CLASSIFICATION OF SURVEYS, MAPS AND PLANS, MAP CHARACTERISTICS Flashcards
Name the methods in which classification of surveys can be done
- Based on instruments
- Based on methods
- Based on purpose
- Based on nature of field
Classification based on instruments
- Chain Survey (Chain & offset survey)
only linear measurements are made with a chain/tape - Compass survey (chain & compass survey)
linear measurement with chain, angular measurements with magnetic compass - Plane table surveying
graphical method that involves field and plotting simultaneously - Theodolite survey
horizontal angles measured by theodolite and linear measurements made with chain/tape - Tacheometry survey
special theodolite used to determine horizontal and vertical distances indirectly - Levelling survey
determines vertical distances/elevations and relative heights of points using a level - Photogrammetric survey
measurements taken using photographs from aerial camera/Aircraft - EDM survey
all measurements made using EDM instrument i.e total station
Classification based on methods
- Triangulation
area divided into network of well conditioned triangles - Traversing
traverse - circuit of survey lines open/closed
linear, horizontal angles measured
Classification based on purpose
- Geological survey
surface/subsurface surveying for location of minerals, rocks, folds, faults - Mine survey
surface and underground surveys for exploration of mineral deposits and tunnel guidance - Archaeological survey
locate relics of antiquity, civilization, kingdoms…. - Military survey
locate strategic positions for army operations
Classification based on nature of field
- Land survey
preparation of plans and maps of given areas eg. topo maps, cadastral surveys/// - Hydrological survey
conducted on/near water bodies
includes locating shorelines of water bodies - Astronomical survey
determine latitudes, longitudes, azimuths, local time using heavenly bodies - Aerial/photographic survey
photographs of the earth’s surface taken in overlapping strips of land - Hydrographic survey
Science of measurement and description of features that affect maritime navigation, marine construction, dredging, offshore wind farm, offshore oil exploration and drilling
What is a plan?
A plan is the graphical representation to some
scale, of the features on, near or below the surface of the earth as projected on a horizontal plane. i.e., uses a large scale
What is a map?
a small-scale graphical projection on a horizontal plane, i.e. a small scale plan (shows more)
What is map scale?
Map or cartographic scale is the ratio of a
distance on Earth compared to the same
distance on a map.
What are the 3 types of map scales?
- Written/verbal scale
- Graphic scale
- Fractional scale
What is map generalization?
This is whereby a small scale is used on a map, thereby not showing a lot of detail of various features represented as there is not enough room.
What does scale selection/choice depend on?
- Purpose
- Size
- Required precision of plotting
What are map projections?
Map projections are a mathematical model
for converting locations on the earth’s
surface from spherical to planar
coordinates, allowing flat maps to depict
three-dimensional features.
They distort shape, area, distance or direction to some extent.
Possible functions of map projections
- preserve integrity of shape
- preserve accuracy of area, distance or direction
What does map quality constitute?
- Accuracy
- Completeness
- Consistency
- Timeliness
What factors determine map accuracy?
- Accuracy of original data used to compile the map
- The accuracy of data transfer onto the map
- Printing or display resolution of the map
