lecture 2 Flashcards
what is geographic information
data with real world location
the where and what
key attributes to maps
what are some things to keep in mind ab maps
one point in time
fixed perspective
macro n micro
fine to coarse
what is analogue to digital conversion
real world characteristics turns to alpha character or string of numbers so comp can understand better
hard copy maps characteristics
one point in time, need to reprint to update info
scale and perspective fixed
tends to be scaled down, using analogues to represent things (blobs, lines, squares)
digital copy map characteristics
projection not fixed, can change perspectives
roads represented as coordinates w additional infornation w
can be readily updated
3 things required to convert irl info into comp
coordinates, projection, datum
what is a coordinate
segmented earth into scalar unities to define location
2 kinds of coordinate systems in nz
nztm2000 (made in 2000 info given in local datum. easy to measure)
wgs584 (world geographic information) uses latitude and longitude
why the coordinate systemnused in nz not good for other larger countries
cuz its too large. nz can be more specific
what is a projection
3D globe represented in a 2D map
what kinds of distortions
distance from one feature
direction from one feature
scale from one feature
shape of a feature
what are datums
the mathematical way of representing x y and z on a globoid location
whats a geoid
the potato earth
how is a geoid calculated
using gravity
whats a spheroid
the theoretical perfect circle where centre of earth is (0,0,0)
whats geocoding
determining geographic coordinates for place names, street address and codes
what is geo referencing
taking aerial image and relating it to real world coordinates
what is data model
conceptual understanding of how information is categorised and organised (why)
whats a data structure
how data is translated from real world into digital world
two ways of thinking ab world (data model)
as an object
as a field
whats vector good for
objects thibgs
can be stacked w attribute table
raster good for
feild (grid w same geographical feature)
two ways u can measure gis
categorical and numerical
whys numerical good in gis
comforms to digital archetecture, easier for computers to digest, can preform maths on data
what are the 4 categories of numerical data
nominal, ordinal, interval, ratio
nominal measuremnet
similar to id
does not have intrinsic or relative value compared to other
what is ordinal measurement
order is importwnt but does not suggest anything further
we do not know the imbetween
what is interval measurement
gap feom one to another matters but does not start from 0
therefore you cannot divide but can subtract
why is radio measurement
were distance from one another matters as well as it starts feom 0
therefore you are able to divide and subtract from data
