GIS Final

Local raster operations

Changing the values of individual raster cells.

Zonal statistics

Calculates statistics on values of a raster within the zones of another dataset.

Map algebra

Combining map layers using mathematical or statistical operations, also known as raster map overlay.

Neighborhood raster operations

Spatial filtering used to improve the quality or appearance of raster grids.

Low pass/frequency filtering

Used to smooth out local details and emphasize general trends.

High pass/frequency filtering

Used to enhance edges and extreme values.

Slope

In 2D, slope represents the Y differences divided by the X differences between two points; in 3D, it's calculated using a raster cell's neighborhood.

Aspect

The direction that slope faces, measured in degrees.

DEM

Digital Elevation Model; a type of raster data representation of Earth's surface that provides elevation information.

Hill shading

Drawing shadows on a map to simulate sunlight over terrain, creating a 3D effect.

Triangulated Irregular Networks (TINs)

A type of GIS data representing geographic spaces as contiguous triangles, typically in 3D vector format.

Spatial interpolation

Using points with known values to estimate values at other points.

Nearest-neighbor interpolation

Assumes that an unknown point shares the values of its nearest control point.

Thiessen polygons

Voronoi Diagrams; each polygon contains one point, closer than any point in other polygons.

Inverse distance weighting

Assumes a variable's value at an unsampled point is more influenced by nearby known points.

Mode

Most common value in a dataset.

Median

The middle value of an ordered dataset.

Mean

Sum of all values divided by the total number of values in the dataset.

Standard deviation

Shows how much the data varies around the mean.

Statistical distributions

Used to model spatial variability of geographic .

Centroid/mean center

Measure of the center of a geographic distribution, also known as the center of mass.

Median center

Minimizes the distance to all other features as a measure of central tendency.

Standard distance

Measures how features are concentrated or dispersed around the mean center.

Spatial Pattern; Random

Neither clustered nor dispersed.

Spatial Pattern; Clustered

Points are concentrated in groups.

Spatial Pattern; Dispersed

Points are scattered across the distribution and not located nearby each other.

Average nearest neighbor analysis

Describes the overall distribution of a set of points.

Spatial autocorrelation

Measures spatial dependency of geographic data.

Tobler’s First Law of Geography

"Everything is related to everything else, but near things are more related than distant things."

Moran’s I test

Measures overall spatial autocorrelation in a GIS dataset with values from -1 to +1.

Nodes

Represent points or locations in a GIS network, such as intersections.

Edges

Represent the connections or paths between nodes in a GIS network.

Shortest path analysis

Determines the least cost path between nodes using edge weights.

Geocoding

The process of finding a geographic location from an address or text.

Visual hierarchy

Organizes the content of a map to visually communicate order and importance.

Visual cues that create visual hierarchy

Size, position, figure-ground, and color that help in quickly perceiving important information.

Visual variables

Size, shape, color, shade, and pattern elements used in map design.

Figure-ground

Differentiates between objects that stand out (figures) and the background (ground).

Color perception

The human brain perceives colors differently based on context; color choice is crucial.

Colorblind-safe color schemes

Color schemes that are accessible for individuals with red-green color blindness.

Critical map reading

Analyze maps beyond surface level, considering the author's intent and choices.

Ethical implications of geospatial technology

Concerns about personal data trails and potential misuse of information.

GIS code of ethics

Guidelines concerning obligations to society, employers, colleagues, and individuals in society.