Notes and Suggestions for Botanical Garden Surveyors - Part 11
ByWalt Dunlap, Mapping Specialist, The New York Botanical Garden
As a mapping specialist at The New York Botanical Garden and a professional land surveyor for the last 20 years, I am offering consulting services on land surveying to any garden that is mapping or planning to map their collections or garden.
ACCURACY– see Part 5 of survey basics.
ANGLE – a value expressed in degrees, or parts, being a fractional or whole value of a circle which contains 360°, based on the ancient calculation of the number of days in a lunar year.
AZIMUTH – from the Arabic al-samt, a direction expressed by degrees, or parts, referenced from a specific orientation. Generally this is a 0° to 360° value based on a 0° north or south in a clockwise direction.
BACKSIGHT – the point (or line) from which observations at a TRAVERSE POINT are referenced.
BASIS OF BEARING – the specified reference of a survey, legal description or traverse. It may be observed directly, such as with a sighting of the Sun or stars or between two known marks, or calculated by INVERSE between sighted objects.
BEARING – a direction expressed by degrees, or parts, referenced from north or south and heading toward the east or west, e.g. north 50° east, north 30° west, south 12° west, south 62° east.
BENCHMARK – a point of established elevation.
BENCH RUN – a series of connected elevation observations to or from a BENCHMARK.
CLOSED TRAVERSE – a series of observed lines, defined by a common reference, with distances measured and returning to the starting point or POINT OF BEGINNING. It is used by surveyors as a series of sides of a closed geometric figure on the ground that may be used as the basis for additional observations or object sightings.
CONTROL POINT – a location of known survey value.
DATUM – the common reference elevation to which other points are related, such as mean sea level. (For geodetic surveying the datum is also specified for X and Y values.)
FORESIGHT – the forward point (or line) to which observations are made from a TRAVERSE POINT.
INVERSE – the calculated distance and orientation between two objects derived from trigonometric calculation.
OPEN TRAVERSE – a series of observed lines that do not return to the POINT OF BEGINNING.
ORIGIN – the point at which the value of both X and Y equals zero. In plane surveying this is often an unobtainable location and one used merely for the convenience of calculations.
POINT OF BEGINNING – the first-occupied TRAVERSE POINT of a survey; also the beginning point of a legal description in a deed.
PRECISION – seePart 5 of survey basics.
RANDOM TRAVERSE – a traverse whose final basis of bearing is derived from observations made during its execution. Most modern surveys are conducted in this manner. The TRAVERSE POINTS are set as with convenience of occupation and sighting as paramount.
TRAVERSE POINT – the location of an angle or bend in the traverse; also the physical object which represents it such as a nail, a monument, a pipe, a hub, etc..
TURNING POINT – the place where rod readings are taken for a continuous bench run.
X, Y, Z – the three-dimensional qualities of a point; X is the east-west value from the ORIGIN, Y is the north-south value and Z is the elevation referred to the DATUM.
N.B. to the more technically minded readers, this is intended as a simplified glossary, any suggestions or recommendations for improvement are welcome.
- TO BE CONTINUED -
Updated February 26, 2001.
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