SIYG.TXT Glossary of Surveying Words 61 Chapter G Glossary of Surveying Words Abney level: A hand held instrument for measuring inclination precise to about 0.2 degrees. There are several manufacturers. Cost about $75 to $150. Acre: 10 square chains. 43560 square feet. Aerial photo: A photograph taken straight down from a high altitude airplane so that the photo looks like a map. Are: Pronounced "air". 100 square meters. Azimuth: The common method of giving compass directions, whereby a full circle is divided into 360 degrees, starting at North and turning clockwise. I'm told that this doesn't apply in the Southern Hemisphere. Backsight: Instrument readings taken to the FROM station, from the TO station, but recorded as if the sight were taken normally. Blunder: A BIG mistake, obvious and correctable. Brunton pocket transit: A sighting compass precise to about 0.5 degree. Brunton makes the original; there are several imitators. Also known as Army Artillery Compass when graduated in gradians to confound The Enemy. Cost: about $200. Cardinal direction: Any one of the four directions; North, East, South, or West. Chain: 66 feet. 4 rods. Clinometer: Inclinometer. A device to measure inclination. Closure Error: When surveying in a loop and making the ending station the same as the beginning station, the calculated distance between these two stations. Compass direction: A direction from one station to another station, measured as azimuth. Corner: A point on a property boundary, established to define that boundary. Cosine: Abbr. COS. Pronounced "cosign". A mathematical function of an angle, equal to the adjacent side divided by the hypotenuse (longest side) of a right triangle containing that angle. SIYG.TXT Glossary of Surveying Words 62 Declination: The angle difference between the compass direction towards Magnetic North and that towards True North. Departure: What professional surveyors call the east distance. Elevation: The distance above (or below) an arbitrary zero level. Error: The difference between a measured value and reality. Forester's Compass: Staff Compass. A surveying compass precise to about 0.2 degrees. Cost: $400. Furlong: 10 chains. 660 feet. Gradians: A method of giving compass directions, whereby a full circle is divided into 400 gradians, starting at North and turning clockwise. The Army uses this to confuse The Enemy. Hectare: 100 ares. 10000 square meters. 2.47 acres. Inclination: The angle in degrees between a line of sight and horizontal. Up is +, down is -. Inclinometer: Clinometer. An instrument to measure inclination. Land description: The written definition of a piece of property. Latitude: What professional surveyors call the north distance. Legal description: A land description typed by an attorney's secretary. Lensatic compass: Also known as the Army Marching Compass. A diabolically engineered compass graduated in bassackwards whatchamacallits in order to totally confuse The Enemy. Precise to about 10 degrees. Cost: about $10. Line: A part of a property boundary between two corners. Link: A hundredth part of a chain, 0.66 feet. Magnetic North: The direction towards the Magnetic North Pole. This is where the compass needle points. Pace: The distance covered in one step. Usually between 2.5 and 3.0 feet. 1000 double paces of 2.64 feet define the mile as 5280 feet. Perch: A rod, a pole, 16.5 feet. Percent closure error: The closure error divided by the run times 100%. SIYG.TXT Glossary of Surveying Words 63 Plat: What professional surveyors call a map. Pole: A rod, a perch, 16.5 feet. Quadrants: An archaeic method of giving compass directions, utilized to simplify the arithmetic B.C. [Before Calculator] Presently used to keep landowners stupid. Radians: A mathematical method of measuring angles, used by some calculators, computers, and pure mathematicians. A Radian = 57.2957795131 degrees. Ranger: A sighting compass imported by Silva Compass, precise to about 1 degree. Cost: about $40. Rod: A perch, a pole, 16.5 feet. Rood: 40 square rods, perches or poles. 10890 square feet, one quarter acre. Rope: 20 feet. Run: The distance surveyed since an arbitrary starting station. Sine: Abbr. SIN. Pronounced "sign". A mathematical function of an angle, equal to the opposite side divided by the hypotenuse (longest side) in a right triangle containing that angle. Square perch: A square rod, 16.5 * 16.5 = 272.25 square feet. Staff Compass: Forester's Compass. A surveying compass precise to about 0.2 degrees. Cost: $400. Station: A place where surveyor's measurements are taken. Stringbox: A distance measuring instrument which operates by measuring a thread pulled from it. Tape distance: A distance from one station to another, usually measured in feet. Theodolite: A surveying instrument which can measure the angle between two directions, as well as the angle between a direction and Magnetic North. Precision: about 0.01 degree. Cost: $thousands. Topo map, topographic map: A map showing the shape of the surface of the land. In the United States, usually a 7.5 minute map at 2000 feet per inch showing all surface features. Cost: about $3. SIYG.TXT Glossary of Surveying Words 64 Transit: A surveying instrument, similar to a theodolite, which can measure the angle between two directions, as well as the angle between a direction and Magnetic North. Additionally, the sights can be easily turned around (transitted) to obtain a backsight. Precision: about 0.01 degree. Cost: $thousands. True North: The direction towards the North Pole. Another last chance to tell you to take precise compass readings, with a double check and a backsight. Nearly all your error is in the compass with the poor man's method of land surveying. If there are any other surveying words which you think that I should define here, then tell me them. Dave Beiter CAVE, Inc 1/2 Fast Road Ritner, KY 42639 606/376-3137