The TanDEM-X 50m Forest/Non-Forest Map

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is an Earth observation radar mission that consists of a SAR interferometer built by two almost identical satellites flying in close formation. They have been acquiring data for the generation of the global Digital Elevation Model (DEM) between 2011 and 2015 in stripmap single polarization (HH) mode. For more information on the TanDEM-X mission, please visit the TanDEM-X project page.

The global dataset of quicklook images, representing a spatially averaged version of the original full resolution data at a ground independent pixel spacing of 50 m x 50 m, has been used for the generation of the TanDEM-X Forest/Non-Forest (FNF) Map. The TanDEM-X FNF Map offered here for download has therefore a pixel spacing of 1.6 arcseconds (arsec), which corresponds to approximately 50m at the equator.

This information page gives an overview about the basic product specifications of the TanDEM-X FNF Map and explains how to download the TanDEM-X 50m FNF data sets. The license terms for the use of the data is automatically accepted by downloading the data. At the end of this page, suggestions for further readings and literature, a FAQ, tips for software tools, and contact information can be found.

The following chapter gives a short overview about the essential products specifications of the TanDEM-X FNF Map. The TanDEM-X 50m FNF Map offered for download follows in the most aspects this specification. DLR recommends for in-depth reading the download of the latest TanDEM-X FNF Map specification document, which can be found here: TanDEM-X FNF Map Product Description.

Product File Structure

The TanDEM-X 50m FNF Map is delivered in a compressed ZIP (*zip) format. Each zip file contains a main folder and 2 subfolders. In the main folder there are:

1. The FNF Map quicklook raster file
2. The license agreement - english version
3. The license agreement - german version

1. FNF: The FNF Map raster layer
2. AUXFILES: The following information files:
1. Coverage map
2. Super pixels date map
3. Super pixels count map
4. Acquisition information text file

Raster Values of the FNF Map Layer

The raster values in the FNF Map GeoTIFF file are:

0: invalid pixels and settlements
1: forested areas
2: non-forested areas
3: water bodies

For further details on the raster values for the auxiliary information layers, see the TanDEM-X FNF Map Product Description.

To get access to the products, you accept the user license, which can be found as PDF document here:

User License

Downloading Products

For the downloading of TanDEM-X 50m FNF products three options (either via HTTPS or FTPES), are available, depending on your preferences, your machine, your system settings and the amount of data you want to download. Solely encrypted connections are supported; plain HTTP or FTP download methods are not supported.

1. Option A: HTTPS Web browser & map-based interface for selecting individual tiles.
2. Option B: HTTPS Web browser interface for selecting individual tiles directly by browsing the directory structure.
3. Option C: Using the STAC API for FNF to filter and access the data via a python script.

Option A – Using a HTTPS Web browser & map-based interface

This download option is recommended for users who wish to download a few products and who prefer the usage of a map driven interface for the selection of the products.

1. Enter the URL of the map interface in a new web browser tab:
   https://download.geoservice.dlr.de/FNF50
   

   
   

   

   The page will appear with basic information about the TanDEM-X mission on the left and the map interface (showing a color coded version of the TanDEM-X global Forest/Non-Forest Map) with the polygon outline for each individual tile on the right. You can alter the map layer(s) shown in the map with the icon in the top right corner above the map canvas. Zoom to your region of interest, if needed.

2. Select the desired products (=left-click with the mouse on the corresponding tile). The name of the product appears in a list on the left side.

   

   Alternatively you can also draw a search rectangle in order to download the products for a larger region of interest. Press the CTLR key on your keyboard while left-clicking with the mouse on a point and drag and draw the rectangle on the map. The search rectangle will be closed and the products will be selected, when you release the mouse button. Selected products appear on the left side of the page. You can remove single items from the list by selecting the trash bin icon associated which each item.

   

3. After the desired products have been selected, they can be saved on your computer file by file by clicking on the download icon associated to each item.

4. Optional: If you want to automate the download of a larger list of files you can select the ‘List’ icon to save the download list to an ASCII text file (with an absolute pathname for each file per line), or you can select the metalink icon to save the file list to an XML-like metalink file.

   

   The ASCII file list can then be fed to a command line FTP client (e.g. wget or cURL, which are included in numerous Linux distributions), or to a download manager (e.g. aria2). The following code examples will illustrate the usage of those command line tools. The final line of code might need some adaptions with respect to individual system settings (e.g. whether a proxy is needed), but might serve as a starting point.

   Suppose you have saved the list to the name ‘TDM50mFNF-url-list.txt’ to your current working directory and the download directory will be the current working directory as well, then the wget command would be the following one-liner:
   wget -i TDM50mFNF-url-list.txt --auth-no-challenge
   

   The cURL command line would be:
   curl $(printf ' -O %s' $(<TDM50mFNF-url-list.txt))
   

   or, alternatively
   xargs -a TDM50mFNF-url-list.txt -L1 curl -O

   The aria2 command line would be:
   aria2c -i TDM50mFNF-url-list.txt

   The metalink XML file can be fed to a download manager tool (e.g. aria2). Suppose you have saved the metalink to the file name ‘TDM50FNF.meta4’ in your current working directory, then the command line for aria2 would be:
   aria2c -M TDM50FNF.meta4
   

Option B: Using a HTTPS Web browser and browsing the directories

The files can be also accessed via HTTPS by entering the following URL path into your web browser: https://download.geoservice.dlr.de/FNF50/files/. Single files can be downloaded by clicking on the files.

Directory Structure on the FTP Server:

The main directory structure on the FTP server contains just a FNF main directory. In this directory all available TanDEM-X 50m FNF products including the FNF Map and the auxiliary files are stored in a compressed ZIP (*.zip) format. Go here, if you need the complete data set for a certain FNF tile.

The main directory FNF is organized in a hierarchical directory structure and it contains subdirectories. The first subdirectory level is based on latitudes, one separate directory for each latitude value; each latitude subdirectory is subdivided into further subdirectories for the longitude spaced by 10 degree. Only subdirectories actually containing FNF tiles are visible.

Example: the directory ‘/FNF50/files/N49/E010’ contains the following 10 zip files:

TDM_FNF_20_N49E010.zip
TDM_FNF_20_N49E011.zip
TDM_FNF_20_N49E012.zip
TDM_FNF_20_N49E013.zip
TDM_FNF_20_N49E014.zip
TDM_FNF_20_N49E015.zip
TDM_FNF_20_N49E016.zip
TDM_FNF_20_N49E017.zip
TDM_FNF_20_N49E018.zip
TDM_FNF_20_N49E019.zip

Option C: Using the STAC API for FNF to filter and access the data via a python script.

The files can be also accessed via a python script using the STAC API for the newly integrated FNF STAC Collection. With this API interface, the FNF data can be spatially filtered with coordinates or with the TanDEM-X typical Tile-IDs for longitude and latitude.

Example python code snippet:

		 
			 stacapi_endpoint = "https://geoservice.dlr.de/eoc/ogc/stac/v1"
			 FNF_collection = ["TDM_FNF_50"]
			 bbox = [8.0, 47.5, 12.5, 52.25]
			 
			 catalog = Client.open(url=stacapi_endpoint)
			 catalog
			 
			 stac_items_FNF = catalog.search(collections= FNF_collection, bbox=bbox).item_collection()
			 print(f"Found {len(stac_items_FNF):d} FNF datasets with a overlap for the following boundary box: \nbbox = [8.0, 47.75, 12.5, 52.25]")