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The FAQ applies to Terrascope and Proba-V MEP. Please note that the FAQ is in English only.

Frequently asked questions

Sentinel 2

What does the scene classification map look like?

All products are delivered together with the scene classification map, which gives an indication on the pixel quality of the delivered product. The different values and their meaning are given in the table below.

Table: Pixel quality classification map




























How do we derive NDVI and biophysical parameters?

“Terrascope offers ready-to-use information products derived from Sentinel-2 data. These include

  • NDVI – Normalised Vegetation Index
  • fAPAR – fraction of Absorbed Photosynthetically Active Radiation
  • fCOVER – fraction of Vegetation Cover
  • LAI – Leaf Area Index
  • CCC – Canopy Chlorophyll Content
  • CWC – Canopy Water Content

To learn more about how these products are produced, please read the TERRASCOPE SENTINEL-2  ALGORITHM THEORETICAL BASE DOCUMENT (ATBD) S2 – NDVI & BIOPAR – V200

What is the new version v200 of the Sentinel-2 workflow?

  • Level 2A Top-of-Canopy from the ESA Hub
    The base data is now Level 2A Top-of-Canopy (TOC) products, downloaded from the ESA hubs.
    Previously, we downloaded Level 1C products and applied the iCOR atmospheric correction to generate Top-of-Canopy products.
    This change ensures that we are in line with other platforms that offer the same data (e.g. DIAS platforms).
  • Sen2Cor for data continuity
    The archive (Benelux area) was reprocessed using the Sen2Cor atmospheric correction and topographic correction.
    Previously, we used iCOR for this. Both are valid processors which were extensively validated in intercomparison exercises (e.g. ACIX)
    This ensures data continuity in the time series.
  • Selection of downloaded data
    To ensure you only see data that are fit for use we now only download and offer data with less than 95% of cloud cover. This not only facilitates your search for useful data, but also reduces our data storage requirements. Furthermore, when we see dense clouds in the remaining tiles, we mask them out with a conservative buffer.
    This ensures that you only get to see data that are fit for use.
  • CCI land cover
    Using the CCI land cover package, the scene classification is now more reliable.
    This ensures that water, urban, and bare areas are more accurately classified, and that false snow detection is better handled.
  • No more cloud or cloud shadow masks
    We no longer offer cloud or cloud shadow masks, but you can still derive them from the scene classification data.
    This ensures that we do not offer data that is difficult to interpret.
  • Additional layers
    Additional to the Aerosol Optical Thickness (AOT) products you can now also access additional layers for improved further processing:

    • Water Vapor (WVP)

    • Solar Zenith Angle (SZA)

    • View Zenith Angle (VZA)

    • Relative Azimuth Angle (RAA)

  • More reliable data
    Using these additional layers, the calculation of vegetation indicators is now more robust. We also mask out pixels classified ad cloud, cloud shadow, snow, cirrus or saturated.
    This ensures that you only get reliable data.
  • ISO19115-2 compliant
    The INSPIRE metadata were revised and are now also compliant with the ISO19115-2 standard.

What are the general naming conventions and format of the Sentinel-2 products?

The naming conventions for the Sentinel 2 products are:




<MISSION>                       Mission ID (S2A/S2B)

<DATE>                            Start date of the segment identifier (format: YYYYMMDD)

<TIME>                             Start time (UTC) of the segment (format: hhmmss)

<GRIDID>                          ID of the granule/tile in UTM/WGS84 projection

<CONTENT>                      Content of the file. For details see the table below.

<RESOLUTION>                               Resolution of the product/file (not always available).

<VERSION>                                      Version identifier, three digits starting from ‘101’ for the first operational version

Example: S2A_20160908T105416Z_31UFS_FAPAR_10M_V101

Table: Possible values for the <CONTENT>




Top Of Canopy total product


Top of Canopy B01


Top of Canopy B02


Top of Canopy B03


Top of Canopy B04


Top of Canopy B05


Top of Canopy B06


Top of Canopy B07


Top of Canopy B08


Top of Canopy B8A


Top of Canopy B11

TOC-B12 Top of Canopy B12


Aerosol Optical Thickness


Solar Zenith Angle

VZA Viewing Zenith Angle
RAA Relative Azimuth Angle


Scene Classification file

QUICKLOOK Quicklook file
CCC Canopy Chlorophyll Content
CWC Canopy Water Content


Fraction of Absorbed Photosynthetically Active Radiation


Fraction of green Vegetation Cover


Leaf Area Index


Normalized Difference Vegetation Index


What is the file format of the Sentinel-2 radiometric products?

