updated readme

Author: matthewhanson

README.md

@@ -17,25 +17,12 @@ While GeoLambda was initially intended for AWS Lambda it is also useful as a bas
 | 1.2.0     | 2.4.2 | Separate Python (3.7.4) image and Lambda Layer added |
 | 2.0.0		| 3.0.1 | libgeotiff 1.5.1, proj 6.2.0 |
 
-### Docker images
-
-The Docker images used to create the Lambda layer are also published to Docker Hub, and thus are also suitable for general use as a base image for geospatial applications. 
-
-The developmentseed/geolambda image in Docker Hub is tagged by version.
+#### Environment variables
 
-	$ docker pull developmentseed/geolambda:<version>
+When using GeoLambda some environment variables need to be set. These are set in the Docker image, but if using the Lambda Layer they will need to be set:
 
-Or just include it in your own Dockerfile as the base image.
-
-```
-FROM developmentseed/geolambda:<version>
-```
-
-The GeoLambda image does not have an entrypoint defined, so a command must be provided when you run it. This example will mount the current directory to /work and run the container interactively.
-
-	$ docker run --rm -v $PWD:/home/geolambda -it developmentseed/geolambda:latest /bin/bash
-
-All of the GDAL CLI tools are installed so could be run on images in the current directory.
+- GDAL_DATA=/opt/share/gdal
+- PROJ_LIB=/opt/share/proj   (only needed for GeoLambda 2.0.0+)
 
 ### Lambda Layers
 
@@ -86,6 +73,27 @@ See the [GeoLambda Python README](python/README.md). The Python Lambda Layer inc
 | eu-central-1 | arn:aws:lambda:eu-central-1:552188055668:layer:geolambda:1 |
 
 
+### Docker images
+
+The Docker images used to create the Lambda layer are also published to Docker Hub, and thus are also suitable for general use as a base image for geospatial applications. 
+
+The developmentseed/geolambda image in Docker Hub is tagged by version.
+
+	$ docker pull developmentseed/geolambda:<version>
+
+Or just include it in your own Dockerfile as the base image.
+
+```
+FROM developmentseed/geolambda:<version>
+```
+
+The GeoLambda image does not have an entrypoint defined, so a command must be provided when you run it. This example will mount the current directory to /work and run the container interactively.
+
+	$ docker run --rm -v $PWD:/home/geolambda -it developmentseed/geolambda:latest /bin/bash
+
+All of the GDAL CLI tools are installed so could be run on images in the current directory.
+
+
 ## Development
 
 Contributions to the geolambda project are encouraged. The goal is to provide a turnkey method for developing and deploying geospatial applications to AWS. The 'master' branch in this repository contains the current state as deployed to the Docker Hub images `developmentseed/geolambda:latest` and `devlopmentseed/geolambda-python:latest`, along with a tag of the version. The 'develop' branch is the development version and is not deployed to Docker Hub.