Lecture 2 Flashcards
Earths orbital revolution
an _____ path around the sun
____(angle) with the _____ plane
- An elliptical path around Sun
- Earth–Sun distance varies between aphelion &
perihelion points - 23.50 with the ecliptic plane
Celestial Coordinate system
North & South celestial pole - point in sky directly
above north/south pole on earth (zenith of north/south
pole & + 90o/- 90o respectively)
• Celestial equator – circle surrounding equator on
earth
• Ecliptic – pathfollowed by the sun through the sky over the course of the year.
declination
Declination – angle from celestial equator (0o
), positive going
UP, negative going Down
celestial Prime meridian
• Celestial Prime meridian – point where sun is located at the vernal equinox (spring)
Right ascension
Right ascension (RA)
– angle (degree) from celestial “prime meridian”
(equivalent of celestial longitude) 68
RA – typically expressed as a time going east – 0 to
24 hours is 3600
georeferencing
“To establish a relationship between page
coordinates on a planar map and known realworld
coordinates”.
Or other way
…..is the act of assigning geographic locations
to features of the spatial data that do not have
any real world coordinates
Geographic transformation
Transformation involves: _____, _____, ______, and ______ a dataset to a given set of
geographic or projected coordinates
“The process of converting a digitized map, satellite
image, or aerial photograph from one coordinate system
to another by using a set of control points and a
transformation equation”.
Transformation involves: scaling, rotation,
translation, and skew a dataset to a given set of
geographic or projected coordinates
3 steps in geographic tranformation
Step 1 updates the control points to real-world coordinates. Step 2 uses the control points to run a transformation. Step 3 creates the output by applying the transformation equations to the input features. h
Transformation methods are distinguished by the _______ properties it can preserve and the changes it allows
the changes could be
change of ____ and ____
change of _____
change in _____ and ______
Many mathematical models (equations)
Each method distinguished by the geometric
properties it can preserve and the changes it allows
The changes could be
Change of position and direction
Change of scale
Changes in shape and size
4 Commonly used tranformation methods
- Equiarea Transformation allows rotation and
preserves shape and size - Similarity Transformation allows rotation and
preserves shape but not size - Affine Transformation allows angular distortion
but preserves parallelism - Projective transformation allows both angular
and length distortion. So a rectangle to be
transformed into an irregular quadrilateral
EAT SAUSAGES AT PRISON
______ transformation method is most
commonly use
Affine transformation method is most
commonly use
Resampling of pixel values
Result of geometric transformation of a image is a
new image based on a given coordinate system
New image has no pixel values. These must be
filled through resampling
Resampling refers to filling of each pixel of new
image with a value derived from original image
Various methods exist
3 common resampling of pixel methods
Three common resampling methods:
1. Nearest neighbor resampling:
fills each pixel of the new image with the nearest
pixel value from the original image.
2. Bilinear interpolation method:
uses the average of the four nearest pixel values
from three linear interpolations.
3. Cubic convolution method:
uses the average of the 16 nearest pixel values
from five cubic polynomial interpolations.
NEVER BITE COCKS
Affine Transformation
X = Ax + By + C ……….. (1) Y = Dx + Ey + F ………...(2)
.x, y are input coordinates and X, Y are output
coordinates
.Coefficient C represents translation in the x
direction, and coefficient F the translation in
the y direction
.Coefficients A, B, D, and E are related to
rotation, skew, and scaling
Allows rotation, translation, skew, differential scaling while preserving line parallelism
Affine transformation Allows rotation, translation, skew,
differential scaling while preserving _____ _____
Allows rotation, translation, skew, differential scaling while preserving line parallelism
Affine Transformation properties
the equations requires at least ____ known points to
estimate its six coefficients. Points also known as ____’s
At least ____ known points are commonly used for
reducing problems with measurement errors and to
allow for a least-squares solution
From the ___ ____ ____ (RMS) error value is the
indicator for the goodness of control points that
derives from the least-square equation
The equations requires at least Three known points to
estimate its six coefficients.