All Sentinel-2 image files are delivered in the GeoTIFF format. The accompanied metadata file is in XML format following the INSPIRE metadata standard (ISO19115-2).

The Sentinel-2 V200 TOC products include several files which are the output of the Sen2Cor processor for the atmospheric correction and Scene Classification.

The figure below shows the files included in the S2 TOC product.

Figure: S2 TOC product file list.

The S2 TOC Spectral Bands span from the visible and the Near Infra-Red to the Short Wave Infra-Red in different resolutions:

  • 4 bands at 10m;
  • 6 bands at 20m;
  • 1 band at 60m.

The AOT is provided in the native 60 m resolution.

Note that B09 and B10 are not delivered, as these contain the water vapor and cirrus bands, respectively .

More information on topics such as scaling from digital numbers to physical values, scene classification, data format, etc. can be found in the TOC products V200 ATBD.

What is the file format of the Sentinel-2 derived biophysical products?

All Sentinel-2 image files are delivered in GeoTIFF format. The accompanied metadata file is in XML format following the INSPIRE metadata standard (ISO19115).

VITO offers 6 Sentinel-2 vegetation indices or biophysical parameters: fAPAR, fCover, LAI, CCC, CWC and NDVI. All products of these vegetation indices contain 4 files. Three datafiles (the respective biophysical parameter, a quicklook image file, and the Scene Classification), as well as the earlier mentioned XML metadata file. The data are available at both 10 m and 20 m resolution.

The table below lists the technical information of the Sentinel-2 derived products providing information on how to calculate the Physical Values (PV) from the Digital Numbers (DN) available in the files. The PV can be calculated using the following formula:

Physical Value = Scaling * Digital Number + offset.

Table: Sentinel-2 derived vegetation products Physical Value and Digital Number data range, scaling, and offsets.






Physical min





Physical max





Digital number min





Digital number max















No data





Data type





Saturation min*





Saturation max**





*Values between saturation min and physical min will be set to physical min before quantization is applied.

** Values between saturation max and physical max will be set to physical max before quantization is applied.

More information on the biophysical parameters' retrieval methodologies can be found in the TERRASCOPE SENTINEL-2  ALGORITHM THEORETICAL BASE DOCUMENT (ATBD) S2 – NDVI & BIOPAR – V200



How to use the OGC WCS service?

This service is currently unavailable

Virtual Machines

How to access your Terrascope VM?

There are two ways to get access to your Terrascope VM: either by accessing the graphical desktop of your VM, or through the command line.

Graphical access is the easiest option if you are not comfortable with using a Linux terminal, but requires a stable and reasonably fast internet connection to the Terrascope cloud.

You can sign in using your Terrascope portal account. Make sure you use lowercase characters for your username: e.g. 'Username90' should be transformed to 'username90'.


How to access your VM is explained in the following videos.


Commandline access

Commandline access is provided though SSH. Download and install an SSH client (e.g. PuTTY for a Windows OS) if needed.

On Linux you can use the command: ssh -p port username@uservm.terrascope.be

If your ssh connection gets terminated or 'hangs' after a while of not using the connection, a fix could be to make a change in your local ssh settings.

By adding the 'ServerAliveInterval 60' to your ssh config and restarting your ssh daemon, the client will send a null packet to the server every 60 seconds to keep the connection alive. The '60' in the line is the amount of time in between each null packet.

Desktop access

The following steps are required to access the desktop

X2Go client installation

Download and install the X2Go client program for your operating system, as described here: http://wiki.x2go.org/doku.php/doc:installation:x2goclient

Create Toolbox VM session

Start the X2Go client and create a new session. The host, and ssh port is provided to you when requesting a new toolbox. The login and password is the same as for the Terrascope portal.

Make sure to select 'XFCE' as the session type at the bottom of the window. Other sessions types will not work unless you install them manually. XFCE is a lightweight desktop environment, which is suitable for use on virtual machines.

