GIS
database management system capabilities
data model, data load, recovery, index, admin tools, query, security, apps, command line, updates
interval data
data on a fixed interval scale, where there is no true zero point: eg, temp, calander year
ordinal data
data with a specific order or rank, eg #1, #2, #3..."
another word for projection surface
developable surface
nominal error
difference between GCPs chosen and the correct points
Trinagulated Irregular Network (TIN)
digital representation of surface morphology, built off nodes forming triangles
GPS measures...
distance from user to satellite (light-speed signals, time * speed of light = distance), time for radio signal to get from satellite to user
distance property (equidistant)
distance is preserved along particular lines
nominal data
distinguishes one entity from another, all contents are equal: eg farmers name who collected the data, driver's license #
gnomonic stereographic projection
distortion is pronounced
types of scanners
drum scanners (commercial use), slide scanners (for slides), handheld wands (poor quality but useful), flatbed scanners (common kind), digital camera
continuous data
eg. elevation, precipitation (generally raster)
discrete data
eg. houses, roads (generally vector)
hypsometric info
elevation-based
reducing GPS error
fixed GPS station at a known location, record the microwave signals as distance changes b/w you and the satellite (very technical)
types of GIS output
graphs, tables/lists, directions, maps
cluster
group of computers connected in a local area
color shift
innate or occurs over time
GPS noise
irregularities in the transmit signal or receiving system, will cause a small deviation from your actual location
CPU
central processing unit
relational database
collection of tables connected to each other by specific variables
database
collection of tables in digital format
object database management system
complex features with multiple attributes
isoline
connects points with equal attribute values
choropleth maps
constructed from values describing the properties of non-overlapping areas, such as countries or states
flat file
contains all data in a large file (Excel)
GPS blunders
control segment mistakes, software/hardware failures, causes distortions of 100s of km
location of the master GPS control station
Colorado
setting up scanner for archival storage (DPI)
1200
setting up scanner for print (DPI)
300-600
central meridian's easting
500,000 m (false easting)
satellite orbital planes are inclined "x" degrees with respect to the Equator
55
satellite orbits separated by "x" degrees
60
standard scanner resolution
600 DPI
image editing software
Adobe Photoshop (or Elements), GIMP, Corel Paint Shop
vector-centric, closed-source program
ArcGIS
UTM (Universal Transverse Mercator)
Earth is divided into zones (on a flat surface), each zone is 6 degrees wide, has a central meridian
northern hemisphere northing (UTM)
Equator is 0, all northings are greater than this (so a northing of 5,000,000 m is 5,000,000 m from the Equator)
southern hemisphere false northing (UTM)
Equator is given a false northing of 10,000,000 m and all others are less than this
NAVSTAR
GPS constellation, 24 satellites
raster-centric, open-source program
GRASS
Geographic Coordinate System
Lat-long system; 1 degree= 60 minutes= 3600 seconds
geometric transformation
can correct for bends, errors in entering
network
a figure made up of points (vertices) connected by non-intersecting lines (arcs)
relational database management system
a set of tables containing attributes (Excel)
spheroid
a spherical representation of the Earth
direction property (azimuthal)
all directions are shown correctly relative to a center
datums
an estimate of flattening at the poles, defines the position of a spheroid relative to the center of the Earth
Tuple
an individual row/record in a database table
2 properties that cannot be preserved simultaneously in a projection
angles and area
azimuthal stereographic projection
angles are preserved
keys
any attribute or set of attributes whose values uniquely identify each record
equal-area property
area should be preserved on projections
potential sources of error: GPS
buildings, heavy tree canopy, few satellites in view or bunched together, reflection, limited view of sky
network database
builds connections across tables
calibration panels
calibrate scanners for innate colour shift
grid
loose cluster, connected over the internet
why save files as TIFFs?
lossless and will not add artifacts, universal format, can be compressed
Ground control points can be derived from...
manually entering data, GPS, another image, autorectification (algorithm guesses GCP between images)
RAM
moves data from CPU to harddrive, temporary storage
Terrain dataset
multi-resolution TIN-based surface
resampling raster data (shifting)
nearest neighbour, bilinear interpolation, cubic convolution
attribute
non-spatial info about a geographic feature, usually stored in a table and linked to the feature with a unique identifier
ratio data
number data where there is a true zero point: eg, area
hierarchical database
organizes the data at different levels using 1-to-many association (Windows explorer)
normalization
organizing data to minimize redundancy
vertices
other points present in a poly-line or polygon that are not the beginning or end point
portable document format, good to share/print images but not for storage
globe used for a projection
reference globe
topology
relationships that stay the same even if the object is stretched
object oriented data model
represented by shapes
meanings of "scale"
resolution, spatial extent, scale of a map
GPS bias
slowdown of radio signals caused by the ionosphere/troposphere, ground reflection, errors by the satellite, causes greater distortion
conformal property
small features should be preserved on projections
node
the beginning or end of a point, line, poly-line, or polygon
azimuthal/planar projections
touching the Earth with a flat sheet of paper (Lambert Azimuthal Equal Area), good for global views, preserve true direction
isopleth maps
used to visualize data conceptualized as fields (measured on an interval or ratio scale)
parallel computing
useful for complicated problems
assisted GPS
using cell towers to improve GPS accuracy
bathymetric info
water depth
conic projections
wrapping a cone around the Earth (Albers Equal Area, Lambert Conformal Conic), good for E-W areas
cylindrical projections
wrapping a cylinder around the Earth (Transverse Mercator), good for N-S areas
problems with JPEG
you lose data, adds artifacts
