TimeMap Open Source Consortium

Map Viewers

We have developed a robust TimeMap viewer application (TMWin) which will display both local and internet-accessible datasets together in a time-enabled map window. The viewer uses time-based filtering to display time slices on demand and will generate simple map animations as AVI files. We have also developed a powerful Java map viewer for Internet-accessible datasets. The Java map viewer may be embedded in any web page and supports on-the-fly temporal queries. Both TimeMap viewers are key enabling technologies for the Electronic Cultural Atlas Initiative.

Windows Map Viewer: TMWin

TMWin is a Windows application written using Borland Delphi and the ESRI MapObjects GIS component. In addition to normal mapping functionality, such as zooming, panning, labelling and symbolisation of map layers, the TMView has specialised temporal mapping functionality.

Functionality
Time-enabled GIS: TMWin creates map layers on the fly by applying an SQL filter to vector datasets (stored locally as ESRI shapefiles), allowing the map to be updated as the time limits are changed. A time bar beneath the map - which can be zoomed in to individual days, months or years, or out to the full time range of the datasets displayed - allows the user to set the time limits by dragging the ends of the current time range shown by the grey bar. on methods of handling time. The TMWin Interface Map Animation: The TimeMap methodology allows for explicit recording of 'snapshots' as vector GIS objects, and of 'transitions' as attribute data attached to them. TMWin uses this principle to generate map animations, which can be output as .avi (movie) files, to illustrate the passing of time. Access Internet Datasets/ Distributed GIS: TMView can search and access remote datasets through a metadata clearinghouse developed for the Electronic Cultural Atlas Initiative (ECAI) and can integrate both local and remote datasets together in a time-enabled map window. Inset showing dragable timebar Map-object to resource linking: One of the essential functions of TMWin is the linking of objects on a time-filtered map to local or web-based resources – such as web pages, photographs, multimedia or other maps. Map-object to resource linking is the key to spatial and temporal browsing of large datasets, such as heritage inventories, and a key component of our strategy in developing museum-based visitor access to historical data. TMWin was used to build a museum kiosk - Sydney TimeMap - at the Museum of Sydney in November 2000. It has also been employed in public information kiosks for the Parramatta Historical and Archaeological Landscape Management Study.

Key Components
Clearinghouse Browser: TMWin includes a map-based metadata clearinghouse browser which allows: connection to remote datasets filtering of the clearinghouse based on spatial and temporal limits and metadata searches display of bounding boxes for datasets on a map of the world display of metadata for selected datasets, including extended HTML-based documentation display of thumbnail and detail views of datasets. Remote datasets are filtered on the server, the subset is downloaded and cached locally, allowing for offline access and the responsiveness of a local application rather than Internet data transfers. Visual cues to layer display range MapSpace Manager: TMWin has a MapSpace Manager window which supports the design and saving of multi-layer maps as MapSpace files (analogous to ArcView projects or MapInfo Workspaces). MapSpaces define the datasets to be used (including non-local datasets accessible via the ECAI metadata clearinghouse), the SQL filters to be applied to create map layers, the symbology to be applied for each layer, and spatial and temporal limits. Layer configuration dialogue Layer control: TMWin handles both time and layer display scaling. In TMWin, layers can be set to display both within particular scale ranges and within particular date ranges using simple visual metaphors. Visual metaphors are also used in the legend of the map window to indicate which layers lie outside of the current display range. A clock symbol indicates that the layer lies outside the current time range for the map, a plus magnifying glass indicates one must zoom in to see the layer, and a minus magnifying glass that one must zoom out. When a greyed-out layer is highlighted in the legend, its spatial extent is flashed on the map and its temporal extent is flashed on the time bar.

Java map viewer

While much of our work has gone into development of the Windows map viewer and data preparation toolkit, it became clear that the download and installation of a complex Windows application was a significant hurdle for the average user simply wishing to retrieve data in a web browser. This led us to develop a Java mapping applet which may be embedded in any web page.

Functionality

The TimeMap Java map viewer is an intelligent client which downloads vector and raster data and can handle temporal filtering, data-driven hotlinks and access to distributed heterogeneous datasets indexed in a central metadata clearinghouse.

In addition, because the TimeMap Java viewer downloads data rather than dumb images, it can handle immediate zooming and panning, time filtering, switching layers on/off and popup information on map rollovers. This contrasts with the approach of downloading an image generated on a server and returning to the server for each pan, zoom or enquiry. The intelligent client approach makes for a much more responsive application once the initial download has been completed.

Embedding the Java map viewer in your web pages

The applet can be embedded into web pages with a few lines of Javascript, providing an immediate interactive mapping capability without installation of any complex or expensive software on your web server. Embedded maps can draw on the increasing number of free-access datasets registered in the ECAI Metadata Clearinghouse. These include worldwide background maps as well as more local datasets. The applet may either be pasted into a web page - in which case it will display a set of datasets specified by their ID numbers in the ECAI metadata clearinghouse - or it can be called to display the results of an online clearinghouse search such as that illustrated below.

Organisations can add datasets to the clearinghouse, and to their embedded maps, through an open web interface. Suitable shapefiles, GIF or JPG files already on your web site can be added to the clearinghouse in a matter of a few minutes and become immediately mappable. SQL server databases with locational information (e.g. latitude and longitude columns) can also be easily added to embedded maps. Access to the data can be password controlled.

Hot link to other data

Hot links on the map can be built through a simple metadata specification which allow the applet to link from objects on the map to different pages in a complex web site (for example to pages generated from a database e.g. for a heritage sites register or photographic catalogue).

Custom solutions

Individual solutions for organisations which wish to maintain their own data for interactive mapping, rather than drawing on the ECAI Metadata Clearinghouse, can be built rapidly thanks to a drop-in XML metadata clearinghouse file and CGI scripts which can be easily installed on most servers. The only support technology required is standard, off-the-shelf tools downloadable free from the Internet. For further information, please contact the TimeMap development team. The Showcase-Applications page features several customised examples of the Java Viewer in action.

Data formats

The applet currently supports data ranging from simple zipped shapefiles, GIF and JPG images on a web server to data servers such as the MrSID image server, a number of SQL data servers (MySQL, Interbase and Sybase for example). General Open GIS Consortium Web Map Server and Web Feature Server compatibility should be available soon.

Parameter settings on the applet allow specification of the following:

For the applet as a whole:

Source of applet and data
Size of applet window
Initial and maximum spatial extent (latitude/longitude)
Initial and maximum temporal extent
Background colours
Components of the interface to show/hide
Tool buttons to show/hide
Automatic layer ordering on/off

By layer:

Layer title
Initial visibility
Temporal display range
Spatial display range
Incremental loading on zoom, pan and time change
Rendering (size, colour, symbols)
Access passwords

Requirements

The applet is approximately 500K in size with necessary libraries and will run within the standard VM in Internet Explorer 4 and above on PC, Unix and Mac. For Netscape 4 and above, Java VM 1.3 is required (free download from Sun for PC & Unix, not available for Mac).