Building a Standards Based Collaborative GIS

Ian Turton1 and James Macgill2

1Centre for Computational Geography, University of Leeds, UK i.turton@geog.leeds.ac.uk

2GeoVISTA Center, Department of Geography, Penn State, PA USA, jmacgill@psu.edu

Introduction

• Collaboration• Open Standards• System design

Why Collaborate?

• Collaboration is a vital part of many mapping projects

• Maps often form the center piece of discussion and can be used to inform and improve a debate.

• Teams from different agencies cooperating– Emergency response– Disaster relief management

• Longer term project planning– Public participation

Types of Collaboration

• Synchronous Same Place Collaboration– Every one uses same the map at the same

time

• Asynchronous Same Place Collaboration– Every one uses the same map but at

different times

• Synchronous Different Place Collaboration– Map is shared in space when everyone is

present

• Asynchronous Different Place Collaboration– Map is shared in space and time

Synchronous Same Place Collaboration

• Simplest – All clustered around one monitor

shouting “left a bit, right a bit...click there, no there!”

– Can get boring very quickly!

• More complex– Shared desktop/maps on multiple

machines in one room

• Most Complex– Shared display (e.g. Large wall

display) participants can add data etc to main display allowing group interaction

Asynchronous Same Place Collaboration

• This allows a group of users to share data and ideas using a map when some or all are present at different times.

• Equivalent to being able to write on the map or leaving post-it notes on the map to pass on thoughts.

Synchronous Different Place Collaboration

• All users present at same time but distributed spatially.

• This allows users to have a shared map experience on their own desktop.

• Individuals can show data and annotations to other users, data passed as features to allow local styling to be applied.

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Asynchronous Different Place Collaboration

• Users are in different places and are present at different times– Time zone differences– Collaboration over a

long period

• Need ability to annotate the map in a persistent manner.

• Ability to save state in a useful manner, while allowing local styling.

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Open Standards

• Availability– Open Standards are available for all to

read and implement.

• Maximize End-User Choice– Open Standards create a fair,

competitive market for implementations of the standard. They do not lock the customer in to a particular vendor or group.

Open Mapping Standards

• WMS, WFS, WCS etc: These are discussed at length in the literature and will only be briefly described in this paper.

• SLD: The ability to pass out a predefined style to all participants (GeoVISTA Studio) or to allow participants in different countries to view map in their preferred style (e.g. Geologists)

• Annotation (XIMA): Allows participants to draw attention to interesting parts of the map.

Web Map Servers (WMS)

• A WMS client passes an HTTP request to the server– Required layers and styling– Bounding box and CRS– Size and format of image required

• A WMS passes a picture of a map to the client

• Client can also request information about features at a point on the map

+ Security of data, simple client- limited interactivity

Web Feature Servers (WFS)

• A WFS client sends an HTTP request to a WFS– Features required (including filters)– Output format (often GML)

• The server sends the result set • The client is responsible for styling and

rendering the features returned.+ faster rendering and queries, styling

determined by client- More complex client, potentially large

data downloads, client holds data

Styled Layer Description (SLD)

• An XML based language which describes how features are to be rendered.

• Developed to allow WMS clients to choose from a selection of named styles when requesting a map.

• Modern WMS allow the user to upload SLD or refer to a remote style repository.

• This allows two users to view the same features but styled to local standards

Differential Styling

Xml IMage Annotation (XIMA)

• Allows users to draw points, lines and polygons on to an image (WMS maps are images).

• User can attach text, images, video, urls to the geometry.

• The xima representation can be stored on a server and passed to other users.

• A xima aware client can allow users to access the content of the annotations.

Annotated Map

System Requirements I

• Synchronous Meetings– Publish maps to others in meeting– Highlight features of interest in own

and other’s data.– Use data from local stores as well as

remote sites– Communicate to other participants– Ability to save or publish outcome

System Requirements II

• Asynchronous meetings– As before and– Persistence of maps and comments

to allow participants to see previous discussion

Putting it together synchronously

Remote Data

Local Data Local Data

Internet

Publish maps andcomments

Publish maps andcomments

Receive mapsand comments

Receive mapsand comments

Putting it together asynchronously

Remote Data

Local Data Local Data

Internet

Publish maps andcomments

Publish maps andcomments

Receive mapsand comments

Receive mapsand comments

Remote store

The client/server

Map Client

Map server

User interface

Communications

GeoServerMapservIonicCubewerx

GeoToolsDeegreeOpenMapMapbender

IMSVOIPEmail

PublishReceive

Transport Protocol

• Http + Already used by tools– Server configuration needed– Client would need to use unprivileged port (8080) – Firewalls!!!

• Peer to Peer+ Run out of the box– Untested with current tools– Firewalls!!!!

• Grid computing+ Take advantage of virtual organisations– More complex technology

Conclusions

• It is possible to build a system that allows synchronous and asynchronous collaboration between people separated in space.

• By using open standards it is possible to construct most of the system using off the shelf tools.