With our most recent project we came another step closer to the realisation that government geospatial projects are moving out of the 90′s. We were asked by a client to build an online modelling tool for evaluating risk resulting from a natural hazard such as an earthquake. Understanding risk requires identifying the hazard (e.g. Tsunami) and exposure (e.g. population in a coastal city).

Data on hazards and exposure forms inputs to the risk and impact models. Such data is normally under the custodianship of national governments, with the responsibility of custodianship often distributed across departments and agencies. Bringing the data together into a single modelling tool is not just a technically challenging task but also requires cooperation and sharing of data across agencies. And anyone who’s worked in government knows this is often harder to do than solving the engineering challenges. We were very fortunate to have the involved custodians onboard with an eagerness to learn and deploy new technologies.

Back in the 90′s such hazard models would be run on a desktop with access to the data via a local disc copied from all the DVD’s posted by the data custodians using snail-mail.

This was a fine solution back in the 90′s but in the 21st century, quite frankly, it starts to look embarrassing. Our proposed solution was a distributed architecture which pulled hazard and exposure data using OGC web services and ran the model on a modelling server that could be scaled. The modelling server pushed the results of the run to another OGC compliant server. This is a simplified drawing of the architecture:

Once the model run was complete the client was notified via websockets. Here is the final application in action:

If you can’t access the video below – you may download the 16MB m4v file here or 10MB for the iphone.

Cool eh! With all these moving parts we needed to ensure that the various services were being monitored. Introducing Monit. If you haven’t heard of Monit check it out here: System Monitoring With Monit. It keeps tabs on your server daemons. If you have any questions feel free to post in the comments or get in touch via email.

… and I am in Berlin, if you are in town come say hi.

Since Haiti I have been doing a lot of reading on disaster response and recovery. Today I needed to load a GeoRSS feed from USGS. They publish the location of earthquakes as a GeoRSS feed. They also publish a product called ShakeMaps. This is a fantastic product since it provides a map of the actual “ground shaking” a not just the simplistic magnitude and epicentre. Creating a ShakeMap is a function of local geology, epicentre, magnitude and many other variables. You can read about it here. ShakeMap are thus much more useful from a disaster response and recovery point-of-view. For example if you have the necessary data on geology and population exposure you can run a model that simulates an earthquake over a region to predict the likely effect on the population.

Getting back to the GeoRSS – the ShakeMap feed allows us to integrate this into any web mapping application thus creating interesting mashups. E.g. overlaying it with socio-economic or population exposure or vulnerability data to show the simulation results I mention above.

Okay so I’ll show you how to set up a GeoRSS feed parser using Sinatra. Here is the ShakeMap as GeoRSS Feed. You will need ruby and sinatra installed.

Here is the code for the routes in sinatra:

require 'rubygems'
require 'sinatra'
require 'open-uri'

get '/' do
  haml :shakemaps
end

get '/proxy' do
  open params["url"]
end

When the client hits the our root url (/) we will render the OpenLayers map with the USGS ShakeMap. We may also want to let people add other feeds.

So in our shakemaps.rb the first route is to the root. This is pretty simple, when the root of the app is hit the server renders the shakemaps haml template. The haml template loads our javascript to render the OpenLayers map. This javascript also calls the shakemap GeoRSS feed via a proxy. The proxy is needed because OpenLayers which is a javascript library isn’t allowed cross-site-server calls. The proxy is where the second method in shakemaps.rb comes along. It looks for the parameter url at the end of the URI and simply opens it. This is the GeoRSS XML feed. Finally there is a form allowing us to point to other GeoRSS feeds.

• Demo here
• Code here