Home > Flashcards > Print Preview
The flashcards below were created by user
ichiban2008
on FreezingBlue Flashcards. What would you like to do?

Cartography
the art, science, and technology of making various maps.

Ellipsoid
a closed quadric surface that is a three dimensional analogue of an ellipse
Spheroid
 approximates the shape of a sphere
 created by rotating an ellipse about either its major axis (called a prolate spheroid) or its minor axis (called an oblate spheroid)

Rhumb Line
Any straight line on map  line of constant direction
not the shortest distance between two points

Cadastral map
provides the location of propertyownership lines with their bearings,length, ownership, and size
SLOB

Great Circle
any circle drawn on Earth’s surface whose center coincides with the center of Earth
Examples:
 Good for navigation
 Gives you the shortest distance
The shortest distance between two points on Earth surface

Small Circle
circles whose centers do not coincide with the center of Earth
Examples:
All parallels except the Equator

Principle Meridian
 an imaginary line on the Earth's surface from the North Pole to the South Pole that connects all locations with a given longitude
 Each is half of a great circle on the Earth's surface
 the principal northsouth line used for survey control in a large region

Map Projection vs Coordinate System
Map projections and coordinate systems are distinct concepts that serve two different purposes in georeferencing; Georeferencing Meaning finding locations
The function of map projections is to define how positions on the earth’s curved surface are transformed onto a flat surface
A coordinate system is then superimposed on the surface to provide the referencing framework by which positions are measured and computed

NAD 27 vs NAD 83 vs WGS 84
Taken together, the Clarke 1866 reference ellipsoid and the geoid origin of Meades Ranch comprimise the North American Datum of 1927 (NAD27)
However, since the advent of satellite geodesy, large errors have been encountered when comparing the results of today's highly accurate survey techniques with the NAD27 values
To remedy this, a new reference ellipsoid, the Geodetic Reference System (GRS), was recommended by the International Geodesy and subsequently adopted by the National Geodetic Survey, creating the North American Dantum of 1983 (NAD83)
When to use:
 NAD27: if you are in N. America, and want to match your NAD27 topo maps.
 NAD83: if you are in N. America, and are collecting raw data.
 WGS84: if you are going to compare with GPS data you have collected elsewhere in the world.

Datum and Datum shift
Datum
A datum is the mathematical model that fits the earth to an ellipsoid. It is a reference from realworld to this ellipse
 The earth’s surface is not perfectly round. Instead, it is ellipsoid, with mountains and valleys
 Datum are used to correct for these undulations (wavy surfaces).
 A datum is a geodetic reference system that specifies the size and shape of the earth
 Base point from which the latitude and longitude of all other points on the earth’s surface are referenced
Datums and the coordinate systems based on them were developed to describe geographic positions for surveying, mapping, and navigation
Over the years, datums evolved from spherical to ellipsoidal models using satellite measurements. The earth is not a sphere, but an ellipsoid flattened slightly at the poles and bulging somewhat at the equator
The ellipsoid is used as a surface of reference for the mathematical model of the earth. Since mathematical models of the size and shape of the earth are now more precise, it has become necessary to change to a more accurate model
Datum Shift
 Datum shifts are differences in the mathematical formulas between datum
 Datum shifts must be taken into account when reprojecting data, or comparing data of different datum, or else error will be introduced

Tissot Indicatricts
a geographical device plotted on a map projection that illistrutates the kind and extent of distortion at infinitesimally small points
(best def) provides a visual means of showing how distortion varies at point locations across a projection (best def)
provides a quantitative analysis of distortion that describes the amount and type of distortion that occurs at points across a map

Use Illinois east zone as example to explain how SPCS is defined
State Plane Cordinate System
Uses the Lambert Conformal Conic Projection for states like Tennessee and Oklahoma
Uses Transverse Mercator Projection for states like Illinois
set of 124 geographic zones or coordinate systems designed for specific regions of the United States
Each state contains one or more state plane zones, the boundaries of which usually follow county lines

Use Illinois zone 15 as an example to explain how UTM is defined
 60 UTM Zones
 each zone covers 6° longitude
 False origin, false easting, false northing, Central meridian (500000 m, 0 m) (fancy way of saying x.y)
 State of Illinois: zone 15 and zone 16
 Use zone 15 as an example to explain how UTM is defined: false origin (0 m, 0m) on the Equator, central meridian (93º w)

List any 2 functions that maps provide
Map are especially effective devices for recording and communicating information about the environment
Maps clearly preserve the locational attributes of that information (i.e., show the relationships between one feature and another)
Maps can also indicate distances and directions between locations, or the areas occupied by different types of land uses or features
Maps are useful for determining the patterns formed by many types of distributions on the earth surface (e.g., roads, villages, cities, streams, lakes, …)

Definition of map
neatly drawn, bird's eyed view of the earth’s surface
graphic representations of the environment, both cultural and physical

Equivalent vs Conformal
Equivalent
preserves area
When a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the Earth that they represent, the map is an equalarea, or equivalent, map.
Conformal
preserves shape
When the scale of a map at any point on the map is the same in any direction, the projection is conformal. Meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles.

Concept of Projection
a systematic transformation of the Earth's graticule and landmass from the curved two dimensional surface to a flat two dimensional planimetric surface
The line of tangency between a projection surface (cylinder or cone) and the surface of the reference is called the standard line of the projection. If it is along a parallel, as is often the case, it is called the Standard Parallel
There is no distortion along the standard line(s) because there is a onetoone relationship between the projection surface and the globe. Away from the standard line, however, distortion occur
Central meridian is the longitude that is designated as the center of the map projection

Developable surfaces
a surface that can be flattened to form a plane without compressing or tearing any part of it
three commonly used developable surfaces for map projections are:

Standard parallels
latitude
imaginary line that crosses the earth's surface in an east to sest fashion
measured in degrees, minutes, seconds north or south of the equator

Four spatial properties subject to distortion:
SHAPE
 When the scale of a map at any point on the map is the same in any direction, the projection is conformal.
 Meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles
AREA
When a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the Earth that they represent, the map is an equalarea, or equivalent, map
DISTANCE
A map is equidistant when it portrays distances from the center of the projection to any other place on the map
DIRECTION
A map preserves direction when azimuths (angles from a point on a line to another point) are portrayed correctly in all directions.

