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Transformation of gridded reporting data from national grids to the INSPIRE Equal Area Grid

The INSPIRE 'Equal Area Grid' is mainly intended for spatial analysis or reporting purposes (e.g. statistical information) - not for communities where the grids have to be optimized for data exchange, supercomputer processing and high volume archiving of new data each day.

Existing reporting data in Members States is often obtained and referenced to national grid systems, adapted to both, the legislation and needs in each country. Transformation of such kind of data to the European Equal Area Grid defined in the INSPIRE context is therefore a challenge for Member States when implementing the Directive.

Two types of aspects have to be considered in the transformation:

  • Thematic aspects - Involving how each type of variable have to be resampled, including data quality considerations, etc. - They have to be dealt by the specific thematic community (i.e. in other Thematic Cluster).
  • Transformation process aspects - Involving how to map data from the national grid system to the Equal Area Grid in each Member State - They have to be dealt by the GG Theme & Thematic Cluster. It would be desirable to automate this kind of tasks, as possible.

Is there any valuable experience in Member States that may guide or serve the others as example of data transformation?

  • Juan Manuel VILLARES

    By Juan Manuel VILLARES

    In the Data Bank of Nature (Ministry of Agriculture, Food and Environment of Spain), we have developed a simple method for transforming our national data on species distribution, collected in a 10x10 km grid in the UTM ETRS89 H30 system to its equivalent 10x10 km. grid in ETRS LAEA system.

    This is a method based on sampling. The original data are overlapped by a LAEA grid with the smallest cell size available (always smaller than the original one).

    The more accurate is the chosen grid, the better.

    The method consists on overlay the grid LAEA over our local grid (ETRS89), selecting every LAEA cell that intersect with the cells of the ETRS89 grid.

    In our case, we have overlapped a 1x1 km LAEA grid over our 10x10 km ETRS89 H30 grid.

    Since the coding of 1x1 cells, includes the reference to 10x10, we dissolved the cells to transform our selection into a LAEA 10x10 grid.

    As a result, we obtain both whole cells and some partial cells that we have to decide if they are assumed or discarded. In our test we used the 50% of covered surface criterion but this criterion can vary depending on what the mapping represents and whether it has to overestimate or underestimate the number of cells.

    Error will be minimized if we use a LAEA grid with the smallest cell size possible. So, if we had used 500x500 m. or even 100x100 m. instead of using the 1x1 km grid, we had reduced error but always at the expense of slowing down the process and increasing the computing operations.

    In the case of species distribution, we have varied the percentage of decision depending on whether the species is abundant (it doesn’t matter if we underestimate a little) or is a rare species (in this case, can not miss any cell)

    We have developed a program that automates the process (for distribution of species and habitats only) requesting a number of parameters to refine the transformation.

    It would be great to implement a transformation service because it is clear that the units responsible for habitat and species inventories (at least in our Ministry) will not work with LAEA grid because they don’t want to lose the historical series.

    Here you can find a video of the process

    I hope that our experience could help.

  • Jordi ESCRIU

    Dear members,

    I will wait 1 week in case there is any additional experience or issue in the Member States regarding the transformation of existing reporting data obtained and referenced to national grid systems, to the European INSPIRE Equal Area Grid.

    In case there is not activity in this period, I will proceed to close the discussion topic.

    Jordi

  • Jordi ESCRIU

    Dear colleagues,

    As mentioned last week, I proceed to close this topic.

    Jordi

This discussion is closed.

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Elevation, Ortho & Grids

Elevation, Ortho & Grids

INSPIRE Thematic Cluster Elevation, Orthoimagery, Reference systems, Geographical grids - Join this group to share your knowkledge, learn and collaborate in solving issues related to the Elevation, Orthoimagery, Reference systems and Geographical grids themes