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Conversions from national grid data to harmonized European grid data

Conversions from national grid data to harmonized European grid data. EFGS Lisbon 12-14 October 2011 Production and challenges Rina Tammisto, Senior Statistician , Statistics Finland Marja Tammilehto-Luode , Chief Adviser , Statistics Finland. Harmonization.

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Conversions from national grid data to harmonized European grid data

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  1. Conversionsfrom national grid data to harmonizedEuropeangrid data EFGS Lisbon 12-14 October 2011Production and challenges Rina Tammisto, Senior Statistician, Statistics Finland Marja Tammilehto-Luode, ChiefAdviser, Statistics Finland

  2. Harmonization Data harmonization Spatialharmonization A gridnet covers the whole of Europe • Source data • Georeferencednational data • DisaggregatedEuropean data • Methodsused • Aggregated • Disaggregated • Hybridmethod

  3. ETRS89-LAEA Grid NetDownloadable ZIP • http://www.efgs.info/data/GEOSTAT-1km-Grid.zip/view • Grid_ETRS89_LAEA_1K.shp • Abt. 500 Mt

  4. ETRS89-LAEA Grid Net ETRS89-TM35FIN Grid Net

  5. ETRS89-LAEA

  6. ETRS89-LAEA ETRS89-TM35FIN

  7. LAEA gridnet in relation to national gridnetin Finland LAEA gridnet in relation to national gridnet in Austria

  8. Differences in locations of grid cells in different projections (or co-ordinate systems) • A grid cell produced by using the national ETRS89-TM35FIN co-ordinate system and projection is divided among several ETRS89-LAEA grid cells • Direct derivation between different co-ordinate systems or projection is not usable • grids are located differently in relation to each others A issue to be solved: How to use national griddatasetswhile the directconversion is notrelevant…?

  9. Tested method 1. Aggregation of grid data by using converted building points • 1) Georeferencedsource data is converted • Buildingsareconvertedfrom ETRS89-TM35FIN to ETRS89-LAEA • 2) Convertedbuildingpointsarejoinedwith the ETRS89-LAEA gridnet • 3) Aggregation of statistical data

  10. Building points in ETRS89-TM35FIN Building points in ETRS89-LAEA Aggregation of statistical data

  11. Method 1 Advantages Disadvantages Doublesets of primary data Doubleproductionprocessesfrom the beginning Risk of data disclosure – due to use of severalco-ordinatesystems- gapsbetweendatasets • Pointseasilyconvertible –originalquality of locationmaintained • Fromgeostatisticalpoint of view data qualitythroughly the same as in national data

  12. Testedmethod 2. Conversion of grid data by using ready-made national grid datasets • 1) Ready-made national griddataset in ETRS89-TM35FIN is converted into ETRS89-LAEA • Polygon to Point – using the middlepoints of national gridcells • Conversion of the middlepoints of grids • 2) Convertedpointsarejoinedwith the ETRS89-LAEA gridnet • 3) Aggregation of statistical data

  13. PRODUCTION OF THE NATIONAL GRID DATA CONVERSION OF THE POINTS, SPATIAL JOIN WITH ETRS89-LAEA GRID NET MIDDLE POINTS OF NATIONAL GRIDS AGGREGATION OF STATISTICAL DATA

  14. Effects of the grid cell size on the quality of the conducted data • Testedgridcellsizes: National grid data: - 125 m x 125 m – highestresolution data - 250 m x 250 m - 1 km x 1 km Reference data: Data producedbyusingmethod 1; (conversion made on buildingpoints) Additionaltest: JRC/GISCO disaggregated data – data produced for the Finnish Grid Database

  15. 1 km²/250 m

  16. 250 m

  17. 250 m

  18. 250 m ETRS89-LAEA from 250 m grids

  19. 125 m

  20. 125 m ETRS89-LAEA from125 m grids

  21. ETRS89-LAEA frombuildingpoints ETRS89-LAEA from 1 km grids ETRS89-LAEA from125 m grids ETRS89-LAEA from 250 m grids POP/KM²

  22. Comparison of the testdatasets • Statistics: • Number of grids, mean (inhabitants/gridpopulatedgridcell), totalnumber of inhabitants in the dataset, min, max

  23. Datasetfromconvertedbuildingpoints Datasetfromconvertedgridpoints

  24. Identityline (the 45 degreeline) Values of converteddatasetin relation to values of national datasets 125 m ETRS89-LAEA from125 m grids 250 m ETRS89-LAEA from250 m grids 1 km ETRS89-LAEA from1 km grids ETRS89-LAEA frombuildingpoints ETRS89-LAEA frombuildingpoints Evaluation of differencesbyusingabsolutevalues of inhabitants/km² gridcell(absolutevalues of differences) ETRS89-LAEA frombuildingpoints Dis.agg. ETRS89-LAEA disaggregate data ETRS89-LAEA frombuildingpoints

  25. DIFFERENCES (abs.values) betweenmethod 1 data (from LAEA buildings) to deriveddatasets DIFFERENCES (abs.values) betweenmethod 1 data (from LAEA buildings) to JRC/GISCOdisaggregated data

  26. Method 2 Advantages Disadvantages Geostatisticalpoint of view data quality is weakerthan the original national data Qualityerrors – qualitydistortioncompared to the correctone (measuringbynumber of inhabitants) • Use of the ready-madegriddatasets! • Lessphases • Smaller data mass • Level of quality is a matter of choice • Adequatelevel of quality (?) • Dependent on use • Min. target: SUM of the wholedataset is correct • No increase of confidentialityproblemswithdoubledatasets

  27. Nextsteps • For GEOSTAT 1A project from October - November 2011 • More tests, any volunteers? • Quality definitions concerning adequate level of quality and grid scale used • Step-by-step guidelines • LAEA dataset – filling the empty grid net with data!

  28. ThankYou! rina.tammisto@stat.fi marja.tammilehto-luode@stat.fi

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