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GIS midter, Flashcards

(58 cards)

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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

Study These Flashcards
A

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

25
What is topological in
Vector
26
Advantages of Raster
Simple data structure Simple for processing/programming Easy and efficient overlaying High spatial variability is efficiently represented
27
Advantages of Vector
Compact data structure Efficient for network analysis Efficient projection transformation Accurate representation of locations
28
Disadvantages of Raster
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
Disadvantages of Vector
Complex data structure Difficult overlay operations High spatial variability is inefficiently represented Not compatible with RS imagery
30
TIN - Triangulated Irregular Networks
Topological vector More accurate and use less space than grids Can describe more complex surfaces than grids, including vertical drops and irregular boundaries
31
Issue of TIN - Triangulated Irregular Networks
Not compatible with many geoprocessing tools Subject to extreme values from raw data
32
Object-Oriented Programming (OOP)
a program is a collection of cooperating objects that are self-contained and able to communicate with each other by sending/receiving messages
33
Cardinality
Constraint on the number of objects that can be associated with other objects
34
DBMS
a specialist software application that controls the creation, maintenance, and use of databases
35
What does DBMS
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
(SQL) Standard/Structured Query Language
A specialist language designed for managing tabular data in RDBMS Supported by virtually all mainstream databases
37
Subclass
A subset of features in a feature class or objects in a table that share the same attributes
38
What are you able to do with Subclass
Allow you to further diversify objects without creating too many new feature classes (inheritance) Preserve the integrity of your data
39
Split policy
Owner duplicated Default values Geomatic ratio of the split feature
40
Merge policy
Default value Sum values being merged Weighted average of the two
41
Relationship classes
Based on the common field with same data type Used to maintain referential integrity of objects
42
A primary key is a
column that uniquely identify a row
43
A foreign key is a
column or set of columns in one table whose values must have matching values in the primary key of another table
44
Spatial Relationship
Between two geometries (base and comparison), each includes one or more geographic objects Returns Boolean value, no new geometry created!
45
Topological operation
Operators that return geometry based on spatial relationships
46
Indexing
Special representation of object information that improves searching Allows random instead of sequential access Improve searching performance, especially for large databases
47
R-Tree indexing
Based on minimum bounding rectangles (MBR) An object is added to the MBR that would expand the least Large MBR will be split
48
Versioning
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
Network structure
Topological vector: nodes and arcs Flow: directions and capacity Linear referencing: dynamic segmentation ESRI geodatabase: geometric and logical; connectivity rules, and flow
50
Basics of geometric transformation
the process of changing the geometry of a raster dataset from one coordinate space to another
51
Higher order transformation
More complicated More distortion can be corrected Rarely higher than third order
52
Affine Transformation
first order
53
Basic of Geodatabase Managed – stored “within” the database
Raster datasets always stored as managed Mosaic datasets as unmanaged All ArcSDE geodatabase rasters stored as managed
54
Basic of Geodatabase Unmanaged – pointers to existing raster files
Raster catalogs and rasters as attributes can use both managed and unmanaged sources
55
TIN - Triangulated Irregular Network
Vertices (nodes) of triangular faces have [X, Y, Z] coordinates Efficient and accurate surface model Representing surfaces as contiguous nonoverlapping triangular faces
56
Storage of TIN (Triangulated Irregular Network
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
TIN can NOT be stored in an ESRI instead
Direct file
58
Delaunay Triangulation
Create triangles that collectively are as close to equilateral shapes as possible

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