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GIS > GIS midter, > Flashcards

GIS midter, Flashcards

1
Q

What is representation?

A

The real world is infinitely complex
Communication requires simplification
Reduce information to a manageable volume

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2
Q

Why representation?

A

To communicate
To go beyond the space-time limits of our senses
To deal with an infinitely complex world

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3
Q

Digit (meaning finger)

A

Computers represent information using some combinations of 0s and 1s

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4
Q

One binary digit is a

A

bit

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5
Q

eight bits is a

A

byte

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6
Q

“digital” =

A

binary

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7
Q

16-bit short integer

A

Storage bit in bytes – 2

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8
Q

32-bit long integer

A

Storage bit in bytes – 4 or 8

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9
Q

Single precision floating-point numbers

A

32 bits in total
1 sign bit, 8 exponent bits, 24 fraction bits (23 explicitly stored)
7 significant digits in decimal system

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10
Q

Model process

A

Reality => Conceptual model => Logical model => Physical model

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11
Q

Reality

A

Includes all aspects and may or may not be perceived by individuals

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12
Q

Conceptual model

A

Identify the main (relevant) object types and their relationships

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13
Q

Logical model

A

Create diagrams and lists describing the object types and Independent from implementation

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14
Q

Physical model/data model

A

Actual files or database tables for data storage in computer systems andSystem-specific formats

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15
Q

CAD - Computer-Aided Design

A

Geometric models for objects (2D and 3D vector
Local drawing coordinates
Individual objects do NOT have unique identifiers for linking with attributes

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16
Q

What does CAD lack

A

relationships (e.g., topology) between objects

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17
Q

Graphical model

A

Digitizing paper maps
Points, lines, polygons, and annotations with geographic coordinates

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18
Q

What does graphical model not have

A

linkages with attributes
relationships between objects

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19
Q

Raster

A

An array of cells/pixels
Geographically referenced
Every cell holds only a value

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20
Q

VAT (Value Attribute Table)– multiple attributes

A

Were saved as a table linked to raster
Are not built or available for floating point raster
May exist for integer grids

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21
Q

What is VAT (Value Attribute Table) in

A

Raster

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22
Q

Geo-tagging (not GIS raster model!)

A

Pictures/photographs
Linked to geographic objects as attributes in database
Stored in BLOB as object attributes in databases

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23
Q

Vector

A

Geographic locations are explicit
A point is associated with a single set of coordinates (X, Y)

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24
Q

Topological

A

Improve data validation (Assure Connectivity, remove loose ends, Remove gaps, & Close polygons)
Assist data editing (Shared boundaries, Snapping, & Auto-closure)

25
Q

What is topological in

A

Vector

26
Q

Advantages of Raster

A

Simple data structure
Simple for processing/programming
Easy and efficient overlaying
High spatial variability is efficiently represented

27
Q

Advantages of Vector

A

Compact data structure
Efficient for network analysis
Efficient projection transformation
Accurate representation of locations

28
Q

Disadvantages of Raster

A

Inefficient use of computer storage
Less accurate representation of locations
Errors in perimeter, area, and shape
Difficult network analysis
Inefficient projection transformations
Loss of information when using large cells

29
Q

Disadvantages of Vector

A

Complex data structure
Difficult overlay operations
High spatial variability is inefficiently represented
Not compatible with RS imagery

30
Q

TIN - Triangulated Irregular Networks

A

Topological vector
More accurate and use less space than grids
Can describe more complex surfaces than grids, including vertical drops and irregular boundaries

31
Q

Issue of TIN - Triangulated Irregular Networks

A

Not compatible with many geoprocessing tools
Subject to extreme values from raw data

32
Q

Object-Oriented Programming (OOP)

A

a program is a collection of cooperating objects that are self-contained and able to communicate with each other by sending/receiving messages

33
Q

Cardinality

A

Constraint on the number of objects that can be associated with other objects

34
Q

DBMS

A

a specialist software application that controls the creation, maintenance, and use of databases

35
Q

What does DBMS

A

Reducing redundancy (single location storage)
Reduced maintenance costs
Enabling data sharing – multi-users & concurrent access
Enforcing security – access rights
Suited for large-volume datasets

36
Q

(SQL) Standard/Structured Query Language

A

A specialist language designed for managing tabular data in RDBMS
Supported by virtually all mainstream databases

37
Q

Subclass

A

A subset of features in a feature class or objects in a table that share the same attributes

38
Q

What are you able to do with Subclass

A

Allow you to further diversify objects without creating too many new feature classes (inheritance)
Preserve the integrity of your data

39
Q

Split policy

A

Owner duplicated
Default values
Geomatic ratio of the split feature

40
Q

Merge policy

A

Default value
Sum values being merged
Weighted average of the two

41
Q

Relationship classes

A

Based on the common field with same data type
Used to maintain referential integrity of objects

42
Q

A primary key is a

A

column that uniquely identify a row

43
Q

A foreign key is a

A

column or set of columns in one table whose values must have matching values in the primary key of another table

44
Q

Spatial Relationship

A

Between two geometries (base and comparison), each includes one or more geographic objects
Returns Boolean value, no new geometry created!

45
Q

Topological operation

A

Operators that return geometry based on spatial relationships

46
Q

Indexing

A

Special representation of object information that improves searching
Allows random instead of sequential access
Improve searching performance, especially for large databases

47
Q

R-Tree indexing

A

Based on minimum bounding rectangles (MBR)
An object is added to the MBR that would expand the least
Large MBR will be split

48
Q

Versioning

A

Enterprise geographic databases allow multi-user concurrent access (read/write)
Creating logical copies of the parent tables for each user (with write right) for editing/updating

49
Q

Network structure

A

Topological vector: nodes and arcs
Flow: directions and capacity
Linear referencing: dynamic segmentation ESRI geodatabase: geometric and logical; connectivity rules, and flow

50
Q

Basics of geometric transformation

A

the process of changing the geometry of a raster dataset from one coordinate space to another

51
Q

Higher order transformation

A

More complicated
More distortion can be corrected
Rarely higher than third order

52
Q

Affine Transformation

A

first order

53
Q

Basic of Geodatabase Managed – stored “within” the database

A

Raster datasets always stored as managed
Mosaic datasets as unmanaged
All ArcSDE geodatabase rasters stored as managed

54
Q

Basic of Geodatabase Unmanaged – pointers to existing raster files

A

Raster catalogs and rasters as attributes can use both managed and unmanaged sources

55
Q

TIN - Triangulated Irregular Network

A

Vertices (nodes) of triangular faces have [X, Y, Z] coordinates
Efficient and accurate surface model
Representing surfaces as contiguous nonoverlapping triangular faces

56
Q

Storage of TIN (Triangulated Irregular Network

A

A table of nodes (coordinates) and a table of triangles (topology)
2D topology for 3D space (2.5D)

Delaunay Triangulation

Create triangles that collectively are as close to equilateral shapes as possible

57
Q

TIN can NOT be stored in an ESRI instead

A

Direct file

58
Q

Delaunay Triangulation

A

Create triangles that collectively are as close to equilateral shapes as possible

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