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79 Cards in this Set
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Types of vector data analysis

buffering, overlay, distance measurement, network analysis


Most common analysis of spatial data is what:

buffer and overlay


buffereing is:

creating a proximity area around a selected point line, or polygon


what is a buffer zone

the newly created area within a specified distance from the selected features


A buffere is a:

polygon created at a specified distance from a point line or polygon


a buffer around a point is:

circular zones


a buffer around a line is

elongated polygons following the line feature, the polygong doenst' have to be on both sides of the line


a buffer around a polygon is

a zone extending outward from the polygon boundaries


Buffer issues:

1 you never want to forget the untits youw ant to use,
2 dissolving vs. not dissolving 3 use of different buffer distances 4variation of buffere distances 5multiple buffer zones 6inclusions zones vx. exclusion zones 

What is dissolving:

removing intersects of buffer zones so it is one seamless polygon feature


what is overlay:

MOST POWERFUL feature of modern GIS.
It is the ablitly to place the cartographic representation of a thematic information of a selected theme over that of another 

what is site suitablitly?

examines social, economic, physical, biological and other criteria to locate potential sited for some purpose (part of overlay)


what do overlay opperations combine:

geometry and attributes of two feature maps to create an output


Overlay procedure requires:

an input map layre and an overlay map layer


what can an output layer be in overlay:

point, line, or polygon layer


what must the overlay map layer and input map layer have in common:

the same coordinate system


The input layer can be what:

a point, line or polygon


The overlay layer must be a what:

a polygon ***


type of overlay polygong operations:

1 pointinpolygon
2 lineinpolygon 3 polygoninpolygon 

What are the common overlay methods:

union, intersect, and identity


Union overlay method is what:

OR
both input/overlay =polygon layers combines the area extent from both maps 

Intersect overlay method is what:

= AND
preserves only features that are within common area output feature have attribute data from both layers input layer can be a layer of point, line or polygon 

Identity overlay method is what:

= OR and AND [(Input layer) AND (overlay layer)] OR (input layer)
preserves features that are within common area and features from input layer input layer can be a layer of point, line or polygon 

Buffers can be combined with what to analyze spaitail information:

polygon overlayes


What is vector line length:

length of straight line calculated by pythagorean theorem using beginning and ending point locations
length of curvillinear line calcultaed by adding lenghts of individual line segments uses coordinate system to figure out measurements 

To calculate area of vector polygon you:

break complex polygon into simpler geometric shapes such as right triangles and rectangels whose area can be calculated


Map manipulation is what:

no attribute data combination, just about the geometry


Examples of map manipulation are what:

dissolve, clip, merge


Map minipulation clipping is:

cutting out a section of city (cookie cutting) ex. you could get jsut the roads of the city


Map minipulation merging is what:

seamless layer, erase


Raster data analysis is based on what:

based on cells and grids


Raster data analysis can be performed on what:

individual cells
a group of celss an entire grid a set of grids 

Common Raster data anaylsis operations:

local operations
neighborhood operations zonal operations distance measurements 

What do you have to do before starting a raster data analysis:

set up the environment covered by the analysis


TO set up the env. covered by the analysis you can:

difine the extent of the environment (area extentArcView) (set window ArcInfo)
Define the size of the output grid cells (the size of the input grid cells) (set cell (ArcInfo)) 

What is a mask grid in raster data anaylsis:

a grid (or set of grids) used as a way to difine the area extent of the analysis
in that case the extent of the analysis is defined by the cells of the mask grid that do not have a value of "no data" ("no data" is different from the '0' value) 

Raster data anaylsis common operation: LOCAL OPERATION

core raster data anaylsis
consists of cellbycell operations based on preset or made up functions 

Local operation: types of functions include:

arithmetic
logartithmic trigonometric power *applied by one cell at a time *can be applied on single grid or with multiple grids 

Local operations with a single grid:

each cell value in the output grid is the result of the mathematical operation using the corresponding (overlapping) cell value in the input grid
ex. floating point grid to integer grid slope in percent to slope in degrees universal soil loss equation 

Local operations with several grids;

similar to vector overlay anaylsis
allows more possiblities for local operations ex. the combine operation (several grids) 

Raster data anaylsis common operation: NEIGHBORHOOD OPERATIONS

involves a focus cell and a set of cells in its vicinity (neighborhood)
the value of the focus cell is computed with the values of the selected neighbor (surrounding) cells the selection of surrounding cells is based on the distance &/or the directional relationships to the focus cells the operation may or may not use the focus cell value 

Some neighborhood operations:

* xbyx window = (ex. 3x3) the focus cell is always in the middle (most commonly used)
circle neighborhood= figure out radius of circle & figures out the cell values inside circle Annulus = (doughnut shaped) cells that fall into the doughnut are used for computaion wedge neighborhood= cells insde the wedge are used. ex. data simplification and terrain analysis 

Raster data anaylsis common operation: ZONAL OPERATIONS

*operation used to describe the geometry of zones (in a single grid) or to summarize the cells values by zone.
zones, disconnected zone, continuous zone 

a zone is:

connected (continous zone/1 region) or disconnected groups (2 regions)of cells with same values