Also change the compression method to '4k-png' on the 'Connection' tab:

When this is done, you can click on Ok, and should be able to log into your VM. When successful, you end up in a desktop environment that looks like this:

The 'data' folder links to the entire Terrascope EO archive. The 'tiffdata' links to all the tiff files.


What is the VM backup policy?

Your user virtual machine is not backed up!

In line with other cloud environments, virtual machines should not be regarded as being persistent. This means that all data in your home directory and other system directories may be lost in case of a system failure.

To solve this, here are some suggestions:

  • Use version control for anything really important.
  • Use the 'Public' and 'Private' folder in your home directory, these are on a shared filesystem that is more persistent than regular folders, but also do not have snapshots. So if you remove or break a file, it would still be lost.

How to enable file sharing for your User VM?

X2GO also provides file sharing support between your own PC and the User VM. On the 'Shared folders' tab, add the local folder(s) you want to become available in your User VM.

Typically, you will want the folder to become available when the X2GO session is started. In that case, select the 'automount' option.

The local folder will be mounted using Fuse. The hard part is to locate the folder on the User VM on which the local folder is mounted. The easiest way to find out is to run the following command on the User VM:

[daemsd@daemsdvm ~]$ mount | grep x2go
dirkd@ on /tmp/.x2go-daemsd/media/disk/_home_dirkd_Documents type fuse.sshfs (rw,nosuid,nodev,relatime,user_id=30320,group_id=631600014,default_permissions)

This shows that the folder is mounted on /tmp/.x2go-daemsd/media/disk/_home_dirkd_Documents.

Note: the Windows X2GO client seems to generate the wrong type of SSH keys during installation (DSA iso RSA). If you experience problems to get filesharing support on Windows working this could be the cause. You can fix this by copying the DSA keys under C:\Users\<username>\.x2go\etc and replacing 'dsa' by 'rsa' in the filename. If you still experience problems, you can try to uninstall X2GO, remove the .x2go folder in your home directory and install the latest X2GO version. During the installation make sure you enable the debug output option. X2GO can now be started in debug mode, providing detailed log messages which are useful for us to resolve your problem.

How to manage user defined Aliases and Environment Variables?

Since the ~/.bashrc file is automatically managed, changes to this file will be reset.

To make sure users can still create aliases or set environment variables there is a file ~/.user_aliases which can be used for this reason. If this file doesn't exist yet, it can be created.

How to request a new Terrascope VM?

Note that you need to be signed in on the Terrascope portal using your Terrascope account to request an OpenStack Virtual Machine (VM).

After receiving your request for a VM, the Terrascope team will validate your request and provide you feedback within two working days and a VM when your request is granted.

You will receive an e-mail explaining how to access your personal VM.

Your VM with standard configuration (4 CPU,8GB RAM, 4GB SWAP, 80GB Root Disk) will be provided for free. If for specific projects or operational services more resources are needed in terms of CPU, RAM or storage, please do not hesitate to contact us at info@terrascope.be to see how we can further help you achieving your goals.

The Terrascope VM runs on the OpenStack private cloud hosted by VITO.

How to access your VM is explained in the following videos.

What is a user virtual machine?

With the user Virtual Machine (VM), a developer or researcher can access a Virtual Research Environment with access to the complete Terrascope data archive and a powerful set of tools and libraries to work with the data (e.g. SNAP toolbox, GRASS GIS, QGIS) or to develop-debug test applications (R, Python or Java).

The user Virtual Machine:

  • comes with several pre-installed commandline tools, desktop applications and developer tools which are useful for exploitation of  the data available in Terrascope  (e.g. GDAL, QGIS, GRASS GIS, SNAP, Python, etc ...).
  • provides access to the full Terrascope EO data archive. 
  • targets an audience of scientists and developers developing applications which use Terrascope EO data. After the prototyping phase, the Terrascope processing environment can be used for larger scale processing.

What are the costs for a Terrascope VM?

Your VM with standard configuration (4 CPU,8GB RAM, 4GB SWAP, 80GB Root Disk) can be provided for free.

If for specific projects or operational services more resources are needed in terms of CPU, RAM or storage, pleasse do not hesitate to contact VITO to see how we can further help you achieving your goals.

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