani, 2002). This instruments widely used in Islamic empire.
source of image: http://www.agmgifts.co.uk/resources/astrolabe_5.jpg
1. Wolf, P.R. & Ghilani, C.D. (2002) Elementary Surveying An Introduction to Geomatic. Prentice Hall, Upper Saddle River, New Jersey
2. Wikipedia : An astrolabe is a historical astronomical instruments used by classical astronomer, navigator and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets and stars determining local time given local latitude and vice-versa; surveying; and triangulation.
In the medieval Islamic world, they were used primarily for astronomical studies, as well as in other areas as diverse as astrology, navigationm, surveying, timekeeping, Salah prayer and Qibla. Astrologers of the European nations used astrolabes to construct horoscopes.
There is often confusion between the astrolabe and the mariner's astrolabe. While the astrolabe could be useful for determining latitude on land, it was an awkward instrument for use on the heaving deck of a ship or in wind. The mariner's astrolabe was developed to address these issues.