Module 9

Question 1

Define spatial analysis and provide two examples we have talked about in the past

Answer 1

▪ spatial analysis refers to a set of methods used to examine, summarize, manipulate,
and predict spatial patterns, spatial relationships, trends, and their underlying
causes
▪ spatial analysis provides a means
of turning spatial data into useful
information and knowledge, and
is the central component for
environmental problem solving
and decision making
▪ the product of spatial analysis is
composed of new datasets, and
maps and tables demonstrating
the results of the applied analysis

we’ve already seen some of these methods:
▪ attribute and location queries are relatively simple approaches to identifying
where certain phenomena exist or where one phenomena exists in relation to
another
▪ network analysis uses specifically designed network datasets to assess spatial
relationships and use least-cost approaches for answering various research
questions

Question 2

there are 2 ways to select features in GIS

Answer 2

– interactive selection or query selection

Question 3

Rules of SQL Queries(5)

Answer 3

▪ rules for evaluation:
1. expression always evaluated left to right
2. expressions within parentheses assume highest
priority
3. if parentheses are nested, the evaluation starts
with the innermost parentheses
4. AND is evaluated before OR
5. NOT is evaluated before AND and OR

Question 4

Reclassification for vector and raster

Answer 4

▪ reclassification is used to recode the attributes of features in the attribute table or
reclassify the grid values to produce a new raster layer

Vector:
▪ with vector data, the field calculator is used to reclassify a field in the attribute table
▪ assign new values to classes or ranges of the existing
values to reduce the number of classes or ranges in the
original input layer
▪ group attribute values into categories in a new
classification scheme
-the primary goal of vector reclassification is to take many different feature types and group them into a lesser number of feature types

Raster:
raster reclassification is commonly used for DEMs, where the high resolution continuous surface is reclassed into discrete elevation bands, or to produce binary maps (presence / absence)
▪ assign ranks, orders, ratings, or weights representing preference, importance,
priority, sensitivity, suitability, capability, or other criteria to unique values,
ranges, or categories of values in the input layer
▪ eg, use reclass to assign new values to different land use classes based on
their ecological importance to help identify areas of high conservation value
▪ eg, use reclass to assign values 1 – 10 to different ranges of slope to represent
landslide risk

Question 5

Vector Reclassification is a..

Answer 5

this is why it is a data

simplification technique

Question 6

For a _______ coordinate system the shortest distance between two points is a straight line versus a _____ coordinate system which is a curved line(great circle)

Answer 6

projected

geographic

Question 7

Raster area is calculated by

Answer 7

area is calculated as the cell resolution multiplied

by the number of cells in the polygon

Question 8

3 CATEGOIRES OF SHAPE MEASURES

Answer 8

1. Compactness:quantifies how far a feature deviates from a standard shape (a circle or square), which is considered to be the most compact

2.Boundary:quantitatively describe the roughness or the smoothness of a feature’s outer edge (a smoother boundary has fewer edges), and is an
indicator of shape complexity

3.Form: quantify the overall geometric configuration of a feature by comparing it to a standard shape such as a circle

Question 9

for standard
shapes SIc(compactness) = \_\_ and the further below that number...

Answer 9

1

means its less compact
-anything <1

Question 10

for standard smoothness of the boundary is __ and as it gets rougher it is closer to __

Answer 10

1

2

Question 11

buffering

Answer 11

▪ buffering is a common vector data distance measurement tool that creates a zone
around a feature or a set of features with a specific width – the zone is called a
buffer

Question 12

Using dissolve when buffering mean..

Answer 12

that the objects, if they have overlapping buffers, will connect instead of each having individual overlaps

Question 13

▪ in a projected coordinate system, the buffer distance
is measured in _______ as a ______ buffer

▪ in a geographic coordinate system, the buffer size is
determined by _____ distance measurement

Answer 13

cartesian space, Euclidean

geodesic

Question 14

ringed buffers

Answer 14

.ringed buffers are common to use when the influence diminishes with distance from the feature

Question 15

vector uses buffers while rasters use..

