CE 203 Terms (Spring 2025 final)

surveying

the science, art, and technology of determining the relative positions of points above, on, or beneath the earth’s surface

geomatics

the discipline concerned with the collection, distribution, storage, processing, analysis, and presentation of geographic data or geographic information

2 ppm

the difference between the US survey foot and the international foot

Geoid

approximates the height/relief of earth

Ellipsoid

approximates the shape of earth

map projection

the regular surface of earth projected onto a map sheet

vertical datum

a geoid used to approximate the mean sea level; geometrically irregular

undulation (N)

geoid height

orthometric height (H)

height above or below the geoid height

ellipsoid height (h)

the height from the ellipsoid given by GPS

horizontal datum

reference for the horizontal location of Earth (latitude/longitude)

precision

consistency of repeated observations, or internal consistency

accuracy

difference between recorded values and true values

projected coordinates

(x,y) coordinates (Northing/Easting) converted from latitude and longitude

mercator projection

a cylindrical mapping projection that is useful for mapping the equator (scale is only true at the Equator but increasing distorts as the map approaches the poles)

transverse mercator

a mercator mapping projection rotated 90 degrees (true at Greenwich meridian)

universal transverse mercator

a map projection where the world is split into 60 zones (6 degrees each), with each zone having a transverse mercator applied to it

vector data model

a data model that represents reality as points, lines, and polygons (irregular shape, irregular size)

raster data model

a data model that represents reality as cells of numeric values (pixels) (regular shape, regular size)

TIN (triangulated irregular network)

a data model that takes sample points and connects the sample points with lines (irregular size, regular shape)

main file

a component of a shapefile that is a variable record-length file, in which each record describes a shape with a list of its vertices; user has direct access

index file

a component of a shapefile that contains records with the offset (computer address) of the corresponding record in the main file

dBASE file

a file that contains the feature attributes with one record per feature