Updated documentation.

docs/source/installation.rst

@@ -5,19 +5,27 @@ Installation
 Installing sen2chain
 --------------------
 
-This package requires Python 3, GDAL, OTB and `Sen2Cor <http://step.esa.int/main/third-party-plugins-2/sen2cor/>`_.
+This package requires pip3, Python 3, GDAL, OTB and `Sen2Cor <http://step.esa.int/main/third-party-plugins-2/sen2cor/>`_.
 
 .. note:: The current version of sen2chain is not available on Windows.
 
 
 Prerequisites
 ^^^^^^^^^^^^^
-GDAL and OTB
+pip3, GDAL and OTB
 
 .. code-block:: console
 
-    sudo apt install gdal-bin libgdal-dev python3-gdal otb-bin python3-otb
+    sudo apt install gdal-bin libgdal-dev python3-gdal otb-bin python3-otb python3-pip
     
+As indicated in the `OTB installation <https://www.orfeo-toolbox.org/CookBook/Installation.html#linux-x86-64>`_, do not forget to initialize the environment when you launch a new terminal with
+
+.. code-block:: console
+
+    source otbenv.profile
+
+
+
 Sen2Cor
 
 .. code-block:: console

requirements.txt

@@ -9,4 +9,5 @@ sentinelsat>=0.12.2
 pyproj>=1.9.5.1
 typing>=3.6.6
 pandas>=0.23.4
+urllib3>=1.22