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46 Cards in this Set
- Front
- Back
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Spatial Analysis
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1: application of operations to coordinate and related attribute data
2:When we manipulate our spatial data in some way in order to solve a problem or identify specific regions sharing attributes 3: Also includes the manipulations of attribute data |
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Database Management Systems
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- GIS attribute data generally stored in the form of a database
- Database-collection of files and tables - GIS generally uses relational database structure |
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Database Rules
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- Only one value is in each cell at the intersection of a row and a column
- All values in a column are about the same subject - Each row is unique - There is no significance to the sequence of the columns - There is no significance to the sequence of the rows |
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Types of Attribute Data
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-Short integer: -32,768 to 32,768 (2 bites)
-Long integer: -2,147,483,648 to 2,147,483,647 (4 bites) Float: Up to 7 decimal places of precision (4 bites) Double: Up to 15 decimal places of precision (8 bites) Text:Character strings Date |
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Joins
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-Useful to adding attribute data to shapefiles
-Join creates a new field in a shapefile, relate allows you to access attributes without adding field -Must have a common field name --- Combining fields based on common tables -- You must have at least one shared field in order to join successfully -- Shared fields can be created using the "Field Calculator" |
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Selection base on Attributes
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-Definition Query
-Selcect by Atrributes |
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Definition Query
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Removes values that are not included in query
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Select by Attribute
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selects values that are included in query
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Selection and Classification
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-Selection operations identify features that meet on to several conditions
-ex. states larger than 85,00sq. km. |
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Queries
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-Selection features based on attributes, spatial or aspatial
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Algebra based quaries
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uses operations such as >,<, =, to select features
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Boolean algebra based queries
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uses OR, AND, NOT to select features
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Classification
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-Categorizing geographic objects based on a set of conditions
-Can be done through symbology tab or using reclassify tools -Binary classification -Equal interval Classification -Natural breaks -Other types: Quantile, equal area, manual, standard deviation |
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Zonal Functions/Operations
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A spatial operation applied to a zone-group of cells having the same value - ex. Land use type or soil type.
-Zones do not have to be adjacent -Can summarize, calculate statistics, calucalte areas, and more complicated analysis using zonal functions In the last lab we had to calculate the percentage of counties forested. In this case, each county was a zone |
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Neighborhood Functions/Operations
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-A spatial operation where the output location, area, or extent comes from operations on an area larger than, and usually adjacent to the input extent. (usualy a 3 x 3 window around cell)
-used for topographic calculations, averaging data, smoothing data, identifying features from data. |
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Mask
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Defining the area of analysis to a certain irregular boundary. Ex. In the last lab, we specified Centre County for our analysis in Part 1
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Cost Surfaces
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A cost surface, or cost grid, is a raster grid in which the value in each cell is the cost that a particular activity or object would be in that cell. cost could be measured monetarily or in other ways such as amount of time.
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Attribute Data
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Tabular or textual data describing the geographic characteristics of features
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Attribute
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Nonspatial information about a geographic feature in a GIS, usually stored in a table
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Joining
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-- Combining fields based on common tables
-- You must have at least one shared field in order to join successfully -- Shared fields can be created using the "Field Calculator" |
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Relates
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-An operation that establishes a temporary connection between records in two tables using a key/field common to both
-Relates defines a relationship between tables, useful for one-to-many relationships |
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Database Management system
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A set of software applications used to create and maintain databses according to a schema
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Data
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Any collection of related facts arranged in a particular manner
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Table
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A set of data elements arranged in rows and columns, with each column representing a field of the record. Rows and Columns intersect to form celles, which contain a specific value for one field in a record
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Dissolve
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-combines similar features within a data layer
-removes features and attributes for like information -used to simplify information -Usually dissolve on an attribute that you're interested in -Used to remove unnecessary information -Used for display purposes to change the appearance of layers that are available to us |
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Buffer
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creates a region less than or equal to a specified distance from a feature
-Region less than or equal to a specified distance from a feature -We can create buffers for VECTORS like points, lines, or polygons |
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Clip
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-An overlay function
-cookie cutter overlay-bounding polygon deines the boundaries for the "clipped" data layer |
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Intersect
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- Overlay function
-combines data for layers where both layers contain data-features from bounding layer and data layer are combined only where the layers overlap |
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Union
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-an overlay function
-joins all data from bounding and data layer |
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Merge
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combines multiple input datasets of the same data type into a single, new output dataset.
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Local Operations/functions (raster analysis)
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-A spatial operation where the output location, area, or extent comes from operations on that same extent.
ex. 1 cell plus 1 cell covering the same location Cell-by-cell combination of raster data -Unary operations -Binary operations -Map Algebra -Reclassify -Extent -Resample |
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Map Algebra
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-Application of computational functions to spatial data
-Requires objects, actions, and qualifiers on these actions -Functions can be applied to individual or multiple layers Outputs can be skewed when layer extents are different - Creates the necessity for extent tool -cateogized into four classes: -Local -Focal -Global -Zonal |
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Reclass
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-Changes individual cell values of a raster data set based on the definitions of a reclass table
-Reclass produces a NEW raster layer along with manipulating the table -Unmateched values can be included in data in a variety of ways (i.e null within range of) -Detail of reclassification is dependent on detail of functions applied -More permanent than simply changing symbology as we've been doing |
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Extent
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-The compete area covered by an individual layer
-Changing extent will rescale layers to match by either... -minimum common points to all inputs - maximum extent of all inputs -specified max and min coordinates |
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Resample
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-Changes the scale of the raster data cells while maintaining orginal extent.
-When resampling raster layers several decisions can be defined -Nearest, majorit, bilinear, cubic |
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Spatial analysis tools
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Queries, clipping, merging, dissolving, buffering, etc.
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Binary classification
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divides objects into two classes, often 1 and 0, prsence absence, etc.
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Equal interval Classification
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Subtracts lowest value from highest and divides remaining numbers into equal categories
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Natural breaks
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looks for obvious breaks or changes in data - default for ArcGIS
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Uses of Raster Data
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-elevation data
-multispectral data -base-map data -Land Use/impervious surface -Temp -Precipitation -Air Pollutants -Any Continuously changing variable |
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Raster Data
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-Vector data primarily ESRI shapefiles - not true for rasters
-Available as many types, many different extensions -Very flexible file format due to ease of coding cellular data |
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Resolution
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-Any decrease in raster cell size results in an increase of data storage by a power of two
-There's a constant trade-off between accuracy and storage capacity |
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Global Functions/Operations
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-A spatial operation where the output location, area, or extnet comes form operations on the entire input area or extent-data comes from the entire layer
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Unary operations
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-Map Algebra local function
-appply to one data layer ex. multiplying the raster by a scaler multiplier. Each value in the raster is multiplied by a number |
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Binary Operations
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-Map Alegbra- local function
-apply to two data layers. -values from different layers may be combined using simple mathematical operations of Boolean logic expressions |
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Kernal Filters
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-type of neighborhood function
-averaging kernals that smooth, remove anomalous data -Edge dection kernels that highlight edges -high pass filters - accentuate difference between adjacent cells- identify spikes and pits in data |
