ENR 3700 Exam
Direction
"where's north"
What are coordinate systems?
A frame used to define the locations of geographical entities using some coordinate values (x,y)
Discrete data
Are distinct features that have definite boundaries and identities (Vector)
Geoid
As a very bumpy, irregular surface with equal gravity (the actual shape of the earth)
What are the two components of spatial data?
Attributes and location
ancillary information
Author, date (when map was made), location of map file(s), and supporting data, source data and projections, map maker, data sources, legal considerations
Continuous data
Has no define borders or distinctive values, instead, a transition from one value to another (raster)
What is the spatial information flow?
Collection --> GIS --> cartographic presentation (maps) also how we lie
Observational data
Observe subjects and measure variables of interest without assigning treatments to the subjects. That treatment that each subject receives is determined beyond the control of the investigator
primary data
first hand data gathered by researchers themselves
Global (map algebra)
one value for entire image is computed
Point of Origin
point where earth and ellipsoid align
Visualization of vector
points, lines, polygons
Examples of vector data
points, lines, polygons, Triangulated irregular networks
Mixed Pixel Problem
Some cells may encompass two or more features and only one may be marginally dominant and that is what is represented on the map
What are some problems with using coordinate systems?
There are 1000s of different systems each giving slightly different answers
How do we define a place on earth?
With coordinate systems or use the US Public Land Survey System
*Reclassification* Could we use this on the DEM file?
Yes We took the information we needed from the .zip file and further altered this data to show specific locations on our maps (same as NLCD)
*Reclassification* Could we have used this in the NCLD data from the lab?
Yes, by going to the NLCD website and renaming the colors that they associated with various land features both natural and man-made.
Very small scale
above 1: 250,000
Advantages of Vector Data
accurately represents true shape and size, representing non-continuous data, conserving disk space
examples of raster data
aerial imagery and digital elevation models
Color
affects interpretation
Relationship between data and information
collection of details about something that is vital for another process
Disadvantages of Vector Data
complex data structures, simulation may be difficult, spatial analysis can be difficult or impossible
Orientation
position of the ellipsoid
How do geographic and projected coordinate systems compare?
projected coordinate systems determine absolute location
Projected Coordinate System simply called
projection
Scale
representations of map figures to their ground equivalent
Four types of distortion
shape, area, distance, direction
Advantages of Raster Data
simple data structure, easy overlay, various kinds of spatial analysis, uniform size and shape
Local (map algebra)
single pixel calculation
Large scale maps cover ____ areas
small
Data source
source and data for both the geographic data and attribute data
Reclassification
strategic placement of an object, person, or idea under a new heading taking someones information and map algebra and making it useable for yourself.
Attributes
that describe phenomena, processes, and characteristics for feature or entities on earth
Location
that tells where the features and entities are on the earth or in our environment
What is map algebra?
the cell by cell combination of raster layers
Information
the organization of DATA such that it is valuable for analysis, evaluation, and decision making
Focal (map algebra)
use a neighborhood to change a single pixel
Zonal (map algebra)
uses map constraints to change pixel value
5 key strategies for interpreting maps
who is using the map, who is making the map, the purpose, the content, the scale
What does GIS stand for?
Geographic Information System
Best solution for the mixed pixel problem?
Winner take all
How is raster data stored?
.jif, .tif
How is vector data stored?
.shp, .shp.mxl (metadata), .dbf, .prj
Visual Balance
- The size of symbols - The pattern of the symbols - The color of the symbols - The visual hierarchy of the symbols and elements - the location of the elements with respect to each other and the visual center of the map
How is GIS used?
- Used to manage, analyze and present information - used to navigate - used to understand spatial phenomenon - used to explore the world near us - used to better manage the world around us
What are the three questions you need to answer before making a map?
-The people who may use the map (the audience) - The objective(s) of the map (the message) - The data that will be displayed in the map (the information available)
Small scale
1: 10,000 to 1: 250,000
Which is the larger scale map: 1:100,000 OR 1: 24,000
1: 24,000
Medium-scale
1:1,000 to 1: 10,000
Large scale
1:250 to 1:1,000
Projected Coordinate System
2D, projection, classification of projected coordinate system, planar
Geographic Coordinate System
3D, understand the shape and geometry of Earth, define the concept of datum, latitude and longitude
Datam definition
A mathematical model that defines and standardizes the shape of the earth including three elements
Ellipsoid
A model to approximate the shape of a geoid (earth) A sphere that is smushed down in the middle
Location Inset
A smaller more zoomed in section of the map (think of what we made during lab 4)
Common non-GIS ways to establish location
Come here, see you there, street, road, city etc.
