1. A qualitative accuracy assessment Philippe Mayaux & the GLCers Institute for Environment and Sustainability, EC Joint Research Centre, Italy

2. The general approach Objective: to avoid macroscopic errors before the quantitative accuracy assessment Systematic descriptive protocol to document the verification per cell (± 220 km x 220 km) Use of ancillary data (maps, Landsat & SPOT images, aerial photographs…) and expert opinion Archive the evaluation in a database

3. The validation grid 40 N – 60 S: 2x2 degrees 40 N – 60 N: 2x3 degrees > 60 N: 2x4 degrees

4. The georeferencing system Alphanumeric Cell_ID Letter = latitude Number = longitude of left side

5. Qualitative evaluation fields Cell_ID Name of the expert GLC product Type of reference material: high-res image, quick-look, thematic map, aerial photograph, field photograph Number and nature of LC classes Spatial pattern: linear, diffuse, massive, insular Nature of limits: sharp, fuzzy Overall quality of the GLC product, very good, good, acceptable, unacceptable LC classes well-identified LC classes poorly identified Nature of problem: label, limit, missing class, other

6. Spatial patterns 4 main systems –Diffuse –Massive –Linear –Insular + combinations Dominant pattern within the cell

8. Quantitative accuracy assessment Objective : To provide a statistical assessment of the accuracy by class Components to evaluate: –over/under estimation of LC classes –wrong location Constraints : Budget (data, interpretation), time, number of classes, spatial complexity

9. The future Continuation of this validation exercise Involvement of other partners