Principles of GIS Final

This is directly from quizlet https://quizlet.com/981966758/principles-of-gis-test-3-flash-cards/

Raster analysis can be performed at

• cell level

• Group of cells

• cells within entire raster

output cell size is usually _____ than the largest cell size in the input raster

set equal to or larger

what limits the analysis to cells that do not carry a cell value of no data?

analysis mask

what manipulates raster layers using math-like expressions?

map algebra

what are the four types of map algebra operations?

• local operation

• Neighborhood operations

• Zonal Operation

• Global operations

local operations are also called?

cell-by-cell operations

local operation that creates a new raster by classification

reclassification

neighborhood operations involve?

a focal cell and a set of surrounding cells

zonal operations work with?

two raster data layers

one of the zonal operation layers is?

the defining zone layer

global operations create rasters where

each cell is a function of the entire grid

Euclidean distance tools measure

straight-line distance

two common types of terrain data are

• raster based DEM

• Vector Based TIN

errors in DEM are classified as

• global error

• Relative error

relative errors are fixed by

filling peaks and sinks in DEM data

slope identifies

max rate of change from each cell to its neighbors

output slope rasters can be calculated as

percent slope or degree of slope

when finding cell slopes how do you find the distance to a diagonal placed cell?

(d^2+d&2)^(1/2)

ArcGIS uses ____ to find slope

horn's algorithm

what factors influence slope and aspect measurement?

• resolution

• quality

• Computing algorithm

• Local topography

aspect is the?

directional measure of slope

how is aspect determined?

it starts at 0 degrees at North and moves clockwise

contour lines are

lines connecting points of equal elevation

contour interval is

vertical distance between contour lines

base contour is

contour from which contouring lines start

contour lines cannot

intersect

a viewshed analysis is

the portion of land visible from one or more viewpoints

viewshed analysis is based on

line of sight

a watershed is

the area of land that drains to one stream

watershed analysis refers to

using DEMs and raster data to delineate watersheds and derive stream networks

delineation can be based on

• area based

• Point based

a sink is

area surrounded by higher elevation values

it is _____ to find 1% of the cells in a 30 meter resolution DEM to be sinks

not uncommon

flow directions show

the directions water will flow out of cells in a filled elevation raster

flow direction is determined by

elevation of surrounding cells

in a flow direction how many cells can water flow into

only one

flow accumulation rasters show

the number of cells that will flow into it

in the strahler method, stream order increases when

streams of the same order intersect

which method is the most common stream ordering method

strahler

in the shreve method, stream order

adds when two streams intersect

points of interest in point-based watersheds are called

pour points or outlets

descriptive analysis describes

the location of data and how much the data varies

measures of location include

-mean

-median

-mode

the 1st law of geography is

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

spatial autocorrelation is

the correlation of a variable with itself through space

measure of spatial autocorrelation describe

degree to which observations at spatial locations are similar

when nearby areas are more alike this is

positive spatial autocorrelation

when nearby areas are unlike this is

negative autocorrelation

random patterns exhibit

no spatial autocorrelations

Moran's I is used to indicate

spatial autocorrelation

Moran's I compares

the value at any one location to the value at all other locations

Moran's I > 0 indicates

positive autocorrelation

Moran's I = 0 indicates

random spatial pattern

G values calculate

clustering of high and low values in a data set

+Z values and significant p values indicate

clustering of high values

-Z values and significant p values indicate

clustering of low values

a local Moran's I is called

LISA

LISA compute _____ and _____ for every point

z score and p value

high I score indicates

feature is adjacent to features of a similar value

hotspot analysis is a

local G statistic

hotspot analysis computes

a z score for every feature

a cluster of high positive z values indicates

a cluster of high values or a hotspot

spatial interpolation is the process of

using points with known values to estimate values at other points

types of interpolations

• global, uses every point

• local, uses a sample data

• exact, predicts a value the same as known value

• inexact, predicts a value different the known value

• deterministic, does not include possible error

• stochastic, explains prediction of error

thiessen polygons or voronoi polygons assume

any point within polygon is closer to the polygon's known point than other known points

in IDW all estimated values

are between max and min known points

spline is a ____ interpolation method

exact

spine types

-regularized type

-tension type

spine values are not

limited to the min and max known points

the problem with spline is that

it can create steep gradients in data poor areas

line density calculates

magnitude per unit area from polyline features

point density calculates

what are the two methods of density estimation

-simple

-kernel

kriging interpolation includes

autocorrelation, the statistical relationship among measured points

kriging uses the concept of

lag distance

semi-variance is a measure of

the degree of spatial dependence between observations

a semivariogram plots

average semi-variance against the average distance

nugget is the

initial semi-variance where autocorrrelation is typically the highest

sill is the

point where variogram levels of, background noise

range is the

lag distance at which sill is reached

anisotropy is

the existence of directional differences in spatial dependence

stationary in kriging

local variation doesn't change in different areas of the map

ordinary kriging

-assumes there is no drift or trend

-uses fitted semi variogram

universal kriging

-assumes there is drift/trend between sample points

-typically uses 1st or 2nd order polynomial

the trend tool uses

a global polynomial interpolation that fits a smooth surface

first order polynomial

no bend

second order polynomial

one bend

third order polynomial

two bends

regression models relate

a dependent variable to a number of independent variables

binary models are

true or false

index models calculate

index value for each unit area

model builders are used

for simple programming where a series of simple operations are chained together

reasons to use modelbuilder

• provide visual representation of data

• can be reused and shared

• easy to modify

• more convenient than running tools individually

arcpy tells python

that you're going to work with some special scripting functions

pure networks are

only topology and connectivity

a flow network is characterized by

its topology and flow characteristics

types of network analyses

-direct path, finding shortest path

-optimum routing

-closest facility

a link refers to

a road segment defined by two end points

link impedance is the

cost of traversing a link

turn impedance is the

time to complete a turn