Update the README

README.md

@@ -1,10 +1,37 @@
-# Dockerfile for GDAL
+# GDAL Docker Images
 
-This contains a Dockerfile which creates an Ubuntu derived docker
-image.  The image contains the latest GDAL github checkout compiled
-with a broad range of drivers.  The build process closely follows that
-defined in <https://github.com/OSGeo/gdal/blob/trunk/.travis.yml> but
+This is an Ubuntu derived image containing the Geospatial Data Abstraction
+Library (GDAL) compiled with a broad range of drivers. The build process
+closely follows that defined in the
+[GDAL TravisCI tests](https://github.com/OSGeo/gdal/blob/trunk/.travis.yml) but
 omits Java support.
 
-See the [Docker Index](https://index.docker.io/u/homme/gdal) for more
-information.
+Each branch in the git repository corresponds to a supported GDAL version
+(e.g. `1.11.0`) with the master branch following GDAL master. These branch
+names are reflected in the image tags on the Docker Index (e.g. branch `1.11.0`
+corresponds to the image `homme/gdal:v1.11.0`).
+
+## Usage
+
+The following command will open a bash shell in an Ubuntu based environment
+with GDAL available:
+
+    docker run -t -i homme/gdal:latest /bin/bash
+
+Running the container without any arguments will by default run the GDAL test
+suite:
+
+    docker run homme/gdal:latest
+
+You will most likely want to work with data on the host system from within the
+docker container, in which case run the container with the -v option. This
+mounts a host directory inside the container; the following invocation maps the
+host's /tmp to /data in the container:
+
+    docker run -v /tmp:/data -t -i homme/gdal:latest /bin/bash
+
+Note that the with the image tagged `latest`, GDAL represents the latest code
+*at the time the image was built*. If you want to include the most up-to-date
+commits then build the docker image yourself locally along these lines:
+
+    docker build -t gdal:latest git://github.com/geo-data/gdal-docker/