Definition="and" boolean operator. creates a new vecter layer by overlaying two sets of data

input layer=polygons/lines polygons/ponts lines/lines (cannot be line/poin or point/point)

output layer lowest dimension

definition= "OR" boolean operator. creates new vector layer by placing two polygon layers on top of each other.

input=both layers must be polygon

output layer=always polygon

azimuthal-geometrically projected onto a plane. the point of the projection is at inifinity

used for prospective views of the whole planet

areas, shapes and directions only true at center point

projected onto a cone tangent at two standard parrallels

used to show aregion that is primarily east to west.

Universal transverse mercator

projected on to a cylinder with a 6° width 

good for area with mostly a north to south extent

projected on a cylinder tangent to the chosen meridian

distances only true along the central meridian

distortions increase with distance from central meridian

a document or table that describes info about the data set

-resolution

-copyright

-price

-availability

-time of acquisition

-spatial extent

-spatial accuracy

Position dilution of precision

causes

-angles of the satelites (satelites require a 60º spread between them)

-obscured satelites(deep canyons, cliffs, tall buildings)

-recalibration of satelites

-multibeam (issues due to ionosphere disruptions)

uncorrected(single antennae, hand held GPS)

differential 

real time kinematic

distance are only true along the equator

large area are distorted

distortion increses with distance from equator

perimiter and ares of polygons as well as adjacency of polygons

used for spatial analysis by linking with attributes and locations

handeled differently in raster and vector

√area/number of points

2

not a perfect correlation for measuring randomness

used for calculating distribution patterns

gradual boundaries

features on a continuous surface

combining lots of data layers

sopphisticated spatial modelling

remotely sensed data

XOR

where either of two polygons exist but not both

abrubt boundaries

spatial relationships in a network (ie roads)

lots of attribute for each area

large spatial data queries

high quality detailed maps

based on the average distance between adjacent points

where either question occurs

AND

yes or no answers

data has only two possible values

cylindrical

conic

azimuthal (planar)

use DEM (digital elevation model)

rise=the max difference between the cells z value and the z values if the 8 closest neighboring cells

run=the size of the cell

geodetic-aligns spheroid to fit particular area

Geocentric-uses earths ceter of mass as the origin

not uniform units of distance

cant get accurate distances areas or directions between points

derived from datum

defined for locations with a 3-D sphere

referenced in lattitude and longitude

-raster is always 2-D

-points have zero dimensions so they cant realistically be portrayed in raster

-lines are 1 dimensional so they cant be accurately shown either

-small features can be lost or be hard to depict

-not usefulf for measuring perimiter

-resolution

mathmatical model that describes the shape of the earth

different datums for different parts of the earth

geographic coordinate systems, locating data on a spherical surface(lats and longs)

projected coordinate systems, locating data on on to a flat surface (measured in meters)

Vector

-shapefile

-coverage

-feature class

tables

-dbase or excel

Raster

-grid

Mapfile

-no spatial data only used to dsiplay info

only include features that the map maker decided to include

typically only shows one point in time

might only cover a limited area

what is a map?

a picture of all or part of the earth 

shows where things are locted in relation to eachother

only shows part of what exists on earth at any one time

a model of reality

sends out a signal and times the response then uses this to create an image 

types 

Lidar

Radar

Sonar

only detection

uses ambient energy to create an image.

electromagnetic radiation is the most common form of energy used for this method

uses eye safe lazer of light to creat an image in a terestrial environment

-precision of 10-25 cm

basic components include

-Lazer scanning and cooling system

-GPS

-inertial navigation system

key features

creates massive data sets

rapid precise scanning

high speed autonmous post processing

-cancel out reduntant information 

-create a new data layer that highlights certain features

-exagerate differences in a new layer

TOPOLOGY STORED =Perimeter and area of polygons. Adjacency of polygons

for every polygon in GIS there will be information stored about which lines make it up and which polygons are next to each other (called contiguity)

affected by depth shorter wave lengths (blue) penetrat deeper than longer wave lengths (Red)

Turbidity- turbid water will scatter incident light and result in false bottom images

bottom reflectance

color of substrate