Indexing and delivery of
We invited Ian Johnson to describe an innovative research tool for clients using map collections in the National Library and elsewhere Location and time as index Libraries face an increasing challenge in indexing a variety of resources, including maps, photographs, sound files, video and born-digital material. This is particularly the case for national institutions with broad-ranging mandates, such as the National Library of Australia. Traditional retrieval, which relies on shelf order, authorship, subject keywords and free-text search of catalogue information, can become unwieldy for large collections of repetitive material, such as map series or photographic collections. Effective searching relies on consistent application of the indexing system by both the cataloguer and searcher. In some cases, for example the National Library’s collection of over 500 000 aerial photographs, it would be impossible to provide a distinct classification for each image because date, authorship and so forth are identical for large series of images, and there is no title or textual content. Spatial location and time offer a viable alternative which is applicable to a great deal of library material, not just maps and aerial photographs. Artistic and literary works are generated at a particular time and place; novels often reference real places; reference books and research papers often apply to a particular region or reflect knowledge in a region at a particular time; photographs, audio and video generally record a specific place and time; while maps, atlases and travel books are inherently geographic. The South Seas project <http://southseas.nla.gov.au/> uses maps of Cook’s Endeavour voyage as an index into daily accounts, providing a perfect example of spatial and temporal indexing of written material, and linking from maps to digitised resources.
Although we may struggle with street directories, we have an inherent understanding of spatial location and time, since we have to negotiate them in the course of our daily lives. They therefore provide a highly intuitive way of indexing and finding information. Unlike words—whose meanings are wide open to personal interpretation, even within a single culture—spatial location and time can be defined unambiguously. Even though people use different local map grids and calendars, these systems can generally be converted to latitude, longitude and Universal Time Coordinates. Spatial location and time are also exhaustive, because there is a coordinate for every point on earth throughout its existence. Spatial and temporal indexing are thus well-suited for intuitive searching of collections such as PictureAustralia (www.pictureaustralia.org) or the National Library’s rare map collection. Spatial location and time can be used to index events either through a single latitude, longitude, time point (for a single well-defined event, such as the birth of a modern author) or through recording a spatial ‘footprint’ and a time range within which an event occurred, or is thought to have occurred (for more complex or less precisely recorded events, such as a military campaign or a historical photograph). Spatial and temporal search Using these principles, and with the support of grants from the Australian Research Council, Macquarie Library P/L, the David Ramsey Map Collection and the Electronic Cultural Atlas Initiative (ECAI), the University of Sydney TimeMap project <www.timemap.net> has developed a Web-based search interface which can be adapted to different library applications and forms the core technology for the Electronic Cultural Atlas Initiative <www.ecai.org.> The search uses an interactive world map to define a spatial extent and time range (Figure 1) and retrieves any map resources which fall within or overlap this envelope. Maps are indexed through a spatial footprint (red rectangles on Figure 1) and a time range. The search area is defined by dragging a box on the interactive map (blue arrow tool and rectangle) and the time range is selected with the time bar (which also filters the footprints shown on the map). A textual search can also be added. Any spatial search of this type will retrieve a large number of items, because it includes all items which fall within the defined search area (for example, local plans) and all items which include the defined search area (for example, maps of the world). Therefore a method was developed to sort items which most closely match the search area above those that form a very small part of the search area, extend far beyond it or slightly overlap it. Rather than the exclusion method of textual search, which risks missing significant resources, our spatial search rates the most likely resources at the top.
The search interface and mapping system can be applied to any type of resources identified by spatial footprints and date ranges, including paintings, photographs, sound and video recordings as well as maps. As such, it is quite suitable for the wide range of collections managed by an organisation such as the National Library. It has been applied it to diverse data, ranging from theatrical performances recorded in AusStage <www.ausstage.edu.au>, to archaeological projects, heritage sites and historical images—indeed anything that has a location and date range is a prime candidate for indexing and display by spatial location and time. Although libraries have rarely embraced this form of indexing, it can just as well be applied to books and other written material, if location and date information is recorded in the catalogue. ECAI associates at the University of California Berkeley are even trying to automate the extraction of spatial information from placenames in text to provide spatial search and mapping of live news feeds. Indexing historical images The Sydney TimeMap kiosk, installed at the Museum of Sydney in 2000, used TimeMap interactive maps to index historical images (drawings, paintings and photographs) of Sydney in relation to contemporary historical maps (Figure 2 left). Many of the images were derived from the Picture Australia database hosted at the National Library, while others came from the archives of the City of Sydney and the New South Wales State Archives. The map and time bar allowed visitors to zoom to an area, display symbols representing the location and the direction view of images dating to the selected time range, and click on the symbols to display the corresponding image on a second screen (Figure 2 right). Maps as images Maps present unique challenges and opportunities to the conventional library. This is reflected at the National Library, as in many libraries, by the existence of a distinct map collection. Maps actually represent the geographic space they occupy, rather than simply referring to it; they are widely variant in physical format; maps bound together in a single book often need to be indexed separately, owing to their differential spatial coverage or subject matter (e.g. the variety of maps in most historical atlases which cover different areas of the world, different time periods and different thematic content); and, when digitised, maps can be as large as 2 gigabytes, making them hard to deliver over the Web.