Answer 15

distance surfaces

Question 16

distance surfaces

Answer 16

▪ distance measurement in raster calculates the shortest distance from the
location(s) representing the source(s)/origin(s) to every other location and creates
a distance surface in raster

▪ distance in raster may be measured based on
absolute physical distance between places, or costs
incurred while traversing the physical distance,
known as a cost or weighted distance (eg, travel time,
energy consumption, etc)

Question 17

ARCGIS uses the _____ algorithm to generate the cost distance surface

Answer 17

spreading

Question 18

Least Cost path approach

Answer 18

▪ networks are typically analyzed using a least-cost path approach – this can be used
for rasters as well
▪ the output of this analysis is a cost distance
raster and direction raster, which records the
sequence of movements that created the cost
distance raster

Question 19

Overlay Analysis

Answer 19

▪ overlay analysis is the process of stacking multiple data layers registered to a
common georeferencing system on top of each other so that the relationships
between features at each location can be analyzed

vector:▪ for vector data, overlay analysis involves combining geometries and attributes
from the input vector layers into a single vector layer

raster:raster overlay can be used to perform
arithmetical, logical, relational, conditional,
and statistical operations on the input
rasters
-raster overlay analysis with mathematical operators is commonly referred to as
map algebra and is a common tool available in many GIS platforms

Question 20

▪_______ overlay determines which areas a line feature is crossing

Answer 20

line-in-polygon

Question 21

▪ ________ combines 2 polygon layers and calculates the geometric
intersection of the input features creating a new set of polygons with original
boundaries split at intersections

Answer 21

polygon-in-polygon

Question 22

6 types of overlay

Answer 22

1. Union:All features and their attributes will be written to the output feature class.
   - keeps all the features from the 2 input layers

2.Identity:keeps all the features in the 1st input
layer and deletes the portions of the 2nd input
layer that fall outside the boundary of the first

3.Intersect:preserves the features or portion of the
features that fall within the common area of all
inputs

4. Erase:Only those portions of the input features falling outside the erase features outside boundaries are copied to the output feature class.
5. Symetrical Difference:Features or portions of features in the input and update features that do not overlap will be written to the output feature class
6. Spatial Join

Question 23

the output feature type of vector
overlay will always be of the same type
or a type of the input features with the…

Answer 23

lowest dimension geometry (eg, if any
of the inputs are points, the output will
be point)

Question 24

map algebra

Answer 24

▪ map algebra is the application of raster data analysis and mathematical operators
and functions to an algebraic equation with raster data layers as input variables to
produce a new raster as a solution

Question 25

Raster Overlay analysis(6) | basic understanding of each

Answer 25

1. Arithmetic: + − × ÷ power square root exponential logarithm 2. Logical: AND OR NOT 3. Relational: = > ≥ < ≤ 4. Conditional: IF…THEN… IF…THEN…ELSE… 5. Trigonometric: sin cos tan sin−1 6.Statistical: maximum minimum mean range standard deviation sum median mode majority minority variety

Question 26

▪ map algebra expressions are built inside the ______

Answer 26

raster calculator

Question 27

▪ the most common method of map algebra uses ____ functions, performing cell-bycell analysis

Answer 27

local

Question 28

Raster Overlay Analysis 5 types

Answer 28

1. Those that work on single cell locations (local operations) 2. Those that work on cell locations within a neighborhood (focal operations) 3. Those that work on cell locations within zones (zonal operations) 4. Those that work on all cells within the raster (global operations) 5. Those that perform a specific application (for example, hydrologic analysis operations)

Question 29

kernels

Answer 29

▪ irregularly shaped neighbourhoods are known as kernels, and can be used to apply weights to specific cells in the neighbourhood

Question 30

zonal functions

Answer 30

zonal functions calculate a new value for every cell in the output raster as a function of the existing values of the cells belonging to the same zone ▪ a zone is a group of cells of the same value