MapTube and Streaming Google Earth – Sharing Data via Anonymous Servers

Richard Milton and Andrew Hudson-SmithCASA, UCL

UCL CENTRE FOR ADVANCED SPATIAL ANALYSIS

Google Earth and Google Maps have changed the nature of sharing Geographical Information to such an extent that the ability to view data from a global to street level is now often taken for granted.

Sharing data in Google Maps is not however an easy task, it still requires significant skills in GIS. MapTube, developed as part of the GeoVUE project, aims to address this with a simple click through interface, allowing users to share any data. In a similar way to YouTube, the data is held on an external server, opening up the possibility of a central map resource and data sharing.

We preview MapTube in this seminar as well as detailing the latest work on Virtual London and Google Earth.

New Google Earth Features

• Network links and LODs– eSociety ..\data\DUG-examples\eSociety\mapstest.kmz– 13.7MB, 10,921 files– Virtual London ..\data\DUG-examples\Westminster.kml– 3.3GB, 2,337 files

• Animation Bars• Geocoding

The Maptube Idea

• Publishing geospatial datasets on the internet requires a map to put the data on.• Using Google Maps, data can be hosted legally.• Building custom tile layers for Google Maps that render data on the fly requires code that

executes on the server and can be very slow.• Most users do not have access to a programmable server e.g. ISPs and Google Pages.• So why not pre-render all the tiles, remove the programmable server component, speed

up the map rendering and give everybody the ability to host geospatial data on their own website?

• Because there are a lot of tiles (274,877,906,944 at zoom level 19) …• …but data tends to fall into one of two categories: small scale or large scale, for

example, GPS tracked pollution levels at a 5 metre resolution or crime data for London councils.

• So why not create an application that can automatically create a Google Maps website from a shapefile and that allows the user to control the number of tiles by limiting either the zoom level or the geographical area?

GMapCreator

• GMapCreator: demonstration of OAC website creation

• OAC-London: ..\data\DUG-examples\OAC\oac-super.html

– 179MB (439MB) 98,018 files

• OAC-East Midlands: ..\data\DUG-examples\OAC\oac-super-EM.html

– 7.61MB (16MB) 2,689 files

• Some buildings: ..\data\MapTube\LC_TQ1268_height_data_product_v1.html

MapTube - Sharing Data

• Allow users to upload their shapefiles and let us host their data, but users can still use the tool to create and host their own data – the best of both worlds?

• By holding the data on our server in a raw format, we have the potential for combining datasets. This might raise some legal issues.

• If the service becomes popular we are going to need a bigger server.

Hardware

The Internet

Upload shapefile from GMapCreator

application

HTTP-POST

A process on the upload server is triggered to pre-create all the tiles needed

for this map

Tile images are copied to the web server

Rich Web Pages

• Javascript, Java and HTML – styling MapTube with components

• Google Web Toolkit• Point-based data and clustering – ‘ononesite’ and eSociety• GPS Tracking and GPX• Linking 2D and 3D• Fade data in and out

Point Data

• The clustering algorithm must be representative

• The pin limit causes problems when panning

• Live Demo: http://localhost:8080/googlemaps/esociety2.html

Weather Data: Synoptic Data

• Weather data is shown drawn around a station circle

• Wind direction is indicated by the arrow and speed by the number of fleches

• Symbols on the left show weather conditions e.g. rain

• Pressure, temperature and dewpoint are also displayed

Fading Data

• Problem: the data completely obscures the map, or is hard to understand if transparent

• Fade the data, or the map?

• Alpha channel in png

Live demo: ..\..\share\opacitytestcensus\erg_OA_2001_ks01ks02ks15_percentage_WGS84.html

Linking Google Maps and Google Earth

• Google Earth is an ActiveX object

• A web page can open Google Earth and control it through a COM interface in javascript

• Follow a GPS track around Virtual London

Live Demo: ..\..\share\Tracking3D\GPXViewer3D.html

Pollution Tracking

A cyclist with a GPS and carbon monoxide sensor was tracked cycling around Bristol. The data is published on the web as an animated track using Google Maps. Live demo: http://www.casa.ucl.ac.uk/bbc/dontdieyoung/log_25-09-2006_154206.html

Conclusion