PLOTS OF COASTAL TRIANGULATION MAP ROSLYN

PLOTS OF COASTAL TRIANGULATION MAP ROSLYN

what you see here is a raster image of a very small piece of a very large map that the DeLorme people have put into a computer program that i use a lot in my surveying job. it is showing a series of lines and points that were plotted in the program showing as best as possible the modern-day and most-probable locations of the triangulation stations, azimuth points, and bearing points that you can see on the photo of the Chesapeake Bay Progress Sketch Map, just previous to this entry. i really wish i knew more about the Coastal Survey. but this is what i do know.
what you see here is a photo of a very small piece of a very large map. i really wish i knew more about the Coastal Survey. the map is entitled as a Progress ‘sketch’, showing at the time of its publishing in 1873, how much of the entire Chesapeake Bay had been surveyed by the field mapping section of the department, The United States Coastal Survey. the sketch map is hanging on a wall of my home.
what i do know is that numerous of the best and brightest men graduating from the U S Military Academy at West Point, New York, would almost automatically gravitate to the Army Corps of Engineers and that the U S Coast Surveys borrowed from this source of talent rather liberally. a gentleman named E. O. C. Ord, who was present as a Union Army corps commanding general, appeared in the parlor of Wilmer McLean, at Appomattox Courthouse on 9 April, 1865, as Lee signed the surrender papers. from the annual reports of field activities of the Coast Survey map-makers, it can be noticed that Ord had gotten a job on one of the survey crews and one of his first assignments had been mapping the James River in the early 1850’s.
those folks who are interested in Colonial Heights history can begin to enjoy the tale that unfolds herewith: if you look carefully at the Appomattox River section of the map, you will notice a circle with lines spoking to the north, east, and south, and an annotation, "Brick House", that shows the map historian that the Coastal Survey mappers used one of the house chimneys as a reference point. also on the west banks of the Appo can be seen circles labeled "Walthall", "Hare", "Archer", and "Rosylyn", and even inside the city of Petersburg are circles "Pres. Ch.", and "Meth. Ch.".
this is where the story gets technically interesting…taking a look at the map just to the northeast of Petersburg you can see a thickly drawn line labeled "BASE", not due to any precognition of Fort Lee being nearby oneday in the distant future. a shortline railroad venture, the City Point Railroad, had been run through from Petersburg to City Point, that was apparently financed by merchants of the two communities who were a bit tired of the fact that the siltating of the river prevented many ocean going vessels from getting all the way up-river to Petersburg’s wharves. goods and tobacco hogsheads had to be loaded onto smaller barges to navigate this piece of the stream. why not link things up with the newfangled railroad cars, and bypass the good-old-boys running the river barge companies? so the map-makers were savy enough to use the clearing of this railroad from a point just across the road from the present-day Va Power center, thence up the arrow-straight right-of-way, to another point just shy of where the rails crossed Harrison’s Creek. they measured the heck out of this line, anchored on each end with a small stone monument sunk in the ground with a ‘x’ chiselled on the top, pulling right on the ground surface, marking the ‘pulls’ with small nails, dozens of times, applied in their calculations the proper temperature corrections for their brass metal chains, until they had ascertained that the God’s-Mind distance was no more than 3 hundredths of a foot of difference from the calculated-on-paper distance. this is about 3/8" for carpenters, architects and other civilians…
then the survey crew would build a wood-frame tower over each monument, usually about 75 feet tall. a hole was in the platform flooring at the top and a wood frame was constructed right over this hole. a large brass theodolite instrument was then mounted on the small frame, and a 2 pound plumb-bob was suspended via a strong piano wire from the center of the instrument down the 25 yards to the ‘x’ in the stone monument. then the crew sets an oil lamp with a shiny reflector (you’ve seen an example of one if you have ever been to a Cracker Barrel restaurant) onto the center-plumbed upper frame of the other tower, waits till twilight, climbs up to the top platform of the opposing tower, levels up the theodolite perfectly using the vial bubbles mounted on the plate of the instrument, centering the plumb-bob right over the chiseled ‘x’ down below, and begins the tedious task of turning a multitude of ‘azimuth’ angles from the north star to the center of the oil light on the tower a mile away.
i do not know the exact procedure involved in this operation, but can reasonably guess this process involved doing something akin to what i would do with a K&E transit years ago when i first began to learn the science and art of surveying at the highway department in 1973. the crew would turn the interior angle from Polaris to the other tower’s lamp, with the original setting at ‘0’ degrees. if your ‘eye-man’ is on the western tower, let us say the first angle is 80degrees, 55minutes, 10seconds. the ‘notekeeper’ then has to record in the crew notebook the angle and the exact time of the Polaris observation. when the next observation is recorded a few minutes later, the seconds could have increased or decreased by 1 or 2, due to the fact that Polaris is really appearing to rotate in a very small but significant circle around the ‘true north’ of the exact spin-spot of the Earth’s northern polar axis. all of this observed information will need to be corrected later on, rather laboriously, by using the ‘pole star ephemeris book’, which will contain all of the angular offsets between ‘true north’ and the ‘star position’ of that particular recorded time. over the course of the night the same angle is ‘turned’ dozens of different times. the starting angle which is ‘loaded’ into the instrument will also vary, using 45degrees, 90degrees, 135degrees…and so on till the entire circle of the instrument is utilized, ensuring that the miniscule differences in the machine tooled cuts made by the theodolite maker will be averaged out into a ‘differential oblivion’ that will make the angle as perfect as humanly possible, another "God’s Mind" mathematical derivative that will be used to calculate the exact position on the Earth’s surface of the chiseled ‘x’ on that monument.
once the two exact positions of the ‘x’es have been calc’d, the process kicks into a higher gear, with the survey crew placing monuments and accompanying towers at places along the river banks and bluffs that can later be seen easily from survey boats..at each tower the theodolite is setup, the twilight falls and observed angles are made between the oil lamps mounted on 2-6 other towers, as well as lamps setup on the centers of house chimneys and church belfries, again, and again, and again. then the ‘Laws of Sines and Co-Sines’ will be mathematically applied again, and again, to find the exact positions of all of the survey towers and eventually all of the physical features on the Globe’s surface.
the survey boats that were mentioned earlier will be crewed by 3-4 men… one of whom will be taking depth soundings with a metal-cup sampler tied to a knot-marked line, one of whom will be acquiring separate compass bearings to two of the still erect theodolite towers, or a tall and brightly painted ‘beanpole’ with a signal flag attached on top, suspended by tripod-bracing woodwork over any number of monuments, or a church steeple, or a house chimney near the river bank, one of whom will be recording all the observations being called to him in a field notebook, and two of whom will be rowing the boat along with long poles between observation points and holding the boat still while the others do an observation of the boat-position and the river-bottom compostion. in the time honored and tested tradition of keeping a ‘pilot’s rutter’, or ‘pilot’s rudder’, this process is accomplished by men who take the job of terrestrial and marine mapping very, very seriously, to say the very least….
when they have returned to their lodgings at night, they will probably eat a good meal of the ducks, geese, or deer (or even a few bass) they shot during the course of the day, followed by a few hours of ‘plotting onto a vellum work map’ the day’s worth of notes from the notebook. as any coastal pilot can tell you, you simply take your chart, with a series of compass roses sketched in at various places, your notes giving you either ‘true north’ or ‘magnetic’ bearings from the noted landmark points, your parallel bars ‘walking’ over from compass rose to the area being plotted, and two or three fine-pencil-lines intersecting together to re-establish the point where the observation was made. gradually a very accurate picture of the river banks, the contouring of the river bottom, and the material compostion of the bottom, will begin to emerge on the ‘vellum rough-map’. this can be rolled up in a tube and sent off to the cartographers in D.C. to be checked and plotted onto a huge copper plate which will eventually be used to intagliographically print a map of the Appomattox and James rivers, and it will be sold to pilots and captains for their navigations of the waters of the Commonwealth in a safe and timely manner.
this first ‘scientific mapping’ of the United States was one of our most fundamentally important public works projects, which later on proved extremely important in the mapping of the engagements of the Civil War, the engineering of river channeling and dredging projects, the initiation of the Space Program, the success of the Cold War, and the implementation of the GPS Systems which you now use to find the nearest Cracker Barrel restaurant…
BUT, the real value of the map in the eyes of the modern day observer is that everytime a triangulation tower is constructed, it is also NAMED for the family that owned the land under it. so you have a few names showing up that to the current area denizens are quite familiar to the ears. some of my way-back-in-time ancestors show up; the Farrar, the Cox, and the Strachan family names are on my Father’s side of the tree. and after the Civil War, when Reverend Strachan was trying to get his land back from the US government, i would think that he made some sort of argumentative point that he had allowed the Coastal survey crews to come on his property in the early 1850’s to build one their towers just to the north of Point-of-Rocks, and that perhaps he extended to the various members of the itinerant crews a goodly portion of his Old Virginia hospitality, his smokehouse treasures, and the warmth of his hearth.
HENRICUS
www.henricus.org/

