ISESS 2005ISESS 2005Tools and TechniquesTools and Techniques
Guidelines for good practises in GISGuidelines for good practises in GIS
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz
Part 1: GIS data quality – a problem in planning processes?
Part 2: What really is GIS data quality?
Part 3: Steps for improvements
Part 4: The handbook for GIS data quality (management)
- Outline-- Outline-
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 22
GIS data quality – a problem in planning
processes? - Example 1 -- Example 1 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 33
The research project WAVES (TUM) in Brasil
Beispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, LandshutBeispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, Landshut
GIS data quality – a problem in planning
processes? - Example 2 -- Example 2 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 44
Landscape plan on a municipality level
Beispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, LandshutBeispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, Landshut
Are the wet soilsand potential habitatsmapped correctly?The farmer said: no!(Scale...)
GIS data quality – a problem in planning
processes? - Example 3 -- Example 3 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 55
Data capture (digitising) from analogous basic data
Beispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, LandshutBeispiel mit freundlicher Genehmigung von Planungsbüro Voerkelius, Landshut
Different locationerrors of a wastewater tube...again the contextmatters!(absolute vs. relativeposition)
GIS data quality – a problem in planning
processes? - Example 4 -- Example 4 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 66
Quality of the geometries
Multiparts
What really is GIS data quality?What really is GIS data quality?
- Reality and maps -- Reality and maps -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 77
The earth
as globe with people, land use, ... in a permanent change
The map as
representation of the earth
as map sheet representing only partial aspects as a flash light representation
What really is GIS data quality?What really is GIS data quality?
- Reality and maps -- Reality and maps -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 88
Quality is (after DIN) defined as
„the completeness of attributes of a specific unit (product, service) according to its suitability, to fullfill fixed and presupposed needs"
(DIN ISO 8402, 1992). There are no bad or good data!
There are only data, which are suitable for a specific
purpose!!!
What really is GIS data quality?What really is GIS data quality?
- Reasons for deviations/differences from reality -- Reasons for deviations/differences from reality -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 99
Soft transitions or fuzzy borders in nature distinct lines in maps
cartographic treatment
age of data
method of data capture
conversion into a more suitable data format
...
What really is GIS data quality?What really is GIS data quality?
- Categories of Spatial data quality -- Categories of Spatial data quality -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1010
Completeness
Quality in Spatial Data
= lack of errors of omissions in a database
Consistency
= the absence of apparent contradictions in a database
Accuracy (and actuality)
= discrepancy between the encoded and actual value of a particular attribute
Precision (or resolution)
= degree of detail that can be displayed in space, time or theme
What really is GIS data quality?What really is GIS data quality?
- A classification matrix of data quality -- A classification matrix of data quality -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1111
Space - where?
Time - when?
Theme - what?
Accuracy 1 2 3
Precision 4 5 6
Complet-ness
7 8 9
Consistency 10 11 12
What really is GIS data quality?What really is GIS data quality?
- Meta-data -- Meta-data -
Andrea Schukraft – EDV Im Grünen Bereich - [email protected] Schukraft – EDV Im Grünen Bereich - [email protected] Seite Seite 1212
Meta-data are data about data
For example:
1. Description of Geo-data
2. Information about data quality
3. Information about data format (shape, tif, raster, ...)
4. Information about the spatial reference system (e. g. Gauß-Krüger)
5. Additional information (e. g. description of table contents)
6. Availability and sources (public or restricted, price, ...)
7. Contact address
What really is GIS data quality?What really is GIS data quality?
- Meta-data -- Meta-data -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1313
Minimum-InfoMinimum-Info
Source of data
Title
Date of publication
Purpose of data capture
Actualitye.g mapping date
Key words
Map-Scale
Short summary
What really is GIS data quality?What really is GIS data quality?
- Meta-data -- Meta-data -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1414
- Geo-data investigations
- Description of own data, e.g. in the office etc.
- Re-use of data e.g. after a longer period
- After transmission of data, meta-data are an important information for the receiver
- Institutions, who distribute/sell data, describe those in a catalog. The descriptions are meta-data
- Notice: “science” or “theoretical” standards (like FGDC or ISO 19115) vs. reality…
Why do we need Meta-data?
Steps for improvements
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1515
How do we solve the problems in practise/reality?
Quick check of spatial precisionQuick check of spatial precision
- Derive precision from origin -- Derive precision from origin -
Precision ofthe resulting
data set
Original data Analysis
Sample ImplementationSample Implementation
- Visualize precision -- Visualize precision -
Steps for improvements
- Example 4 -- Example 4 -
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Quality of the geometries
Steps for improvements
- Example 5 -- Example 5 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 1919
Modelling flooding
Guidelines for good practices in GISGuidelines for good practices in GIS
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2020
Handbook on GIS data quality (management)
Guidelines for good practices in GISGuidelines for good practices in GIS
- Handbook -Handbook -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2121
Guidelines for good practices in GISGuidelines for good practices in GIS
- Contents -Contents -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2222
- Example 1 -- Example 1 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2323
Example 1: Quality of geometries
Quality criteria for geometries will be fixed, e.g.
- for comparison of competing offers e.g. in public calls
- for own data captures
- for data transfer between several project partners
- Example 1 -- Example 1 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2424
Example 1: Quality of geometries
Is it really necessary, to define and demand such
trivial criteria?
Yes !!!
- Example 2 -- Example 2 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2525
Example 2: Meta-data
How did these results
occur?
- Example 2 -- Example 2 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2626
Example 2: Meta-data
- Example 3 -- Example 3 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2727
Example 3: Pre-definition of digitising map-scale
Why are pre-definitions necessary?- in a large scale, too many points will be digitised, and the data set gets too big- in a small scale, too littlepoints will be digitised, andhence the data set will notbe precise enough
- Example 3 -- Example 3 -
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz Page Page 2828
Example 3: Digitising Map-scale
When is it meaningful to pre-define
the map-scale for digitising?
- if different people are digitising
- if data are captured over a longer period
- if a third party is capturing and digitising the data
ISESS 2005ISESS 2005Tools and TechniquesTools and Techniques
Guidelines for good Guidelines for good practises in GIS:practises in GIS:
www.rundertischgis.dewww.rundertischgis.de
Andrea Schukraft, Roman LenzAndrea Schukraft, Roman Lenz
Thanks for listening!