1. Sampling scheme for LUCAS 2015
J. Gallego, JRC-MARS

2. Reminder: LUCAS 2001-2003 two-stage sampling
One cluster every 18x18 km
Each cluster has 5 x 2 points 300m apart from each other.
And one transect of 1200 m that joins one row of points
It can be seen as an incomplete observation of a segment
PSUs SSUs

3. LUCAS 2006 two-phase sampling
First phase: Systematic sampling of unclustered points (single stage)
A master or first phase sample (pre-sample): One point every 2x2 km
Stratification by quick photo-interpretation
Second Stratified sub-sampling
Priority: crop area
50% in cropland strata
40% in grassland
10% other strata
Excluded areas > 1200 m altitude
11 countries covered

4. LUCAS 2009
First phase sample: same 2-km grid as 2006 extended to EU25-(MT, CY)
Excluded points:
Altitude > 1000 m.
Minor islands
Subsampling rates tuned by stratum and NUTS2
A large number of points could not be reached and was photo-interpreted
Office (ex-ante) >29,000
Field > 29,000

5. LUCAS 2012
EU-27
Non-eligible points: approx. 340,000 points are excluded from the second phase sampling for the field survey.
Altitude > 1500 m.
Minor islands
Points photo-interpreted ex-ante in 2009 because they were considered too difficult to be reached.
Points photo-interpreted in the field in 2009 were substituted by other points in the same NUTS2*strata with better accessibility
Other points too far from the roads or too strong elevation change.
Thresholds computed by NUTS0

6. LUCAS 2009-2012 photo-interpreted points

7. LUCAS 2015 EU-28 Keep 2012 rules on:
Altitude (>1500 m)
Points that could not be reached in a previous survey
Distance thresholds to be applied only in “CLC-difficult-access” areas.
Threshold distance to road: 600 m
Threshold altitude change: 100 m
Non-eligible points reduced from 340,000 to 167,000 points

8. LUCAS 2015 master grid (1st phase sample)
Filling gaps on previous version
Making it consistent with NUTS 2010 layer
+ Transitional waters (outside NUTS boundaries).
Sampled but weight =0 for estimation
Homogeneity across countries might need to be improved
Transisional waters in LUCAS 2015 grid

9. CLC-difficult access
Assumption: Agricultural areas are generally reachable by car, even if dirt roads are not reported in Tele-Atlas.
CLC classes assumed to have easy accessibility:
1** : artificial
2** : agricultural

10. Distance to closest road
Based on Tele-Atlas
Agricultural dirt-roads not included

11. Types of non-eligible points
Visual impression may be misleading (15% of points non-eligible)

12. Zoom on the sample: Alpes Scandinavia

13. LUCAS 2015 Subsampling rates

14. Subsampling: additional modifications
Minimum sample nh=2 per domain (NUTS2 * stratum)
Some points selected by the Soil Bureau were forced to belong to the sample.
The full 1st phase sample was selected for CY and MT

15. Covering excluded areas
An additional sample to be photo-interpreted should be selected on the excluded points
Including 2015, 2012 and 2009
Work ongoing
Adapting nomenclature to photo-interpretation
Elaborating precise rules for a consistent photo-interpretation