What is the first principle of Krygiers 5 principles of map design?
Concept before compilation. You need a full concept of the map before you can make it (who, why)
Shape distortion
Conformal- shapes are distorted, depicted too small or too large On Earth: regular square On Map: distorted square (stretched, etc.)
Three elements of datum
Ellipsoid, Orientation, Point of Origin
Contrast
Emphasizes what information you want to be gleaned from the map
What is the fifth principle of Krygiers 5 principles of map design?
Engage the emotion to engage the understanding
Area distortion
Equal area size- preserves area, size on map is relative to size on earth On Earth: normal rectangle On Map: stretched rectangle
Distance/ scale
Equal distant- preserves true scale for all straight lines passing through a point On Earth: regular line On Map: Extended line
People associate colors of mapped features with ____, emotions and ______
Events/ socioeconomic status
Tobler's First Law of Geography
Everything is related in someway to everything else, but near things tend to be more related than distant things
What is the second principle of Krygiers 5 principles of map design?
Hierarchy with harmony the important things should look important but the unimportant things should be there to complement the important (what is important)
What is GIS?
It is a computerized system (most recent adaptation) used for assessing spatial info
What are the layers for map algebra?
Local Focal Zonal Global
What is the fourth principle of Krygiers 5 principles of map design?
Maximum information at minimum cost, how much information can be gleaned from the map at just a glance
Legend
Needs to clearly define the category break
Title
Needs to clearly define what, where, when is being mapped, prominently
Vector Data
Provides a way to represent real world features within the GIS environment. A feature has its shape represented using points, lines, and polygons, and TINs
Using reclassification and DEM, can you think of a data flow to go from a raster DEM to contour polygons?
Raster dem's are elevation data. Contours are vector lines showing elevation contours. So all elevations between 600 and 610 are bounded by a 600 and 610 contour lines. All raster values between these two lines are between these two numbers.You could test for values to be between 600 and 610 and give them one value. Likewise for all other intervals. That is how you get from a dem to a contour line. *this is off someone elses thing b/c i had no idea*
Topology
Set of rules that defines how point, line, and polygon features share coincident geometry. Describes means, whereby lines, borders, points meet up and cross.
What is the third principle of Krygiers 5 principles of map design?
Simplicity from sacrifice not what you put into the map but what you take out of it (less is more)
What elements of mapmaking are considered art?
Symbology , visual balance, color, and contrast
Visualization of raster
Table of pixels where each pixel is assigned a different value.
Annotation
Text that adds meaning to mapped features
Symbology
The art of expression, using graphics and text to convey meaning
How do maps lie?
They are subject to bias and only present certain information instead of all information
Why is topology important?
Topology keeps us from using bad data. When the rules of topology are violated, we cannot build. Important to GIS because it allows for functions like routing, stream flow, and traffic studies as well as allowing for automated error detection, elimination of error, and sharing features
Do larger scale maps show more detail than smaller-scale maps T/F
True
T/F A datum is REQUIRED to define any coordinate system
True
Projection coordinate systems we have used
Universal Transverse Mercator and Stane Plane Coordinate System
Neat Line
a box drawn around the map to give a "neat," or tidy, appearance to the product
Data
a collection of attributes, facts, measurements or statistics about entities
Experimental Data
apply treatments to experimental units and the proceed to observe the effect of the treatments on the experimental units
Direction/ angle
azimuthal measure in degrees fo angle from north, preserves direction On Earth: regular angle On Map: extended angle
Raster Data
cell or pixel based data
Metadata
data about data- all the facts you need to know about your data set
Secondary data
data collected by someone else earlier and re-used for other purposes
Definition of spatial data
data/information that identifies the geographic location of features and boundaries on Earth
To define a GCS, a ____ must be first chosen
datum
Disadvantages of Raster Data
large amount of data, less "pretty", different scales between layers
Geographic Coordinate System simply called
longitude and latitude