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

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

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

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

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

LUCAS 2009-2012 photo-interpreted points

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

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

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

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

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

Zoom on the sample: Alpes Scandinavia

LUCAS 2015 Subsampling rates  

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

Covering excluded areas An additional sample to be photo-interpreted should be selected on the excluded points Including 2009 and mainly 2012