Problems arising during the implementation of CLC2006

Transcription

1 Problems arising during the implementation of CLC2006 George Büttner, Barbara Kosztra ETC-LUSI / FÖMI (HU) EIONET WG meeting on Land Monitoring IGN Portugal, March 2010

2 Contents of presentation Present status Main problems during implementation Technical solutions by countries Thematic context: nomenclature Spatial context: geometry Verification: change mapping Summary

3 CLC2006 production has officially finished (mid-february 2010) 36 out of 39 countries have finished 93 % of planned area 5,438 Mkm 2 Countries still in progress: Switzerland UK Not started: Greece Technical work started: May 2007 Technical work finished: February 2010 Total duration: 33 months

4 Main problems during implementation 1. Long administrative preparation, including financial commitment is some countries (e.g. DE, IT.. GR). 2. Elongated implementation time in some countries due to difficulties in providing national contribution (e.g. AT, HU, UK ). 3. Long GIS integration phase (several months) in some countries (e.g. ES, NO..) 1. Positive examples of fast (5-8 months) implementation in some larger countries: FR, PL, TR...

5 Technical solutions by countries AL AT+LI BE BA BG CR CY CZ DK EE FI FR DE HU IS IE IT LV image processing and GIS (incl. change mapping) GIS integration and photointerpretation LT LU MK MT MN NL NO PL PT RO RS+KV SK SI ES SE CH TR GIS and photointerpretation GIS and photointerpretation and GIS UK Generalisation of hi-res national LC database

6 Thematic context: nomenclature Generally no problems, just some difficulties: Non-consequent separation of pastures (231) and natural grasslands (321) in many countries. Non-consequent separation of arable land (211), pastures (231) and complex cultivation (242) in some parts of Europe. Missing class for degraded grasslands (neither 231 nor 321). Difficulty of separation of shrubby vegetation classes (322, 323) from each other and from transitional woodland-shrub (324) in several regions of Europe. Missing class for no current use in built-up areas. Irrigated land (212) is an inconsistently used class (instead of being a class would be better to be included as an attribute).

7 Example (-): 231 / 321 (DE) 231 and 321 next to each other in flat terrain and agricultural environment - not correct

8 Example (+): 231 / 321 (IS) 231: field structure, flat terrain; 321: no fields, hillside correct

9 Example (-): 322 / 323 (ES/AR) 322 and 323 require different environmental conditions - not correct

10 Irrigated land (?) orchards in ES/CA According to nomenclature 222, but also heavily irrigated area

11 Spatial context: geometry The 100 m positional accuracy is kept rather well (lower accuracy in some countries / regions). Polygons are usually meaningful, i.e. the 25 ha MMU is properly used. Consequently: CLC polygons in most countries would be suitable objects to be filled with hi-res information or new attributes.

12 Verification: change mapping Verification of national CLC-Changes datasets was important to achieve harmonised application of mapping rules and nomenclature, to provide comparable datasets by the countries, and to assure thematic quality of database. No conceptual problems in change mapping were observed. Not always the real change was mapped. The overall 5 ha rule was applied properly and did not overload the national teams. Technical Change was usually applied properly to compensate the effect of two different MMUs.

13 Verification: change mapping Typical problems in Class-1: New built-up (<25 ha) on urban fringe area is often miscoded; i.e is used instead of Construction sites are sometimes permanent (no associated change). Reclamation of dump- / mineral extraction / construction sites is frequently not mapped. Golf courses are often missed. New construction inside existing built-up is often not recognised.

14 Urbanisation (-) (DE) CLC2000 code is incorrect: the right process is and not

15 Verification: change mapping Typical problems in Class-2: Transitions between 211, 231 and 242 are often exaggerated or omitted. Multi-temporal information is not used properly. Proper mapping of new plantations (221, 222, 223) is possible only with high-resolution information. Mapping changes between 242 and 112 is usually subjective and affected by resolution differences. Changes of heterogeneous classes (242, 243, 244) are often overestimated/false/subjective.

16 Plantations Landsat TM / SPOT HRG (+) (ES/CM) In order to recognise plantations hi-resolution imagery is needed

17 Mosaic-like agriculture (-) (IT/EMR) The change is probably not true. What is the process here?

18 Verification: change mapping Typical problems in Class-3: While forest clearcut is usually evident, mapping of forest growth is frequently difficult, especially in Scandinavia. By using off-season (spring/autumn) images often false changes are mapped in forests. Mapping changes between shrubs (322, 323) and forests (afforestation) require high-resolution data. Forest fire areas were often missed. In mapping the retreat of glaciers the potential of using multi-temporal satellite images (esp. those taken in late summer) is not fully exploited.

19 Forest (31x) or clearcut (324) (?) (FI) Interpretation of forest growth is sometimes strongly subjective

20 Verification: change mapping Typical problems in Class-4 and 5: Temporal changes related to wetlands in dry-climate areas are often mapped as land cover changes. Changes related to meandering rivers are not always mapped. Temporal changes related to rivers are sometimes mapped as land cover change. Temporal changes related to water level in reservoirs are sometimes mapped as land cover changes.

21 Wetlands - spring / late summer (TR) Although area looks rather different, no CLC change

22 Overall CLC-changes statistics ( ) All land cover changes (yearly % of national territory) Change PT CY HU IE EE LV CZ NL SK LT LU AL CR KO MK DK BA FR IS BE PL BG RS AT RO ME SI

23 Building LC database using existing datasets Based on experience of Scandinavian countries Pros: Replaces the work-intensive photointerpretation Reproducible, repeatable at required time intervals Good compatibility with source data Cons: Not all required data are collected Quality / age / existence of source data is critical Intelligent generalisation rules are required (national/eea) The optimal solution seems to consist of Combination of existing national datasets and RS/GIS RS-based visual quality control

24 Example: plan and reality (+) (ES/VA) Maps often include plans and not the real size/status of objects

25 Example: fore-dated maps (-) (NO) The date of the map and the date of realisation of object might be different (here: omitted change)

26 Example: underground construction (-) (SE) Adopting ancillary data without control : tunnel construction mapped as land cover change (Stockholm)

27 Summary CLC2006 has been finished in 36 of the 39 participating countries. The project provides updated CLC layer and a CLC-Changes layer for Mkm 2 area of Europe. The 33-month implementation time is too long for the EEA and should be shortened in any future updates. Countries applied photointerpretation dominated technology with different levels of GIS data support. There are points in the nomenclature where improvements are recommended to be done. Change mapping technology performed rather well. In future updates human work-load could be reduced using results of national surveys and those of GMES Land Monitoring Core Service.