Text 2 Flashcards
reproject
changing a dataset from one map projection(or measurment system) to another
spatial reference
the use of real world coordinate system for identifying locations
georeferencing
a process of alligning an unreferenced dataset with one that has spatial reference information
when data is _______, each location in that data is aligned with real-world coordinates
georeferenced
control points
point locations where the coordinates are known, used to align the unreferenced image to the source
If you cant use control points the only other way to georeference is by _______
field work
the minimum number of control points required to fit the unreferences image to the source is ____
three
when referenced data is transformed, its warped to make it match up with the source:
. can be _____,_______,_______, and/or _______
rotated
skewed-distorted or slanted
scaled
translated-shifting
affine transformation
turns _______ data into _______ _____ data
a linear mathematical process by which data can be altered to align with another data source
.calculates real world X and Y coordinates for each unreferences x and y coordinate
.is a first order transformation which is the type of transformation that is usually used for this
.unreferenced data will be turned into spatially referenced data
Root mean square error
an indicator of how well the now referenced data matches with the source
resampling
when you’re georeferencing an image, new locations for the image’s pixels will need to be calculated, and in some cases new values for the pixels will need to be generated as well
geographic information system
a computer based set of hardware and software used to capture, analyze, manipulate, and visualize geospatial information
.whenever examination, maipulation, or analysis of geospatial data is involved GIS is essential
.can link non-spatial data and link it directly to a location
GIS IS a computer based set of hardware and software used to ______, ______, ______, and ______ geospatial information
capture
analyze
manipulate
visulaize
geospatial information
something that has direct ties to a location on earths surface
GIS originated in 19__s through CGIS which was designed to provide large scale mapping of land use in canada
60
FATHER OF GIS
Roger Tomlinson
GIS: two ways of viewing the world
discrete-object view:
.a conceptualization of the world in which all relaity can be represented by a series of seperate objects
-each object has a fixed location, starting and stopping point, or boundary
. modelled in GIS as series of objects
.objects represented by points, lines, and polygons
continuous field view:
.not everything has a fixed boundary or is an object
.a conceptualization of the world in which all items vary across the earths surface as constant fields, and values are available at all location along the field
.vector data model are often not best way of prespessenting data so Raster data model used instead
Three vector objects:
explain each
ARE ZERO DIMENSIONAL OBJECTS,A SIMPLE SET OF COORDINATE LOCATIONS
are one-dimensional objects, created from connecting starting anf ending points(and any points in between that give the lines its shape)
are two dimensional objects that form an area from a set of lines(or having an area defined by a line forming a boundary
vector data model
a conceptualization of the world that representes spatial data as a series of vector objects
points,lines, polygons
Digitizing
the creation of vector objects through sketching or tracing representations from a map or image source
topology
how vector objects relate to each other (in terms of adjacency, connectivity, and containment) independently of the objects coordinates
adjacency-how one polygon relates to another polygon in that they share a common boundary
connectivity- how lines can intersect with one another
containment- how locations are situated within a polygon boundary
Raster data model
a way of representing spatial data that utilizes a series of equally spaced and sized grid cells, with each square cell representing the same area on earths surface
-each grid containing a single value representing data being modelled
Columns = _ axis
Rows= _ axis
x
y
attribute
the non-spatial data that can be associated with a spatial location
.can take 1 of 4 forms
- nominal
- ordinal
- interval
- ratio
Nominal Data
a type of data that is a unique identifier of some kind-if numerical, the differences between numbers are not significant
.ex: social security number/telephone number/names or descriptive data associated with a location