PowerPointPrsentation

1
ISESS 2005Tools and Techniques
Guidelines for good practises in GIS
Andrea Schukraft, Roman Lenz
2
- Outline-
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)
Andrea Schukraft, Roman Lenz
Page 2
3
GIS data quality a problem in planning
processes?
- Example 1 -
The research project WAVES (TUM) in Brasil
Beispiel mit freundlicher Genehmigung von
Planungsbüro Voerkelius, Landshut
Andrea Schukraft, Roman Lenz
Page 3
4
GIS data quality a problem in planning
processes?
- Example 2 -
Landscape plan on a municipality level
Are the wet soils and potential habitats mapped
correctly? The farmer said no! (Scale...)
Beispiel mit freundlicher Genehmigung von
Planungsbüro Voerkelius, Landshut
Andrea Schukraft, Roman Lenz
Page 4
5
GIS data quality a problem in planning
processes?
- Example 3 -
Data capture (digitising) from analogous basic
data
Different location errors of a waste water
tube... again the context matters! (absolute vs.
relative position)
Beispiel mit freundlicher Genehmigung von
Planungsbüro Voerkelius, Landshut
Andrea Schukraft, Roman Lenz
Page 5
6
GIS data quality a problem in planning
processes?
- Example 4 -
Quality of the geometries
Multiparts
Andrea Schukraft, Roman Lenz
Page 6
7
What really is GIS data quality?
- Reality and maps -

• The map as
• representation of the earth
• as map sheet
• representing only partial aspects
• as a flash light representation

• The earth
• as globe
• with people, land use, ...
• in a permanent change

Andrea Schukraft, Roman Lenz
Page 7
8
What really is GIS data quality?
- Reality and maps -
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!!!
Andrea Schukraft, Roman Lenz
Page 8
9
What really is GIS data quality?
- Reasons for deviations/differences from reality
-
Andrea Schukraft, Roman Lenz
Page 9
10
What really is GIS data quality?
- Categories of Spatial data quality -
Precision (or resolution)
Accuracy (and actuality)
degree of detail that can be displayed in
space, time or theme
discrepancy between the encoded and actual
value of a particular attribute
Quality in Spatial Data
Consistency
Completeness
the absence of apparent contradictions in a
database
lack of errors of omissions in a database
Andrea Schukraft, Roman Lenz
Page 10
11
What really is GIS data quality?
- A classification matrix of data quality -
Andrea Schukraft, Roman Lenz
Page 11
12
What really is GIS data quality?
- Meta-data -
Meta-data are data about data

• For example
• Description of Geo-data
• Information about data quality
• Information about data format (shape, tif,
  raster, ...)
• Information about the spatial reference system
  (e. g. Gauß-Krüger)
• Additional information (e. g. description of
  table contents)
• Availability and sources (public or restricted,
  price, ...)
• Contact address

Andrea Schukraft EDV Im Grünen Bereich -
a.schukraft_at_edvimgruenenbereich.de
Seite 12
13
What really is GIS data quality?
- Meta-data -
Title
Source of data
Map-Scale
Date of publication
Key words
Purpose of data capture
Actualitye.g mapping date
Short summary
Andrea Schukraft, Roman Lenz
Page 13
14
What really is GIS data quality?
- Meta-data -
Why do we need Meta-data?

• 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

Andrea Schukraft, Roman Lenz
Page 14
15
Steps for improvements
How do we solve the problems in practise/reality?
Andrea Schukraft, Roman Lenz
Page 15
16
Quick check of spatial precision
- Derive precision from origin -
Precision of the resulting data set
Original data
Analysis
17
Sample Implementation
- Visualize precision -
18
Steps for improvements
- Example 4 -
Quality of the geometries
Andrea Schukraft, Roman Lenz
Page 18
19
Steps for improvements
- Example 5 -
Modelling flooding
Andrea Schukraft, Roman Lenz
Page 19
20
Guidelines for good practices in GIS
Handbook on GIS data quality (management)
Andrea Schukraft, Roman Lenz
Page 20
21
Guidelines for good practices in GIS

• Handbook -

Andrea Schukraft, Roman Lenz
Page 21
22
Guidelines for good practices in GIS

• Contents -

Andrea Schukraft, Roman Lenz
Page 22
23
- Example 1 -
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

Andrea Schukraft, Roman Lenz
Page 23
24
- Example 1 -
Example 1 Quality of geometries
Is it really necessary, to define and demand such
trivial criteria?
Yes !!!
Andrea Schukraft, Roman Lenz
Page 24
25
- Example 2 -
Example 2 Meta-data
How did these results occur?
Andrea Schukraft, Roman Lenz
Page 25
26
- Example 2 -
Example 2 Meta-data
Andrea Schukraft, Roman Lenz
Page 26
27
- Example 3 -
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 little
• points will be digitised, and
• hence the data set will not
• be precise enough

Andrea Schukraft, Roman Lenz
Page 27
28
- Example 3 -
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

Andrea Schukraft, Roman Lenz
Page 28
29
ISESS 2005Tools and Techniques
Guidelines for good practises in
GIS www.rundertischgis.de
Thanks for listening!
Andrea Schukraft, Roman Lenz