ETS Sampling zones
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Representativeness of the sampling
ECA’s Special Report 25/2016 on the performance of LPIS recommended to carry out a cost-benefit analysis to determine whether quality assessment could be improved to achieve better coverage of parcels. The results of this analysis have lead to some changes in the sampling procedure that were implemented from 2017 onwards.
As mandated by the Regulations (Article 6.2 of (EU) Regulation No 640/2014), the LPIS QA zones and reference parcels are selected and defined by the EC services.
In collaboration with the contracted image provider, a procedure has been designed to achieve a number benefits compared to the CwRS-image coupling from ETS v5.3.
General goal is to reach imagery of sufficient quality to serve as a true reference for the current situation on the ground with an unbiased sampling.
Different criteria have been taken into account:
- an equal probability of inspection for all reference parcels while preventing the exclusion of zones and bias
- independence from CwRS zoning, further ensuring absence of bias
- improved geometric and radiometric image quality by means of
- related timing of capture when cloud and haze free conditions arrive
- restricting image capture to near-nadir conditions
- using sensors with a Ground Sampling Distance (GSD) of 50cm or less
- concentration of field activities in a few representative locations, lowering the resources needed for the inspection process.
In practice, the zone selection procedures operates through a 4 level stratification based on reference parcel abundance and agricultural area representativeness. These two parameters are derived from the LPIS populations uploaded by the custodians for the previous LPIS quality assessment. The resulting 87 image zones are shown in Figure 1.
- Figure 1: LPIS QA data capture zones over EU
In Figure 1, each color represents a zone where a one or more images will be acquired. Additional imagery may be acquired in a given zone to reach the minimum sample size. Special imagery is captured in low reference parcel density zones.
Reference Parcel Sampling
This sample of reference parcels to be inspected in the ETS will be generated in the intersection of the LPIS QA zones acquired as above and the full population of reference parcels ( scope of the quality assessment). In practise this means that LPIS custodians have to upload their population to the LPIS QA portal so this sampling can be generated by DGJRC.
In order to receive a sample pre-selection Member States shall:
- do Steps 2, 3 and 4;
- download the sample pre-selection list in Step 9.
To ensure correct timing of this assessment, upload of population data to DGJRC will be possible only from the last date of submittal of applications, in line with Article 13(1) of (EU) Regulation No 809/2014. "Member States shall fix the final dates by which the single application, aid applications or payment claims shall be submitted. The final dates shall not be later than 15 May each year. However, Estonia, Latvia, Lithuania, Finland and Sweden may fix a later date which shall not be later than 15 June.".
There is no particular deadline for the uploading of the 2017 LPIS QA population by the EU MS. However, the LPIS QA imagery acquired by JRC, is still delivered to the MS administrations together with their sample pre-selection as a bundle, which means that the source imagery can be obtained only after a valid population upload is made. The deadline for the production of the assessment report remains January 31st, 2018 as laid down in the Regulations.
DGJRC will produce the sample within 15 days after LpisPointZeroState upload.
Population data and sample exchange instructions
Creating the sample pre-selection requires:
- Step 1 (by EC): prepare LPIS Control Zones data:
- ApplicableLpisqaZones.xsd (GML)
- ApplicableCidZones.xsd (XML) – in exceptional cases as contingency measure
- Step 2 (by MS): create a point representation from the reference parcel polygons (total population of parcels from the Lot);
- Step 3 (by MS): convert reference parcels' point data into a harmonised data structure: LpisPointZeroState.xsd,
- Step 4 (by MS): upload the LPISPointZeroState through the LPIS QA Web Application. For instructions, go to:
- Step 5 (by EC): receive and analyse reference parcel data and LPIS Control Zones data (by EC),
- Step 6 (by EC): select reference parcel points which are within the LPIS control zones,
- Step 7' (by EC): determine the sample size for the ETS inspection, based ISO 2859/2-1985, procedure A,
- Step 8 (by EC): generate a sequential list of randomly selected reference parcels, and send a notification e-mail. See details on
- Step 9 (by MS): download the pre-selection list LpisSamplePreselectionStatus.xsd For instruction go to:
This methodology is presented in diagram 1, below.
- Diagram 1 Workflow of the ETS sampling methodology.
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