Data structure Mapping data What data you need to entry Exact - - PDF document

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data structure mapping data what data you need to entry
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Data structure Mapping data What data you need to entry Exact - - PDF document

Mar 05, 2023 216 likes •675 views

Attributes and features Data structure Mapping data What data you need to entry Exact location (case specific) Aggregated data by administrative levels (aggregated) Aggregated data are usually represented by polygons A field for the

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SLIDE 1

Data structure

Attributes and features

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SLIDE 2

Mapping data

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SLIDE 3

What data you need to entry

  • Exact location (case specific)
  • Aggregated data by administrative levels

(aggregated)

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SLIDE 4

A field for the definition

  • f the attribute.

In other types of files this field is filled with the XY coord of each corner

  • f the polygon

Aggregated data are usually represented by polygons

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SLIDE 5

A row: a specific geographical area A column: a variable or field

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SLIDE 6

Exact point representation

Each point is represented by Specific XY coordinates

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SLIDE 7

Databases have to be relational

  • You can produce your data from any database
  • To be respresented geographically this table

needs a field in common to the tables of the map database (name, ID, etc)

  • In this way the tables can be related (joined) in
  • ne single table
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SLIDE 8

Data collected Table for geographic representation Geographic representation

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SLIDE 9

Relational database aggregated data

datanorm.rec

Levcode (unique) What When Age group Count Levcode What Rate

Disease.rec

Levcode (unique) Municipality (lowest level) Province Region

  • Geographic. dbf

Levcode Municipality Population

Level.rec

.dbf

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SLIDE 10

Data related and represented

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SLIDE 11

Spatially join point and polygon layers

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SLIDE 12

Spatially join point and polygon layers

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SLIDE 13

Spatially join point and polygon layers

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SLIDE 14

Spatially join point and polygon layers

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SLIDE 15

Respresenting specific location

  • You need to produce a new layer to be
  • verposed on the map
  • To do that the layers need to be in the same

geographical projection

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Layer with same projections

  • WGS84…….this is the key-ward!!!!!!

World Geodetic System

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Two layers

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SLIDE 18

Two layers

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SLIDE 19

Two different tables One for each layer

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SLIDE 20

Distribution of IDPs camps in Darfur, Sudan, 2004

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SLIDE 21

Managing administrative boundaries

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SLIDE 22

Managing administrative boundaries

  • Structure of database
  • Starting from the lowest administrative

representation

  • Ensure that the database structure remains the

same

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SLIDE 23
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SLIDE 24

Province District

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Geoprocessing operation to easily manage administrative boudaries

  • Dissolving features (loose boundaries)
  • Merging features (preserve your boundaries)
  • Clipping one feature on another (cutting)
  • Intersecting two features (overlay)
  • Creating new administrative areas
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SLIDE 26

Dissolving to create upper administrative levels

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SLIDE 27

Possible representation of the real world

Campus.esri.com 2000

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SLIDE 28

GIS, characteristics

  • Format Vectorial
  • Format Raster
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SLIDE 29

Vector format

Points Lines Polygons Data are localized by coordinates

x,y That represent a specific position on the Earth

.

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SLIDE 30

Connectivity Contiguity

Vector format

Adapted From ESRI, Virtual Campus

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SLIDE 31

Vector Format

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SLIDE 32
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SLIDE 36
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SLIDE 37

Limits of vector format

  • Area in polygons is assumed to be uniform

e.g.(population distribution)

  • Objects represented depends very much from

scale representation (the choice of the scale is determined by the initial resolution of epi data)

  • Adyacency between objects (common boundary
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SLIDE 38

Reccomandation for vector format

  • Properly mantained database, the minimal

mapping unit is indicated

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SLIDE 39

Raster format

The raster format are represented by grids x y Satellite images

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SLIDE 40

Raster format

Cells and their localization

Campus.esri.com 2000

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SLIDE 41

Raster format

Comparison between vector and raster format

Campus.esri.com 2000

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SLIDE 42

Raster format

Position and value of cells

Campus.esri.com 2000

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SLIDE 43

Data quality

  • Additional sources of errors in spatial analysis:

– Spatial – Resolution – Interpretative – Temporal

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SLIDE 44

Data quality

  • Spatial errors:

– Displacement (data entry, methods to locate

  • Resolution errors:

– Definition of minimal mapping unit

  • Intepretative error:

– Where the « case » is placed

  • (residence, exposure, onset, notification)
  • Temporal error:

– When (time between exposure and onset)