[PPT1] Introduction to Surveying and Mapping Flashcards
Geomatics
- the science concerned with the measurement, representation, analysis, management, retrieval and display of spatial information describing both the Earth’s physical features and the built environment.
- includes disciplines such as: Surveying, Geodesy, Remote Sensing & Photogrammetry, Cartography, Geographic Information Systems, Global Positioning Systems
Surveying
- The art of making measurements of the relative positions of natural and man-made features on the earth’s surface, and the presentation of this information either graphically or
numerically. (NJDOT Survey Manual, p.3) - The art and science of determining angular and linear
measurements to establish the form, extent, and relative position of points, lines, and areas on or near the surface of the earth or on other extraterrestrial bodies through applied mathematics and the use of specialized equipment and techniques. (J.P. La Putt, 1987)
Professional Surveying
The application of knowledge of the:
– science of surveying measurement;
– legal principles of boundary location;
– laws related to boundaries & land use;
– applicable mathematical & computational theories and
principles;
– natural & other forces which affect positional accuracy;
– land planning & development concepts pertinent to
subdivision of land & property surveys;
– land record & land tenure concepts;
– geodetic & other earth-related sciences to the analysis, design, & execution of surveying & mapping projects & the design of land mapping
The Surveyor
A surveyor is a professional person with the academic qualifications and technical expertise to:
– practice the science of measurement;
– assemble and assess geographic related information;
– use that information for the purpose of planning and
implementing the efficient administration of the land, the sea and structures thereon; and
– instigate the advancement and development of such
practices.
Eratosthenes (276 BC-194 BC)
- Some claimed that his measurements are with an error
of less than 2% and that was 2200 years ago! - However, most literatures cited his measurement as
16% too big compared to the accepted modern circumference of the earth around the poles.
School of Surveying (150 BC)
School of surveying was established by Romans to teach:
* town planning
* map making and
* building of roads and aqueducts
Ptolemy produced maps (120 BC)
“If the earth was spherical then a proper representation could be obtained by a geometrical projection of that surface”
“What can be mapped could be ruled.”
An old belief that was the main reason for people to study Surveying.
Ancient Surveying Instruments
- Astrolabe
- Dioptra
- Roman Groma
- Libella
- Merchet
1. Astrolabe
- Developed sometime in 140 B.C.
- Credited to Hipparchus
- Further improved by Ptolemy
- Metal circle, pointer hinged at the center, held by a ring at the top
- Originally designed for determining the altitude of stars
- Ptolemy’s version is an astronomical instrument
on which the celestial sphere is projected stereographically
2. Dioptra
- Perfected by Heron of Alexandria
- Used in leveling and measuring horizontal and vertical angles
- Mounted on a tripod (50 cm tall)
- Apparatus pivoted on a circular plate, moved around by a worm screw, driven by a small handle
- The top plate was mounted on a toothed semicircular plate and was adjusted in the vertical plane by another worm drive.
- Angles could be read off the top disc, which was scored with two lines crossing at right angles.
- The sighting and reading elements were made of bronze.
3. Roman Groma
- principal tool used by the Roman surveyors to trace on the ground simple and orthogonal alignments, necessary to the construction of roads, city, temples and agricultural lands subdivision.
Parts of Roman Groma
- Ferramento - a pole in hollow metal equipped in the inferior extremity with metallic cone-shape point for the fixing
- Stelleta - Cross arms fixed at right angles and pivoted eccentrically upon the ferramento
- Cornicula - extremities of the stelleta where plumblines are suspended
- Rostrum - a strong pole with the cylindrical extremities: one to receive the swivel pivot of the stelletta, the other for the grafting in the vertical pole; the distance among the two cylinders is exactly a foot (0.3048 m)
4. Libella
- Assyrians and Egyptians as first users
- A-frame with a plumb line suspended from its apex and used to determine the horizontal
- Horizontal foundations of the great pyramids of Egypt defined by libella
5. Merchet
- Device for measuring time and meridian
- First used by the Chaldeans (approx. 4000 B.C.)
- By sighting through the slot and past the plumb bob string, a straight line could be projected.
