Experience from Czech Republic - September 2017

Description

Process followed to implement an Elevation TIN dataset in Czech Republic according to the INSPIRE Data specification on Elevation, transforming source data from the national DTM.

Implementation of data using TIN spatial representation type is optional in INSPIRE, and is an additional step after the transformation of grid Elevation data set already performed I 2015 by the same organization.

• Source data: DTM from the Czech Republic obtained from airborne laser scanning, with a vertical accuracy standard error of 0.3 m in bare terrain and 1 m in forest areas, available in XYZ format, where Z values are available in 2 different vertical references (EPSG:5514 and EPSG:5705). Size of the source data set is 280 GB.

• Transformation procedure - Composed of 2 steps:

a) CRS transformation to 2D geodetic ETRS89 plus EVRS height, and;

b) Format transformation to GM_Tin (ISO 19197), implemented with gml:TIN structure. Examples of encoding are available, using 2 alternatives: implementing gml:posList and gml:pos.

• INSPIRE data provision: currently evaluating the possibility to use predefined datasets or direct access download service.

Data themes covered

Elevation.

Status

On-going.

Issues / Conclusions

• Huge increase of volume after harmonization – From 280 GB of source data set to 4,5 TB of TIN data using the most effective implementation (using gml:postList), and to 10 TB using the less effective implementation (using gml:pos).
• Ability of most GIS clients to read gml:TIN is questioned.
• This may cause problems in using direct access download services to serve TIN data.

Resource

https://inspire.ec.europa.eu/sites/default/files/presentations/KusovaVeronikaTIN.pdf