The known points are also knows as tics/ground
control points (GCPs)
At least Four known points are commonly used for
reducing problems with measurement errors and to
allow for a least-squares solution
From the Root Mean Square (RMS) error value is the
indicator for the goodness of control points that
derives from the least-square equation.
Polynomial order in transformations
Describe 3 orders of polynomial
- 1st order polynomial (affine)
requires a minimum of 3 displacement links, but should have more
even though 3 gives RMSE=0!
is a homogeneous transformation: only shifts origin, scales and
rotates
straight lines will be preserved - 2nd order polynomial
requires 6 points (displacement links) minimum
is a differential transformation so it “warps” the raster
straightlines on raster may no longer be straight - 3rd order polynomial
requires 10 points minimum
Polynomials are global transformations which strive to achieve a best fit globally or
overall. Only 1st order with exactly 3 points will exactly match control points.
- ___ order polynomial (affine)
- 1st order polynomial (affine)
Root mean square error
The root mean square (RMS) error is a common measure of
the goodness of control points.
It measures the average deviation between the actual (true)
and estimated (digitized or selected) locations of control
points.
The RMS error is derived from the equation:
T OR F
Low acceptable RMS error does not always ensure the data accuracy
T
_____ ______ method is the most commonly used as
resampling techniques that fills each pixel of the new
image with the nearest pixel value from the original image.
Nearest neighbor method is the most commonly used as
resampling techniques that fills each pixel of the new
image with the nearest pixel value from the original image.
Reprojection
Reprojection:
.using data from different projection systems to bring into one system under same
point registration
Registration: bringing to points together that are on different projections/maps but represent the same location
When a map is scanned, an image is divided into individual pixels which are assigned a value based on ________
When a map is scanned, an image is divided into individual pixels which are assigned a value based on grayscale (gray colour level- 0 is black, higher #’s are lighter)
For artimus error you need _____ control points
4
GIS STORES two types of geographic information : _______ and ______
attribute
features
The functions of a GIS are _______, geodata _______, and geographic ________
visualization, management, analysis,
Geographic Data vs Data
(a collection of) facts about a geographic entity (Earth’s physical features, inhabitants, and phenomena) from which conclusions may be drawn
a collection of facts from which
conclusions may be drawn
Geographic Data model
the methods of representation of
geographical data into the computerized
geographic information system.
• The location of a geographic entity is linked
to a geometry (point, line, poly, or a pixel),
which refers to as spatial data.
• Then the geometry is linked to its attribute(s).
• An attribute could be quantitative or
qualitative.
Geographic data can be ______ or _______ data
spatial(features) and Attribute data
spatial–>Qualitative and Discrete
Attribute data–>Quantitative and Qualitative–>discrete and continuous
What is a node?
What is a polygon?
Nodes: connect multiple lines (start node and end node)
Polygon: all the lines connect together and enclose a shape
Continuous vs Discrete:
- Elevation
- Aspect
- Land Use
- Rainfall
- Vegatation Type
- Pollution
- Roads
- Wells
discrete: Land use, Vegetation type,
Roads, Wells
Continuous: Elevation, Aspect,
Pollutions, Rainfall
Spatial Data is split in two: _____ and ____
raster and vector
Vector Data model
- it uses points and their coordinates to
represent spatial features as points, lines, and
polygons
Dimensionality and property distinguish the
point, line, polygons - it organizes geometric objects and their spatial
relationships into digital data files that
computer can access, interpret, and process
Features are generally represented in Coordinates are most often pairs (x,y) or triplets
(x,y,z, where z represents a value such as elevation).
Describe Point, line , and Polygon
Point
•No length, width or height, only location implied
•Defined by x, y coordinates
•Also called a node or vertex
Line
• defined by a set of connected points
• One-dimension, length, determined by the
distance between the end points
• Lines also known as edges, links
• Examples: roads, streams, contour lines
Polygon
• Two-dimension, length and width give area and
perimeter
• Boundary is defined by a set of lines
• Examples: political entities, water bodies
Raster Data Model
Cell - also known as pixel Cell value , Cell Size Rows, number, Columns, number Number of bands Attribute table in raster dataset
Raster data represent
points by a single cells,
lines by sequences of neighboring cells,
and
areas by collections of contiguous cells.
