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4111-GIS Intro

Geography Information System

TermDefinition
Data has spatial and attribute info to explain where sth is and what sth is
Software is used to store, analyse and display geo data
Hardware Data and software run off hardware
People and Workflows People use GIS to perform GIS task on geo data
Map location Illustrates the location of countries, rivers and cities within the gs continents. Location maps can be used to determine where things are situated in relation to each other and are often used with navigation.
Map quantities Quantitative maps are often used to find trends.
Map what is inside Mapping what is inside can assist with monitoring and assessment.
Map densities Density maps can be used to condense large amounts of data analyzed for correlations and trends. Further analysis could be completed to determine if the denser population is related to the proximity of the border or the proximity of water bodies.
Map what is nearby Mapping what is nearby is often used in risk assessment and predictions.
Map change This can be used to assess future trends in urban sprawl and market demands.
Discover Discover maps, apps, layers, and otehr content from colleagues within your organization, and authoritative content using GIS
Use Use this content to find patterns, gain insight, and conduct analysis
Make If you do not find the content you are looking for, you can make a map or app using existing layers.
Share Share your map or app with colleagues, your organization. Use web maps and apps on browsers and mobile devices, making content available anywhere, anytime and on any device.
Vector Points, Polyline, Polygone
Raster Raster can be used to represent continuous data that does not have distinct boundaries, such as precipitation and elevation.
Raster Data Model represent the feature or phenomena as a grid of cells. Each cell stores a value, and the value can be a discrete value or a continuous measurement.
Raster Location A GIS uses the real world location of the raster, which is known as the origin along with the relative cell location and cell size, to determine the location of the cells and raster on the earth.
Points Points are a single XY coordinate location. Each point has a longitude and latitude location (also referred to as geographic coordinates) that defines the precise location of the feature on the earth.
Polylines Polylines are defined by two or more locations that are connected with lines. Each location has a longitude and latitude (also referred to as geographic coordinates) that defines the precise location of the river on the earth.
Polygons Polygons are defined using multiple locations that are connected and closed. Each location has a longitude and latitude (also referred to as geographic coordinates) that defines the precise location of the lake on the earth.
Shapefile TIFF
CAD JPEG
Geodatabase feature class* Mosaic dataset* *These data types are only available in a geodatabase
Mosaic dataset A mosaic dataset is a collection of multiple rasters that acts as a catalog. The rasters are indexed so that you can easily query and search for the data. A mosaic dataset is a collection of rasters.
Metadata Metadata provides additional information about a feature and its attributes, such as a description of the data, who created the data, and its usage constraints.
The Item Description is one form of metadata that provides some of the basic metadata information and a thumbnail of the feature.
Spatial location in relationship 1- Layer containing features you want to select 2- Location relationship 3- Layer containing the related features
Basic types of location relationships Intersect Near Adjacent Inside
All projections cause distortion in at least one of four spacial properties Shape Area Direction Direction
Mercator Proj Useful for Sailor
Aspect is how the globe is tilted to the projection surface
Perspective is the position of the light source
Gnomonic Light source at the center
Stereoscopic Light source at the antipode
Orthoscopic Light source is infinitely far away
Geographic Coordinate System A reference system that uses latitude and longitude to define the locations of points on the surface of a sphere or spheroid. A geographic coordinate system definition includes a datum, prime meridian, and angular unit.
Coordinate System A geographic coordinate system describes the values for latitude and longitude in three-dimensional space. Horizontal parallel lines show latitude values and vertical meridians show longitude values.
Reference Globe A reference globe is created by wrapping a grid of lines, or graticule, around a model of the earth. Each reference globe is based on a geographic coordinate system, and geographic features are given coordinates on it.
Projected map Using a mathematical formula, features on the reference globe's surface are transposed onto a flat surface. Coordinates on the globe are transformed into XY values on the "projected" map.
Projected map (cont) Therefore, if two projections are based on different coordinate systems, each projection will have a different physical location for the same set of coordinates.
Azimuth The horizontal angle, measured in degrees, between a baseline drawn from a center point and another line drawn from the same point. Normally, the baseline points true north and the angle is measured clockwise from the baseline.
Conformal map A map that preserves shape. Even on a conformal map, shapes are a bit distorted for large areas, like continents.
Isotropic Two instances of spatial auto-correlation can occur. In the first, the relationship between points and their values is determined by the distance between points.
Anisotropic The relationship between points and their values is determined by distance and by direction. For example, prevailing winds and ocean currents can create this effect.
Sill The height of the semivariogram, know as the sill, shows in the variation between data values.
Range is the distance between points at which the semivariogram flattens out.
Horizontal line in semivariogram No spatial autocorrelation. Spatial statistics would not be appropriate to use with your dataset
Data is stationary The rel btw 2 points and their values depends on the distance between them, not their exact loc. Data Var should be consistent across the study area.
Use Voronoi map to explore spatial variation Vironoi map is created by defininng Thiessen polygons
Tessellations groups of polygons that create a surface with no overlaps and no gaps.
Voronoi maps are tessellations in which the polygons are defined as the area that is closer to a data point than all other data point
Thiessen polygons are also tessellation, in which the polygons are defined based on this same principle.
Delaunay triangulation are also related to Voronoi maps. The triangles are transcribed by circles that contain no other dataset points in their interior. The centers of the circles are connected to form the Voronoi map polygons. De tesslations are used to create TINs
TINs Triangulated irregular networks
A simple Voronoi map Shows the data value at each location. Map is symbolized using a geometrical interval classification. This will show the variation in data values across your entire dataset.
A standard deviation Voronoi map displays the local variation between your data points. The SD between a polygon and its surrounding polygons is calculated.
A standard deviation Voronoi map (data not stationary) If a standard deviation Voronoi maps shows very different local variaition across the study area market by areas with values that different local variation across the study area marked by areas with values that differ from the overall SD.
An entropy Voronoi map display local variation btw the data points. Var in an antropy Vor map is cal. based on the class of each surrounding polygon. If an entropy Vor map shows very diffnt local var with higher value, data not stationary.
Data outliers reveal mistakes (input errors),unusual occurences (the population of NY cmpared to the avg US city), and shift points in data patterns (a valley in a mountain range).
Semivariogram cloud Spatial autocorrelation assumes that points closer together will have smaller distances between their values. When points closer together have higher differences in their values, this may indicate an outlier in the data.
Semivariogram selections on the map Each of the selected pounts in the semivariogram cloud represents the relationship beween two points
Voronoi map Cluster Voronoi maps show spatial outliers in the data; simple Voronoi maps can pinpoint data values that are many class breaks removed from surrounding polygons.
Histogram A histogram can also display outliers. Values in the last bard to the left or right if far removed from the adjacent values, may indicate outliers.
Normal QQ plot Values at the tails of a normal QQ plot can also be outliers. This can happen when the tail values do not fall along the reference line.
The number of lags define the distance that you will investigate in semivarigram cloud. will change the lag size to the average distance between neighboring weather stations.
Zoom the semivariogram where spatial autocorrelation is most likely to exist.
Created by: BelleNg