Frequently Asked Questions

The SAFE are the data originally disseminated by the European Space Agency. The SAFE format is basically a ZIP file with a collection of XML and other files. Within the SAFE file, the spectral bands are presented in the native spatial resolution of the satellite sensor. On the other hand, in the NetCDF files all bands are interpolated to the spatial resolution of the band with the highest resolution. This provides and image stack that is easy to use in processing. Furthermore, the NetCDF files are also available through OPeNDAP allowing data to be streamed into applications without downloading files.

If the user want data in the native spatial resolution from the NetCDF files, data can be subsampled to the original spatial resolution without information loss since the interpolation used is nearest neighbor.

Another benefit of NetCDF is data can be aggregated in time or space using an application server. This will allow extraction of data from e.g. multiple Sentinel-2 tiles or a time series of one tile. This is however yet not implemented. In the current setup, the NetCDF files lack some of the auxiliary information provided in the SAFE files.

As NBS currently offers two interfaces to data, there are some differences in the machine interfaces between them. The DHUS software offers OpenSearch and Open Data Protocol (ODATA). The NBS test portal offers OPeNDAP, OGC WMS, and ODATA (through the DHUS interface). OAI-PMH is under implementation and configuration. OGC WCS and OpenSearch is under consideration and planning for the test portal.

OPenDAP allows users to access remote files with their favourite analysis and visualization client. Data does not have to be stored as NetCDF to be served through OPeNDAP, but data must be mapped to UNIDATA's Common Data Model. NOAA Earth System Research Laboratory maintains a good overview of clients capable of handling OPeNDAP.

This was due to a bug occuring when the search results contained datasets where the dataset landing page was undefined. This is a bug should be fixed now and to our knowledge and testing it does not occur anymore.  Please report incidents using the issue tracker if you receive such messages.

There are multiple reasons for this. Initially we had a problem with different file formats for the Sentinel-2 data we indexed. This caused trouble in the SAFE to NetCDF conversion. This issue is fixed. When this appears now it is related to the performance of the WMS server supporting the indexing. In order to handle the large volumes of data, the communication with the storage backend has been reconfigured. This reconfiguration is not fully completed yet and causes these errors currently

SAFE is a format developed by the European Space Agency for "archiving and conveying Earth observation data within the European Space Agency (ESA) archiving facilities and, potentially, within the archiving facilities of cooperating agencies.". Further information on the SAFE format is available at