diff --git a/README.rst b/README.rst
index beab8eae559d925591f0fbb88a6d00c41610155d..e9a7be18f561614cb09b59c6b26b699dfe401fff 100644
--- a/README.rst
+++ b/README.rst
@@ -20,6 +20,8 @@ Requirements
 
 The toolbox is based on python 3 and has been tested until python 3.7 version so far. In addition to standard python packages it uses the `icedrift <https://gitlab.awi.de/floenavi-crs/icedrift/>`_ package for the coordinate transformation. 
 
+A internet connection is required when using the Polarstern as reference station as reference data is automatically queried from a REST interface. 
+
 Installation
 ------------