gis Flashcards
Data that involves an aspect of location on the Earth’s surface or near-surface, which is converted to a form that is meaningful to a user.
Geographic Information
A computer system that analyzes and displays geographically referenced information. (USGS)
GIS
Data having implicit association with a location relative to Earth.
It includes information such as location of geographic features, different kinds of vegetation, and different kinds of soil.
It can also include information on man made features like farms, schools, roads and electric power lines.
Geographic Information
A system of hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modeling, and display of spatially-referenced data for solving complex planning and management problems. (Rhind)
GIS
Set of computer-based systems for managing geographic data and using there data and using these data to solve real-world spatial problems.
GIS
Why is GIS important?
- Integrate data from various
1. Sources
2. Formats - To come up with more accurate and timely decisions
- Faster analysis
Paper map - static; snapshot of real world at a given time only.
Conventional Data
dynamic; allows a range of functions for storing, processing, analyzing, and visualizing spatial data.
Digital Geographic Data
5 Components of GIS
- Hardware
- Software
- People
- Methods
- Data
Computer system on which the GIS software will run used for acquisition, storage, analysis, and display of geographic information.
Hardware
Provides the functions and tools needed to store, analyze, and display geographic information.
Software
Core of GIS
Data
GIS Data Sources
- GNSS: Global Navigation Satellite System
- Databases: tables of data
- RS & Aerial Photography
- Digitized and Scanned Maps
- Field Sampling of Attributes
- Field Survey Measurements
GIS users range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work.
People
Various techniques used for map creation and further usage for any project.
- Models to come up with the desired products.
Methods.
Representation of the real world geographic features in a digital form to be stored in a GIS database.
Geographic Data Models
2 Geographic Data Models
- Field-based model
- Object-based model
The world is a continuous field in 2 or 3 dimensions (ex. elevation, soils)
Field-based models
Well-defined boundaries such as buildings and roads
Discreet
Diffused boundaries such as forest and beaches.
Fuzzy
Area is covered by grid with (usually) equal-sized, square cells containing an attribute value for each cell.
Raster
Features in the real world are represented either as points, lines, or areas (polygons).
Vector
Spatial relationships between geographic features.
Topological Relationsips
3 Elements of Topology
- Adjacency
- Containment
- Connectivity`
Software designed to organize the efficient storage, manipulation and access to data within an integrated database
Database Management System (DBMS)
Contains geographic data of a particular subject for a particular area.
Geographic Database
A collection of tables or relations that can be connected to each other by keys.
Relational DBMS
Spatial Analysis Process
- Data Gathering / Acquisition
- Pre-processing
- Analysis (Main processing)
- Map Generation/ Visualization
- Decision Making/ Planning
- Applied to the Real World / Evaluation / Validation
Manipulation of spatial data into various forms to be able to extract additional meaningful information to understand the real-world.
Spatial Analysis
Aimed at identifying and describing the pattern and identifying and understanding the process.
Spatial Analysis
A GIS operation that superimposes multiple data sets together for the purpose of identifying relationships between them.
Creates a composite map by combining the geometry and attributes of the input data sets.
Overlay
Mathematical / logical operators are performed on corresponding cells from one or more layers to produce an output value for subsequent analysis.
Raster Overlay
Combine two or more maps based on a set of logical relationships
Logical overlays
Involves a focal cell and its surrounding cells
Neighborhood Operations
To predict values for cells from a limited same data points.
Interpolating to raster
Each sample point has a local influence that diminishes with distance.
Pertains to how sample points have influence diminishing with distance.
Inverse Distance Weighted (IDW)
Vector Operations
- Querying
- Buffering
Performed to select features that satisfy a set of criteria based on the attributes.
Querying
Creation of a zone of interest around an entity.
Buffering
Computes a geometric intersection of the input features. Features of portions of features which overlap in all layers and/or feature classes will be written to the output feature class.
Intersect (AND)
Computes a geometric union of the input features. All features and their attributes will be written to the output feature class.
Union (OR)
Features or portions of features in the input and update features that do not overlap will be written to the output feature class.
Symmetrical Difference (EXCLUSIVE OR / XOR)`
Creates a feature class by overlaying the input features with the polygons of the erase features. Only those portions of the input features falling outside the erase features outside boundaries are copied to the output feature class.
Difference / Subtract / Erase (AND NOT)
Computes a geometric intersection of the input features and identity features. The input features or portions thereof that overlap identity features will get the attributes of those identity features.
Identity
Uses a polygon boundary to cut features and their attributed from a feature class.
Clip
The input feature geometry is replaced by update layer. The attributes and geometry of the input features are updated by the update features in the output feature class.
Cover / Update
Generalizes features by combining features based on a specified attribute/s.
Dissolve
Combines multiple input datasets into a single, new output dataset. This tool can combine point, line, or polygon feature classes or tables.
Append / Merge
Joins attributes from one feature to another based on the spatial relationship.
The target features and the joined attributes from the join features are written to the output feature class.
Spatial Join
A way of constructing a surface from a set of irregularly spaced data points.
Adjacent data points are connected by lines to form a network of irregular triangles.
Triangulated Irregular Network (TIN)
Analysis in GIS
- Query and Overlay analysis
- Proximity analysis
- Suitability analysis
- Hydrology analysis
- Network analysis
- 3D Visualization and Surface analysis
