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Map: A graphic representation of a portion of the Earth’s surface drawn to scale, as seen from above.
Legend: Identifies the symbols used to depict the prominent natural and man-made objects that exist on the ground.
Scale: Gives the ratio of the distance on the map to the distance on the ground. The larger the ratio, the less detail can be placed on the map.
Contour Line: A line that joins points of equal elevation above a given level.
Contour Interval: Specifies the vertical distance between contour lines.
Declination Diagram: Depicts true north, magnetic north, and grid north.
True North: A line from any point on the Earth’s surface to the North Pole.
Magnetic North: The direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument.
Grid North: The north that is established using the vertical grid lines on a map.
G-M Angle: The angular distance between grid north and magnetic north.
Topographic Symbols: Used to visualize man-made and natural features.
Map colors can be used as indicators.
Major Terrain Features: hills, saddles, valleys, ridges , and depressions.
Hill: An area of high ground.
Saddle: A dip or a low point between two areas of higher ground.
Valley: A groove in the land, usually formed by a stream or a river.
Ridge: A sloping line of high ground.
Depression: A sinkhole, pit, or low point in the ground.
Minor Terrain Features: draws, spurs, and cliffs.
Draw: A small valley.
Spur: A short ridge.
Cliff: A vertical or near-vertical feature.
Supplementary Terrain Features: cuts and fills.
Cut: A man-made feature that cuts through raised ground.
Fill: a man-made feature that fills a low area.
MGRS Coordinates
The world is divided into 60 grids, and each grid is given a short letter-and-number designator.
The grid zone designator and the 100,000-meter square indentification are required to convey information about your location.
Truncated position formats can be used for less precise positions.
Phonetic Alphabet: Used to spell out letters in place of saying the letter itself.
Geographic Coordinate System
Latitude (x-coordinate): Specifies north-south position.
Longitude (y-coordinate): Specifies east-west position.
Land Measurement
Acre: Equivalent to 43,560 square feet.
Hectare: Equivalent to 10,000 square meters.
Geographic Information System (GIS): A computer-based system that can be used to precisely map a property.
LiDAR (Laser imaging, Detection, and Ranging): A land measuring tool used by surveyors.
Global Positioning System (GPS): Used for precise positioning.
Types of Surveying
Surveying / Geomatics: All methods for measuring and collecting information about the physical earth and our environment, and processing that information. Surveying is the process of determining the relative positions of points above, on, or beneath the Earth’s surface.
Geodetic Survey: The curved surface of the Earth is considered by performing the computations on an ellipsoid.
Plane Survey: The reference base for fieldwork and computations is assumed to be a flat horizontal surface.
Control Surveys: A network of horizontal and vertical monuments that serve as a reference framework for initiating other surveys.
Topographic Surveys: Determine the locations of natural and artificial features and elevations used in mapmaking.
Land, Boundary, and Cadastral Surveys: Establish property lines and property corner markers.
Hydrographic Surveys: Defined shorelines and depths of lakes, streams, oceans, reservoirs, and other bodies of water.
Alignment Surveys: Made to plan, design, and construct highways, railroads, pipelines, and other linear projects.
Construction Surveys: Provide line, grade, control elevations, horizontal positions, dimensions, and configurations for construction operations.
As-built Surveys: Document the precise final locations and layouts of engineering works and record any design changes that may have been incorporated into the construction.
Mine Surveys: Performed above and below ground to guide tunneling and other operations associated with mining.
Solar Surveys: Map property boundaries, solar easements, and obstructions according to sun angles.
Optical Tooling: Making extremely accurate measurements for manufacturing processes where small tolerances are required.
Except for control surveys, most other types of surveying use plane-surveying procedures.
Ground Survey: Utilize measurements made with ground-based equipment.
Aerial Survey: Use photogrammetry or remote sensing.
Photogrammetry: Uses cameras that are usually carried in airplanes to obtain images.
Remote Sensing: Employs cameras and other types of sensors that can be transported in either aircraft or satellites.
Satellite Surveys: Used for mapping and monitoring large regions of the Earth.
Survey Controllers: Can be interfaced with modern surveying instruments. Survey controllers can automatically receive and store data in computer-compatible files as observations are taken. Many survey controllers use the Windows operating system.
Surveying Basics
Land Information Systems (LISs) and Geographic Information Systems (GISs) are computer-based systems that enable storing, integrating, manipulating, analyzing, and displaying virtually any type of spatially related information about our environment.
LIS/GIS Themes/Layers: Political boundaries, individual property ownership, population distribution, locations of natural resources, transportation networks, utilities, zoning, hydrography, soil types, land use, vegetation types, wetlands, e.t.c.
All information entered into LIS and GIS databases must be spatially related, meaning they must be located in a common geographic reference framework.
Major U.S. Surveying Agencies: National Geodetic Survey (NGS), the U.S. Geological Survey (USGS), and the Bureau of Land Management (BLM).
Surveying Units
Plane Surveying is based on horizontal angles, horizontal distances, vertical/zenith angles, vertical distances, and slope distances.
Surveying Units: Length, area, volume, and angle.
Special rounding rules apply when surveying.
Measurement Errors
Good observations require a combination of human skill and the correct use of equipment.
Measurements are never exact and will always contain errors.
Direct Observation: Applying a measuring instrument directly to the quantity to be observed: applying a tape to a line, fitting a protractor to an angle, or turning an angle with a total station instrument.
Indirect Observation: When it is not possible to apply a measuring instrument directly to the quantity to be observed. Observations are determined by some other observed value or values.
Error Propagation: The manner in which errors in measurements combine to produce erroneous computed answers.
Error: The difference between an observed value for a quantity and its true value.
No observation is exact, every observation contains errors, the true value of an observation is never known, the exact error present is always unknown.
Accuracy of observations depends on the scale’s division size, the reliability of the equipment used, and human limitations in estimating distances closer than about one-tenth of a scale division.
Mistakes: Blunders caused by misunderstanding the problem, carelessness, fatigue, missed communication, or poor judgment.
Errors in observations stem from three sources: natural, instrumental, and personal errors.
Natural Errors: Caused by variations in wind, temperature, humidity, atmospheric pressure, atmospheric refraction, gravity, and magnetic declination.
Instrumental Errors: Result from an imperfection in the construction or adjustment of instruments and from the movement of individual parts.
Personal Errors: Arise principally from limitations of the human senses of sight and touch.
Systematic Errors (Biases): Result from factors that comprise the “measuring system” and include the environment, instrument, and observer. If conditions change, the magnitudes of systematic errors also change. A correction can be computed and applied to observed values if the conditions producing the systematic error(s) are known to exist.
Random Errors: Errors that remain in measured values after mistakes and systematic errors have been eliminated. Random errors are caused by factors beyond the observer's control. There is no absolute way to compute or eliminate random errors, but they can be estimated using adjustment procedures known as least squares.
Discrepancy: The difference between two observed values of the same quantity. A small discrepancy indicates there are probably no mistakes and random errors are small.
Precision: The degree of refinement or consistency of a group of observations and is evaluated based on discrepancy size. If multiple observations of the same quantity yield small discrepancies, this indicates high precision.
Accuracy: The absolute nearness of observed quantities to their true values.
Practice
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