The National Library has a program to digitise its map collection <www.nla.gov.au/digicoll/#maps> and make it available online using the MrSID image server to deliver Web resolution images that can be progressively zoomed to reveal detail. A similar approach has been adopted by the David Rumsey Map Library <www.davidrumsey.com>, the largest private map collection in the USA (150 000 maps), which also uses the MrSID image server and contributes its metadata to the Over the last few months, the TimeMap project has been recording geographic coordinates for Rumsey’s current set of 9000 online images, allowing them to be located through the ECAI search interface (Figure 1). For half these images, the bounding box recorded is simply a means of spatially locating the image, as the digitised material includes atlas covers, tables of contents and pictures. However, where the image is a map, it is possible to go much further and use the coordinates to scale the image, position it geographically and overlay it with other maps and modern geographic data in the TimeMap viewer (Figure 3). The TimeMap project has also indexed a number of maps from the NLA’s digitised collection, allowing them to be mapped and overlaid with other data.. Delivering maps on the Web The core of many of the projects described in this article is the TimeMap TMJava mapping application, which provides interactive access to distributed map data indexed in the ECAI Data Clearinghouse, including a small number of maps from the National Library and the majority of David Rumsey’s digitised map collection. TMJava is a flexible interactive map viewer weighing in at around 350 kilobytes (one-time download) which runs in any standard Web browser. TMJava provides a much greater level of interactivity and enquiry than static jpg map images or maps delivered through a MrSID image viewer. TMJava can request and overlay data interactively from distributed map resources, and thus load increasing levels of detail (where available) as the map is zoomed from a world view to a single city block or historic site. Map layers can be turned on and off, and objects on the map can be selected, searched and hyperlinked directly to database records. TMJava can also generate simple jpg map images for low bandwidth connections, with limited zoom, pan, layer control and hyperlinking through JavaScript.
On-demand generation of time-based map animations on the Web has also been pioneered for the presentation of historical information for teaching, museums, visitor centres and general interest. Map animations can also be used to present live contemporary data such as traffic flows or network faults (two recent unanticipated applications). The TMJava time bar has controls to step the interactive map through time or play the map in a time loop. The applet then writes a URL which generates the animation as a Macromedia Flash format (.swf) file for embedding in a website. Where data is frequently updated, the animation can be generated live on demand simply by calling the URL. Flash has great advantages for Web delivery due to its compactness: the Korea TimeMap animation (Figure 4: see the Animations page of the TimeMap website) is a high resolution animation lasting 10 minutes, yet the file is only 1 megabyte and is easily viewed on a modem connection. The Flash format is also interactive, allowing movies to be paused, rewound, fast forwarded and hyperlinked. Participatory systems In order to facilitate spatial indexing for future projects, an interactive location digitiser, which can be embedded in a Web page, has been developed (Figure 5). As the map is zoomed, it automatically loads more detailed maps, down to individual heritage site plans and city streets (where the data is available). The digitiser can automatically insert the coordinates of points, rectangles and other shapes into database fields, or data can be copied to the clipboard for pasting to other programs. This digitising tool is part of a broader project to develop methods for collecting information from communities through the Web. The TimeMap team has been working with the Centre for Cultural Research, University of Western Sydney, to develop a pilot cultural atlas of western Sydney into which communities can enter their own information, including photographs and scanned images, personal accounts, events and so forth. The tool will be used to index a substantial collection of photographs from Angkor in Cambodia and make them available to the ARC Linkage grant partners. Leveraging the explosion in digital cameras, it is hoped that the help of travellers and residents can be enlisted to contribute photographs of heritage sites and local culture from around the world, in order to build an interactive worldwide heritage map rich with photographs. Finally, there is a plan to release TimeMap Web mapping software and tools as Open Source in the course of 2005. More information is available from the TimeMap website <www.timemap.net>. IAN JOHNSON is Director of the Archaeological Computing Laboratory, in the Spatial Science Innovation Unit at the University of Sydney NSW 2006. He can be contacted at johnson@acl.arts.usyd.edu.au. |
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