1. Technical Challenges of developing a common geographical dataset
Yvonne Gordon-Walker
WRc
Not a GIS problem – are reporting problems
When asked to do this, started with usual GIS issues of scale, completeness, accuracy etc, thinking about buffers etc.
The more I looked into it – the problem is not a GIS technical problem as such (although there are a number of technical issues that must be overcome) the main problems are related to reporting visualisation.

2. The Requirement
A European-wide dataset of drainage networks and catchment boundaries at suitable scale
to visualise the status of water bodies
to assess the change in status over time
Status of a water body may change over time. Water bodies themselves may also change over time so need a stable base against which the temporal changes can be visualised and assessed regardless of the scale at which the Member State defines and manages their water bodies.
Perception – every water body feature must be represented on the common dataset. Main purpose is to provide a graphical representation of the data at a scale suitable for comparison at an EU level. Main assessments etc likely to be done using tabular data.
Not all water bodies can be viewed at the scale so need to provide a geo-schematic view of the data which provides the hooks to the main data.

3. The Issue
Member States define water bodies in different ways, of different sizes and at different scales
How can these be compared, assessed and visualised/presented on a European-wide level
Data is collected, analysed, collated and submitted.
Traditional methods such as database queries will identify the water bodies of different status but tabular results difficult to interpret. How do you know that an area is generally improving or deteriorating?
Presentation of results is a key factor in generally assessing, compare and getting a feel for data.
Need to then present, assess and disseminate this information
Need spatial representation of the results.

4. GIS Guidance recommends use of a common geometry at EU level for water information reporting
Harmonised and coherent view of data
Facilitates de-centralisation
Usable by all involved parties (DG ENV, EEA, Eurostat)

5. Perception
Perception that common dataset needs to provide a spatially accurate representation of each and every water body
Data must be provided for each water body or group of water bodies, but this doesn’t mean that each and every water body must be spatially represented.
Purpose of common dataset is mainly visualisation aid – to present the data and see the changes over time

6. Purpose of Common Dataset
To provide a cartographic index to the more detailed water body data
To provide a stable base against which temporal change can be visualised
Dataset to report against NOT against which MS collate and assess their water bodies
Water body status, and possibly the water bodies themselves will change over time - main purpose of the map is to present the data and to facilitate this over time and provide a stable base.
Status of the water bodies over time can be reported as a spreadsheet format for example. Link common features to the unique ids for each water body
Supplements traditional tabular views of data – can see how the status of water bodies relates geographically.
More important not a dataset that MS must collate and assess.

7. Will apply regardless of the dataset used
Technical Issues
How to relate water bodies to features on common map so that the common feature can be used to access the water body data.
How to symbolize the map features to reflect the status of water bodies and the pressures and impacts acting upon them
Will apply regardless of the dataset used
There are technical issues which must be overcome and these will apply regardless of the dataset selected as the common dataset.
These basically are:
How to link the features on the map so that the information relating to the appropriate/corresponding water bodies can be accessed
How to symbolise so that the map view provides an understandable representation of the underlying data.

8. One Common – Many WaterBodies

9. One Common – Many WaterBodies

10. One Common – Many WaterBodies

11. One Common – Many WaterBodies

12. Many Common – One Water Body

13. 2nd Challenge - Visualisation
If red indicates poor status how to reflect this?

14. Visualisation - Example 1
River segments shaded by the ‘worst’ status

15. Visualisation - Example 2
‘Less than Good’ as percentage of whole

16. Visualisation - Example 3
Catchments shaded by the ‘worst’ status

17. Visualisation - Example 4
‘Less than Good’ as percentage of whole

18. Visualisation - Example 5
Water Body centroids, diameter proportional to size

19. Other Considerations Monitoring Points Pressures and Impacts
Location will vary over time
Display as points related to the water body or group of water bodies
Pressures and Impacts
How are these presented
Can be against a feature or an area
May group similar water bodies and monitor representatively – need to identify which water bodies belong to a group of water bodies, not necessarily contiguous.

