ppt2 Flashcards
A system for capturing, storing, checking, integrating, manipulating, analyzing and displaying spatial data
Geographic Information System
GIS process
- Input: spatial data
- GIS/mapping software: analysis and data visualization (does not come with its own data)
- Output: new data and maps
Theoretical overview
- GIS creates real world spatial data
- As digitized themed data “layers”
- Assembled in any combination
- And overlaid for analysis
desktop softwares
ArcGIS Pro
QGIS
GIS Applications
View imagery
Create 3d models
Create maps
Conduct analysis
e.g. points, lines and polygons
vector
Composed of coordinates
vector
most common vector file format
shapefile
Actually a collection of several different files with different extensions
shapefile
Rows represent unique geometries (e.g. state polygons)
Columns represent a number of variables (theoretically infinite)
vector Backend database/Attribute table
e.g. row and column matrix
Raster
Composed of pixels
Raster
Includes aerial photographs, digital elevation models, and scanned maps (all constructed from pixels)
Raster
Each cells has its own value
Raster can only symbolize one variable at a time
frontend cell matrix
Rows represent unique values (e.g. 1m, 2m, 3m, etc.)
Columns have specific variables
raster Backend database/Attribute table
Includes common image formats
raster file extensions
spatial data types
vector
raster
tabular
Can be transformed into spatial data in two ways
tabular data
tabular data can be transformed into spatial data through:
joining and geocoding
joining methods
Use a shared unique identifier to match up tabular data to spatial’s data attribute table
geocoding methods
- Use lat/lon coordinates in table to plot as points on map
- Use addresses to plot locations based on a street network
geodatabases
ESRI/ArcGIS storage system
a collection of geographic datasets of various types held in a common file system folder
ESRI/ArcGIS storage system
advantanges of ESRI/ArcGIS storage system
larger files size limits,
faster processing time when using
analysis tools
disadvantages of ESRI/ArcGIS storage system
can only be opened in ESRI software
common associated workflows
- satellite remote sensing
- 3d modeling and photogrammetry
- statistical analysis
- visual design
Processed imagery as rasters or vectors (e.g. enhancements, classifications)
Satellite remote sensing
Raw Imagery for basemaps
Satellite remote sensing
Processed imagery as rasters or models (e.g. orthophotos, DEMS, 3D models)
3d modeling and photogrammetry
Attribute tables for running analyses, (e.g. regressions, predictions)
Statistical analysis
Maps for improved design aesthetics
Visual design
characteristics of spatial data
generalization
abstraction
spatial resolution/scale
temporal resolution
The most detailed data available is not suitable for all purposes (or often a manageable file size)
Generalization
The process of reducing data from its complete state to what is necessary for use and presentation
Abstraction
Suitable data geometry is dependent on scale e.g. roads are polygons at local scale but lines at national scale
Spatial resolution/scale
Searching for spatial data
-Look in general GIS data repositories
-Search the internet
-Include “gis”, or “data” in the search terms Search by location and/or topic Search for country statistical agencies or open data sites (large cities often have their own open data portals as well)
-Contact GIS departments, universities, or researchers in your area of interest.
-Search for articles on your topic and look for the sources of the data.
Used to learn how and why the data were created, access restrictions, columns in the attribute table, and much more!
metadata
data visualization principles
cartography
maps
is the art and science of making maps
Cartography
always simplifications of reality, which makes them helpful when making decisions or explaining patterns
Maps
designed by people (who have intentions), so we have to create them responsibly
Maps
three key questions
- who wants the map
- where will it be seen
- what is its purpose
map design process
-Start with assembling the data from multiple sources
-Choose data, analyses, and symbolization
-Insert the title, legend, north arrow, scale bar and labels
Provides accessible color options
Colorbrewer
Commonly used map type
Choropleth
These use different shading and coloring to display the quantity or value in defined areas
Choropleth
choropleth map choices
-number of classes
-classification method
Aggregates data for display
More classes=more variation
number of classes (choropleth)
Data classification is how data is arranged into separate classes
Classification method
Classification method major types
Equal intervals
Quantile
Natural breaks
Defined intervals
classes have equal ranges
Equal intervals
classes have equal counts
Quantile
optimizes class variation
Natural breaks
you define classes
Defined intervals
Is about developing a balanced arrangement
Map layout design
GPS
global positioning system
Etched the lay of the land in clay tablets
Babylonians 2300 BC
started making maps using wooden blocks
15th century
TIGER:
Topologically Integrated Geographic Encoding and Referencing
Outsourcing tasks to a large group of people often through an appeal on the internet
Crowdsourcing
A free wiki map that allows users to edit and add geographic data
Open Street Map
is an open source software application which utilizes user-generated reports to collate and map data.
USHAHIDI
Text message network used in the Haiti earthquake
4636 effort
