Vector Data Structures and Vector-Raster Conversion in GIS, Study notes of Geography

An overview of vector data structures, their advantages and disadvantages, and the process of converting vector data to raster and vice versa in geographic information systems (gis). Vector data structures are used to represent linear features and facilitate topologically-based analyses, while raster models are suitable for continuous data and certain types of analysis. Topics such as precision and accuracy, encoding vector data, constructing a vector database, and the complexities of editing and overlaying vector data.

Typology: Study notes

Pre 2010

Uploaded on 09/17/2009

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Vector Data Structure
Fundamental unit is the x, y coordinate (vertex)
points are explicitly defined
lines, arcs and polygons are constructed
Map area is presumed continuous
position can be defined with great precision;
limited by precision of software/hardware and
source data
Usually provides finer spatial resolution than
raster model
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Vector Data Structure

•^

Fundamental unit is the x, y coordinate (

vertex

– points are explicitly defined– lines, arcs and polygons are constructed

•^

Map area is presumed continuous– position can be defined with great precision;

limited by precision of software/hardware andsource data

•^

Usually provides finer spatial resolution thanraster model

Precision vs. Accuracy

•^

Precision

- the degree of specificity to which a

measurement is described (e.g., number ofdecimal places)

•^

Accuracy

- the closeness of results, computations

or estimates to true values (or values accepted tobe true)– true location, size or condition

Encodinga Map inVectorFormat

Point Features

Area Features

Constructing a Vector Database

“Build”

Relational Database Management

System (RDBMS)

Key

– a common field that allows tables

to be linked (“joined”)

Distributed Databases

Representing Surfaces

(e.g., elevation, pressure, temperature)

Representing Surfaces

Triangulated Irregular Network (TIN)

• TIN wasgeneratedfrom 6% ofdata pointsfrom rasterDEM• TIN usesonly the mostcritical pointsneeded tocapture thesurfaceconfiguration

TIN Data Structure

Data in Vector Format

Soils

Digital Line Graph- roads

Digital Line Graph- hydrography

Vector Overlay is Complex

2 polygons 3 polygons 6 newpolygons B 2 A

3

1

B B1 A

A A

B

  • New polygons• New attributes• New topology