GIS Analytical Methods

Question 1

Overlay Analysis

Answer 1

Define problem - break problem into submodels - Determine significant layers ( some of these layers may need to be created) - reclassify or transform data within a layer

Question 2

Spatial Overlay

Answer 2

process of superimposing layers of geographic data that cover the same are to study the relationship between them

Question 3

Overlay

Answer 3

two or more maps or layers are superimposed for showing relationships between features

Question 4

Identify ( Vector Overlay)

Answer 4

Input features, split by overlay features

Question 5

Intersect (vector Overlay)

Answer 5

Only features common to all input layers

Question 6

Symmetrical Difference ( Vector Overlay)

Answer 6

Features common to either input layer or overlay, layer but not both

Question 7

Union (Vector Overlay)

Answer 7

All input features

Question 8

Update ( Vector Overlay)

Answer 8

Input feature geometry replaced by update layer

Question 9

Zonal Statistics (Raster Overlay)

Answer 9

summarizes values in a raster layer by zones (categories) in another layer- for example, calculate the mean elevation for each category

Question 10

Combine (Raster Overlay)

Answer 10

assigns a value to each cell in the output layer based on unique combinations of values from several input layers

Question 11

Single Output Map Algebra (Raster Overlay)

Answer 11

lets you combine multiple raster layers using an expression you enter-for example you can add several ranked layers to create an overall ranking

Question 12

Weighted Overlay (Raster Overlay)

Answer 12

automates the raster overlay process and lets you assign weights to each layer before adding (you can also specify equal influence to create an unweighted display)

Question 13

Weighted Sum (Raster Overlay)

Answer 13

overlays several raster’s multiplying each by their given weight and summing them together

Question 14

Plane

Answer 14

flat, 2 dimensional surface

Question 15

Point

Answer 15

single coordinate pair

Question 16

Lines

Answer 16

ordered lists of coordinate pairs

Question 17

Polygons

Answer 17

ordered lists of coordinate pairs that reconnect

Question 18

Descriptive Statistics

Answer 18

discipline of quantitatively describing the main features of a collection of information - summarizes a sample to learn about the population

Question 19

Summary Statistics

Answer 19

used to summarize a set of observations

Question 20

Coefficient of Determination

Answer 20

R squared - number that indicates how well data fit a statistical model - fit to a line or curve - a 1 indicates the line fits perfectly with the data - 0 indicates the line does not fit at all ( data is random)

Question 21

Object oriented programming (OOP)

Answer 21

programming paradigm based on concept of “objects” which are data structures that contain data in the form of fields (aka attributes) and code in the form of procedures (aka methods) - most common are class based

Question 22

Extensibility

Answer 22

system design principle where the implementation takes future growth into consideration - level of effort to extend the system and implement the extension

Question 23

Vector

Answer 23

a coordinate based data model that represents features such as points, lines, polygons

Question 24

Raster

Answer 24

defines space as an array of equally sized cells arranged in rows and columns, single or multiple bands - each cell contains an attribute value

Question 25

Vector Advantages

Answer 25

represent point, line, area very accurately; more efficient than raster in storage; supports topology; interactive retrieval; enables map generalization

Question 26

Vector Disadvantages

Answer 26

less intuitively understood; multiple vectors overlay is computationally intensive; display and plotting vectors can be expensive

Question 27

Raster Advantages

Answer 27

easy to understand; good to represent surfaces; easy to input and output; easy to draw on a screen; analytical operations are easier

Question 28

Raster Disadvantages

Answer 28

inefficient for storage; compression techniques not efficient with variable data; large cells causes information loss; poor at representing points, lines, areas; each cell can be owned by only one feature; must include redundant or missing data

Question 29

Verbal Scale

Answer 29

expresses in words a relationship between a map distance and ground distance: one inch represents 16 miles

Question 30

Visual Scale

Answer 30

graphic scale or bar scale

Question 31

Representative scale

Answer 31

representative fraction or ratio scale 1:24,000 - 1” = 24,000”

Question 32

Absolute Scale

Answer 32

system of measurement that begins at a minimum or zero point and progresses in only one direction

Question 33

Relative Scale (arbitrary)

Answer 33

begins at some point selected by a person and can progress in both directions

Question 34

Display vs Data

Answer 34

The data is built at a certain scale/accuracy but once the data is displayed in any other format that the one it was made for, the scale gets warped. Ex. a map made as 9x10 that is then scaled down and printed in a newspaper

Question 35

1 mile =

Answer 35

5280ft/ 1.6093 km

Question 36

1 ft =

Answer 36

.3048m

Question 37

1 international nautical mile =

Answer 37

2025.4 yd / 6076.12 ft

Question 38

Radians

Answer 38

360 degrees is a whole circle. 2pi x radius is the circle

Question 39

Bearings

Answer 39

angle less than 90 degrees within a quadrant defined by the cardinal directions

Question 40

90 degrees

Answer 40

right angle; 194.60 minutes of arc in one degree; 195.60 seconds of arc in a minute

Question 41

Azimuth

Answer 41

angle between 0 degrees and 360 degrees measured clockwise from north