Characterisitcs of zonal operations:

zonal operations are performed either on a single grid (discription of zone geometry) or on two grids (summary of cell values by zones)


Description of zone geometry (on single grid)

area is the sum of cells times cell area
ex. cell size = 2m => Cell area = 4msquared 

Zonal operations perimeter:

it is the sum of the lengths of the boundary of each region of the zone
ex. cell size =2m Zone B : perimeter = 2x10=20m (you get 10 by counting the sides of the cells you want to caluculate) 

Zonal operations thichness:

radius (in cell length) of the largest circle that can be drawn within each zone


Zonal operations centroid:

consists of the parameters of the ellipse that best approximate each zone: centroid, major axis, minor axis
(major axis is the longest one, centroid is point in middle, minor axis is the smallest) 

Using operation syntax to summarize cell values by zones (on two grids) you:

used input, zonal operator, and zonal grid to get an output grid


Raster data analysis common operation: DISTANCE MEASURE OPERATIONS

extended neighborhood operation or global operation
it consists of calculated distances away from source cells in a single grid 

Princle of distance computation:

it is based on the nodelink relationship
*node is VERY import. for computation  there are diagonal link, and lateral link , reference cell and direct neighbor cells 

Princle of distance compuation:

its node represents its center
its links are the segments connecting its node to the nodes of the adjacent celss direct neighbor is a cell connected on the side (lateral link) diagonal neighbor is a cell connected by its angle (diagonal link) 

Line Length (raster)

from node to node (not side to side)


Physical distance measure of application of distance measurment operations:

straightline distances away from source cells (similar to a buffer or source cells with continuous distance ex. buffer around stream network)
reclassification=> discrete/homogeneous zone slice operation => equalarea/equalinterval zones) Allocation (allocaion grid, watershed) 

Raster Anaylsis tools: overlays

called Map Algebra (you can +,  , / ) can make use of more than 2 layers


another name for terrain:

land surface


Land surfaces are:

undulated, continuous, and 3D
they are measured and anylays generaged from elevation data 

elevation data of land surfaces include:

slope(rate of change in elevation0
apect (orientation of slope) watershed stream network flow accumulation 

The Z value in terrains:

represent the elevation data in GIS
they are not stored as part of the coordinate system, but as attribute data (vector data z value sotred in numerical field of attribute tabel, in raster data z is stored as cell values in grid) 

Common data for terrain analysis

DEM and TIN
DEM most common input data for terrain anayl. its quality determines the accuracy of the anaylsis needs to be converted to specific software format (grid for ArcView/ArcGIS/ArcInfo) 

Terrain Maping includes:

contouring, vertical profiling, hill shading, hypsometric tinting, and 3D View


Terrain Maping CONTOURING:

ISOLINEline connecting points of equal value in a thematic map
CONTOUR LINE: line connecting points of euql elevationit is the isoline for a topographic map CONTOUR INTERVAL verticle distance between two consecutive contour lines 

Goal of contouring:

gerated contour line or isoline to show the distribution of continous phenomenon


Caseof elevation in contouring:

close contour line=>steep terrain
'V' indicate stream direction (pointing upstream) traditionally helps calculate slope 

Terrain Maping: VERTICAL PROFILING:

construction of diagram showing the change in elevation along a line on a map


Goal of Vertical Profiling:

vizualize the changes in elevation along a linear feature of the map, or along a user difined line


Terain Mapping: HILL SHADING:

it is the simulation of the image of a terrain under the sun light
slope facing incoming light are bright while slopes opposite to the sun are dark 

Goal of Hill shading:

display the shape of lang features


Hill shading is also called:

shaded relief and shading


Terrain Maping: HYPSOMETRIC TINTING

consists of displaying the elevation zones in different colors


Goal of hypsometric tinting:

to visualize the progression in elevation


Another name for hypsometric tinting

layer tinting


Terain mapping:PERSPECTIVE VIEW (3D)

it is the thre dimensional view of the terrain


Perspective View is controlled by 4 parameters:

1) The viewing azimuth angle between north and the line defined by the target (on the surface) and the point of observation=> 0`360`
2)the viewing angle angle between the surface (horizontal) and the line defined by the target (on the surface) and the point of observation=> 0`90` (@90` no longer view it as 3D but as 2D) 3) the view distance distance b/w the ovbservation point and the target 4) the zscale or verticle exaggeration factor ratio b/w the verticle and horizonal scales 

Terrain Mappaing: 3D DRAPING

superimposition of thematic layers with a perspective view


Terrain anaylsis SLOPE:

it is the rate of change in elevation
percent slope= (verticle distance/horizontal distance)x100 degree slope= arctan (verticle distance/horiz. distance) 

Terrain anaylsis ASPECT:

it is the orientation of slope (you can use 0` 360` or cardinal orientation


Terrain anaylsis VIEWSHED ANALYSIS:

*consists of using elevation grids to generate topography related hydrology features such as: watershed and subwatershed, stream network, flwo accumulation (depth)
watershed=catchment=basin DEM=> field elevation=> flow direction grid=> flwo accumulation grid 