MIDTERM key terms Flashcards
understand the key terms and see how they connect to GIS and cartography
What is a map?
Maps describe spatial relationships. They are they way we index the landscape, represent and interpret spatial relationships, define places and spaces.
They also act as an assertion of power, and administrative control, explain social, cultural, and environmental processes
What are maps composed of?
Map body, inset/overview map, titles, legend, scale, orientations/direction indicator, map metadata
What is GIS?
GIS = Geographic informational systems
They embody the process of layering information and are a computerized system for capturing, storing, importing, analyzing, and managing data to be spatially references
LINKING LOCATIONS WITH INFORMATIONS
What are GIS composed of?
hardware, software, data, people. Methods, internet
What is the structure of a GIS?
(1) data layer (stores), (2) business layer (manages), (3) display and service layer (synthesizes)
What are the elements that compose a map
Locations and attributes
Locations → positions in two dimensional spaces
Attributes → two types: identity and descriptions (e.g. qualities of quantities ex: city names or population figures)
What is scale?
scale is a ratio of map unions to earth units - with the mpa units standardized to 1. The area is unitless measure. Meaning the scale is consistent regardless of unit of measurement (e.g miles, km, feet, meters
how do you calculate scale?
Scale = map distance/earth distance
What is geospatial data?
there are 2 types of geospatial data: vector and raster
Describe Vector data
Vector → is a representation of the world using points, lines, & polygons. It is a method of storing, representing or displaying spatial data in digital form. It consists of using coordinate pairs (x,y) to represent locations on the earth.
describe raster data
Raster→ images are composed on individual pixels and each square in a image is one pixel
Describe a data layer
vector and raster data are used to compose differnt data layers which are grouped by theme. There is only one themse per layer
What is a feature?
Features are the identifier of each geographic object that composes a layer. Features are linked to rows in the attributes table and can take the form of points lines or polygons. Features have attributes that identify and describe features
What are the basic types of mapping
general reference mapping, special purposes mapping, and thematic mapping
How do we present geographic information on a map
Visual hierarchy → the order in which map element are perceived
Balance → map body vs white space
Contrast & use of color → emphasize or deemphasize certain map features on color selection
Describe thematic mapping
A thematic map shows the spatial distribution of one or more specific data themes for standard geographic areas. They can portray physical, social, political, cultural, economic, sociological, agricultural, or any other aspects of a city, state, region, nation or continent
What are the thematic mapping techniques?
Four thematic mapping techniques:
chloropleth (shaped by unit)
proportional symbol (graph/chart)
isarithmic (lines of equal value)
dot mapping (dots for values)
How do we classify data for thematic mapping
Equal intervals → divisions at regularly spaced intervals
Quantiles → equal number of observations in each class
Natural breaks → classes formed around natural groups of data
Mean standard deviations → considers the mean (average) of the data and calculates how the data deviates from the mean
Manual → DIY classes/make your own
Geometrical interval → minimized the sum of square of the number of elements in each class
What is a geographic coordinate system?
Geo coordinate system → global or spherical coordinate systems such as longitude and latitude
Also known as graticule → latitude (parallels) and longitude (meridian)
What are the types of approximations of earth using spatial data
sphere, ellipsoid, or geoid
What composes a coordinate system?
includes an angular unit of measure, prime meridians, and a datum
Datum → center of the sphere/defined the positions of the spheroid relative to the center of the earth
What are map projections?
→ coordinate systems that provide various methods of projecting the earth’s spherical surface into a two dimensional cartesian (long and lat) coordinate plane
define a developable surface
→ a mathematical definable surface onto which the land masses and graticule are projected from the reference globe
what are the characteristics of all map projections?
Case → related to how the developable surface positions with respect to the reference globe - how it touched the globe
Aspect → the viewing angle deals with the placement of the projections center with respect to the earth’s surface. We can view the earth in three aspects (equatorial, polar, and oblique)
Class → refer to the overall appearance of the graticule once the projections process of complete (this is the cylindrical, conic, and planar classes)
What are standard lines?
Standard lines → indicate the point(s) which the developable surface touches the reference globe
The globe can touch via tangent lines (once) or secant lines (twice)
where these lines touch are where there is the least distortion, the farthest places from these points result in the most distortion
What are the 4 spatial relationships that can be preserved or distorted by map projections
Relationships:
Area, angle (shape), distance, directions
Projections (that can save the relationships):
Equivalent or equal area, conformal, equidistance, azimuthal projections
What is a grid system?
→ a grid is placed over a map projections eyeing a plant or cartesian (x,y) coordinate system to locate features
What are the types of grid systems
Universal transverse mercator (UTM)
State plane coordinate systems (SPCS)
Define model
Model → Idealized and simplified representations of the world
Data model → is a set of constructs for representing object and process in the digital environment without reference to their locations
Spatial data model → a set of constructs for representing geographical objects, data, processes and relationships int e digital environment, for the purposes of analysis and complex problems solving
What is a table?
Tables → are used to organize feature attributes. There is a one-to-one linkage between rows in the table and the spatial data the feature layer
Each feature in the data layer has only one entry in the table. Associated data is held in a relational database system (RDBMS)
what is topology?
Topology→ a set of user defined roles and is the study of the mathematical relationship between points lines (arcs) and polygons. It enables the creation of continuous surface
Define vector
Vector → is a representation of the world using points, lines, & polygons. a method of storing, representing or displaying spatial data in digital form. It consists of using coordinate pairs (x,y) to represent locations on the earth.
define raster
Raster→ images are composed on individual pixels and each square in a image is one pixel. It consists of using cell data arranged in a regular grid pattern in which each unit (pixel or cell) with the grid is assigned an identifying value based on its characteristics. Each cell has an entry in the attribute table .
What is the Procedural modeling process when faces with a problem?
Need to combine different layers of information.
Procedural for modeling process:
1. Identify the problem
2. Breakdown (simplify) the problem into smaller steps
3. Organize the data required to solve the problem
4. Develop a clear & logical flowchart using well defined operations
5. Run the model and modify (calibrate) it if necessary
What is a feature
Each feature has attributes, a feature cna take the form of points lines and polygons and are linked to a row in the attribute table
What are attributes
Attributes consist of a unique identifying key and descriptions.
Each row in the table is unique, columns represent attribute classes, rose represent individual records or observations
What are database keys (any the types)?
Database keys → facilitate the relations in a relations database
Primary keys → unique identifier for EACH row of informations in a data file
Foreign keys → non unique identifier that carries information linked to the primary key. It is used to link formation in another table, and is often the primary key of another RDB
What are structured Query language (SQL)?
SQL → standard computer language for accessing and managing databases
define queries (and types)
Queries → are the primary method of data retrieval. Created new informations from existed info, both dont change the older/existing informations
Aspatial → queries using query algebra [ < > + <> ] => set algebra, [OR AND NOT] => boolean queries
Spatial → retrieving feature bases on their locations: can be done using adjacency or containment
What are relates?
Relates →you relate two tables when the data in the tables have a one to many or many to many relationship
What are joins?
Joins → you want to join tables when the data in the tables have a one to one or many to one relationships
