We are developing a field data collection system as a part of my patented land surveying process. 　We are about to launch a pilot project in SW Florida and if you would care to participate as part of the processes we are developing please notify me John Veatch PLS @　[email protected]

John Veatch

Someone asked "what is It? to Jill's posting of the sextant.

A sextant was developed for mariners to determine latitude at sea.

The history of mariners instruments in chronological order is: Astrolabe; backstaff, quadrant, octant and sextant. Today all of them are considered antiques, although some small boat mariners like to use a sextant for the pleasure of it.

Quadrant, octant, and sextant do indicate the portion of a circle they measure  90 degrees, 45 degrees and 60 degrees ...octants and sextants, with the help of their reflecting mirrors could measure angles up to 90 degrees and 120 degrees respectively(remember the physics principle that the angle of reflection equals the angle of incidence).

Sextants by themselves could ONLY measure latitude. and even then on  a pitching ship the mariners ability to coincide the celestial body with the horizon was so difficult it was hard to get an accurate measurement.  When chronometers came along, the ability to get an accurate measure of time at the time the sextant measurement was taken created the ability to fix both latitude and longitude....REMEMBER...it was navigators who first created the demand for position fixing!!

Sextants on land had another problem...determining true horizon was difficult UNLESS YOU WERE on a dead flat piece of property at sea level....even if the land was flat but was 5000 feet above sea level (yes, there are places like that in Wyoming) the elevation created an  inaccurate reading.  SOOO, position fixing on land soon was done with artificial horizons, astronomical transits, chronometers  and variations of these instruments.

Check out some of the  antique surveying instruments in my albums.

David C. Garcelom

Thanks, many of them come from the Virtual Museum of Land Surveying, I recommend it for old surveying photos.