Some raster datasets contain attribute tables Typically cell values can represent or define a class, group, category, or membership
E.g.: a satellite image may have
undergone a classification
analysis to create a raster
dataset that defines land uses
Cell values can be Integer or Floating-point
In _____ data model what is integer and floating-point?
Integer: Number with no decimal digits Used for represent categorical data or discrete data e.g.: land use, forest category, soil type
Floating point: Number with decimal digits Used to represent continuous data Require more computer storage space e.g.: precipitation, slope, DEM
4 types of attribute data
1.Nominal
• data are qualitative only,
• no computation possible
. no data order
2.Ordinal
• qualitative or quantitative,
• represent an order of the
individuals
3.Interval
• quantitative only
• a zero entry simply represents a
position on a scale
4.Ration
• Interval type with a meaningful zero entry
• a ratio of two data values can be formed so one data value can be expressed as a ratio of the other.
NEVER ORDER INDIAN RICE
Metadata
The term refers to any data used to aid the
identification, description, quality, reference
information, entry information, distribution
information and data authority, etc. of geospatial
data.
Topology
Topology is a mathematical approach of
studying those properties of geometric objects
that remain invariant under certain
transformations such as bending or stretching.
i.e. topology remains constant through
distortion
When a map is stretched or distorted, some
properties of objects are changed:
Distance, Angles , Relative proximities
Some properties won’t change, Adjacencies and incidence Spatial relationships, such as "is contained in", "crosses" Types of spatial objects - areas remain areas, lines remain lines, points remain points These unchanged properties are called topological properties.
Topological Data and GIS
a spatial database is often called “topological”
if the topological relationships have been
computed, stored, and maintained. Such as,
connectedness of links at intersections
ordered set of lines (chains) forming each
polygon boundary
adjacency relationships between areas
Evolution of Vector Data
Model by ESRI systems In “Georelational Data Model” and “Object Oriented data model”
Describe all 4 within these two models
Georelational Data Model: First two
1980’s: PC Arc/Info Workstation Arc/Info began with a coverage data format
1990’s: ArcVIEW then used ‘shapefile’
Object Oriented data model: These two
2000’s:ArcGIS 8 & 9 then started using geodatabase
2010: ArcGIS 10.x continued with geodatabase
Georelational Data Model- coverage
Based on the georelational data model, an Arc/Info
Coverage has two components:
A set of graphic files for spatial data and
A set of INFO files for attribute data.
The label connects the two components through feature ID.
“Coverage” is the name of a GIS data layer in ESRI Arc/Info
data structure.
A “Coverage” in Arc/Info data structure is like a Folder, that
contain a number of files.
Some of the files represent spatial feature geometry,
Some files for attribute data, and
some others for holding other information, such as maximum
spatial extent, annotation, projection parameter, etc.
“Coverage” maintains topological properties in spatial data
structure
collection of multiple ‘coverage’ is called a __________
workspace
what is a tic file?
Tic file= use to pinpoint where info came from
Shapefile
Also known as ESRI ArcView Shapefiles.
Geographic features in a shapefile is also
represented by points, lines, or polygons (areas)
File-based based data
collection of graphic and info files
same file name but different extensions (suffixes)
The workspace may also contain dBASE tables,
which can store additional attributes that can be
joined to a shapefile’s features.
Geodatabase
3 feature geometry types
Geodatabase data model is an Object-based
data model
The Geodatabase model is a collection of
objects, properties and methods held in
a common file system
a Microsoft Access database
or a multiuser relational database
e.g.: Oracle, Microsoft SQL Server, or IBM DB2
Point feature: represented as single point
or multi-point set of points
Polyline feature: a line or a set of line
segments, which may or may not be
connected.
-User-shaped, Curves, Single / multi-part
Polygon feature: a set of one or many rings.
a ring is a set of connected, closed, nonintersecting
line segment.
-Single / multi-part
Polyline vs. line
-polyline feature instead of line because it can be a set of line segments which may or may not be connected
.lines all have to be connected somehow