20. Advantages of Common dataset
Will enable temporal changes in status to be displayed
Requirements for graphical submissions will be minimised
Helps validate submissions
Supports harmonised assessment
Facilitates de-centralisation
Will apply regardless of the dataset used
Water bodies may change over time – this will occur as more information on pressures and impacts, and hence the assessment of risk of failing becomes available, as status changes and changes in monitoring points – linking water bodies to a static base will help the effects to be minimised
Possibly more work up front but thereafter data can be submitted in tabular/spreadsheet format with a link to the common feature, will minimise requirements for graphical submissions. Will only be required as supplementary/explanatory information
Will help in the cross-checking of submitted data. Provides ‘ball-park figures for lengths and areas, and indicates where feature likely to be found .
Takes out scale variance
Facilitates de-centralisation – can provide id ‘hook’ into national systems, possibly web-based national systems.

21. Creating the Common Dataset
Ensure that features exist in the common dataset for the water bodies to be linked to
Matching exercise required between the common dataset and the national water body datasets
Method likely to vary by Member State
Will apply regardless of the dataset used
Have identified the CCM as a suitable candidate as the common dataset. However there are problems and issues that need to be overcome. Most of these have been covered by other documents and will be covered later so wont go into these now.
The tasks necessary will apply regardless of the dataset chosen, so worth pulling these out now.
First task is to ensure that the common dataset provides enough information for the water bodies to be sensibly linked to.
How the matching will be carried out is likely to vary by each member state and will be a combination of the scale at which the MS holds their water bodies, the general quality of the CCM at the MS level, amount of ‘local knowledge’ required
First thoughts that need buffers around linear features etc, but may be more appropriate to match within CCM catchments and link to segments that way.

22. Possible Outcomes Urgent consideration where
Features are incorrect in the common dataset
Features are missing in the common dataset
For example in the CCM, large flat areas may not be well modelled
Artifical, heavily modified water features, overseas territories, level of detail insufficient for

23. Features in common dataset are incorrect
CCM Catchments
CCM River Segments
National Rivers
For example in the CCM, large flat areas may not be well modelled
Artifical, heavily modified water features, overseas territories, level of detail insufficient for

24. Features are missing in the common dataset
CCM Catchments
CCM River Segments
National Water Bodies
For example in the CCM, large flat areas may not be well modelled
Artifical, heavily modified water features, overseas territories, level of detail insufficient

25. Possible Outcomes MS believe their data is more appropriate
MS data is of better quality?
Is there any merit in this?
Don’t really need the extra detail as it doesn’t really provide any more especially at smaller scale
Only need to fix where wrong or fundamental missing .

26. National Borders Assess dataset on a country by country basis
Available dataset are hydrological
Need to be split by national borders
Need to agree national borders and coastlines
Slivers/small polygons generated
Issues where river/lake forms part of national boundary
Small polygons may be generated – may be slivers or valid water bodies. Need to be assessed / local knowledge

27. Managing Change Should remain stable for a number of years
Changes likely to occur
Need processes to ensure quality and harmonisation

28. In Summary Need a common dataset Establish common dataset
Cartographic index
Matching to member state data
Resolve visualisation
Establish common dataset
Correct errors
Resolve national borders
Set in place maintenance processes

29. Actions Agree the need for a common dataset
Agree how this is to be built up
Available datasets, procedures for quality and acceptance, harmonisation, maintain intelligence and cross-border harmonisation
Agree national and coastal boundaries
Agree review period, manual changes

30. Cartographic Index MEMBER STATE DATASET COMMON DATASET ID MS_ID A 1
MS_ID STATUS LENGTH
1 High
2 High
3 Good
4 Poor
5 Good
6 Moderate
7 Moderate
Example where the Member state water bodies are defined at a larger scale.
This would generate a one-to-many relationship between the common dataset and the MS dataset – can access the water body data through the common feature. Detailed data eventually to be stored on MS systems but could be held on central system.
True lengths would be those defined by the MS dataset.
CONVERSE applies – issue with reported lengths
Water body 4 is of poor status – how can this be displayed?
Colouring whole of A red will provide misleading interpretation, especially for MS with more detailed water bodies