DAUBER-DASH
www.sportsbackers.org/events/henricus-dauber-dash

BLUE SKY HANG-GLIDER PARK
www.blueskyhg.com/

DUTCH GAP CONSERVATION AREA
www.chesterfield.gov/Parks

HENRICO COUNTY DEPT. PARKS AND RECREATION
www.co.henrico.va.us/rec/

VIRGINIA DEPT. OF HISTORIC RESOURCES
www.dhr.virginia.gov/

KINGDOM OF LUCERNE
www.kingdomoflucerne.com/

www.flickr.com/photos/22616393@N04/5901429655/

www.flickr.com/photos/22616393@N04/6857095604/

DENNIS TAFLAMBAS
www.dktassociates.com/

Posted by OLD VIRGINIA SURVEYOR on 2011-08-19 00:46:12

Tagged: , DOWNING SURVEYS, ASHLAND, VIRGINIA , UNITED STATES COASTAL AND GEODETIC SURVEY MAPS , HENRICUS HISTORICAL PARK , DUTCH GAP , VARINA , HENRICO , CHESTERFIELD , JAMES RIVER , APPOMATTOX RIVER , old virginia surveyor @ hotmail dot com , MODERN DAY SURVEYING , COUNTRY BOUNDARY LINE SURVEYING , HANOVER COUNTY, VIRGINIA , FUN AT WORK , MAPPING , BACK COUNTRY ROADS OF AMERICA , MAPS , SURVEYING HISTORY , BOUNDARY LINES , THE COMMONWEALTH OF VIRGINIA , COUNTRY LIVING , JOYS OF LIFE , coastal maps , henricus , jamestown , contact period , THE HISTORIC POWHATAN RIVER , VIRGINIA’S RIVER LIFELINE , TIDEWATER VIRGINIA , THE RIVER OF KING JAMES I

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