An Open Source Toolkit for Flexible Browsing of Historical Maps on the Web

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An Open Source Toolkit
for Flexible Browsing of
Historical Maps on the Web
Ohno, Shin
ohnoshin@gmail.com
Ritsumeikan University
Saito, Shinya
Ritsumeikan University
Inaba, Mitsuyuki
Ritsumeikan University
Map browsing on the web is now commonly
used, and most people have used map services
such as Goole Maps, Google Earth, and Yahoo!
Maps. These services also provide developer
API, which makes it easy to integrate map
services into the website. Map browsing in
practical use is covered with those services, but
displaying historical maps as exhibits is not,
which requires different approaches.
We, three members of Web Technology
Research Group of the Digital Humanities
Center of Japanese Arts and Cultures,
Ritsumeikan University have developed an
image viewer, which can handle zooming,
panning, and rotating. Although there exist
many similar toolkits, none has all three features
with JavaScript written. Furthermore, we would
like to share it as open source library.
This paper starts with elucidating Japanese
historical maps, their unique features and needs.
After that, it discusses our image viewer, its
design and implementation to meet their needs.
1. Purpose
Since Japanese historical maps do not have
concepts of geo-coding usually and are
distorted, it is difficult to integrate them with
map services such as Google Maps.
Using Keyhole Markup Language (KML) makes
it possible to integrate these maps with
Google Earth. There is some research on
historical maps on Google Earth (Zeile et al.
2007Nishimura et al. 2007). Although those
tools are highly functional for defining 3D
geographical information on the web, the user
interface is not easy to use for traditional
humanities scholars who are normally not
familiar with KML language. Moreover, setting
the image in Google Earth is not always
their priority. Therefore, when it is necessary
to exhibit original, hand-drawn maps on the
web, one has to take different approaches to
integrating these images into the web.
Because of these issues, image viewers are
usually used to implement historical maps for
exhibition. These viewers enable users to zoom
images, and to see their details if they are
provided in high quality. Moreover, today’s high
technology for user interface allows us to use
such viewers with regular web browsers.
Since most of these viewers are not open
source based applications, however, no room
exists for us to extend and add more features.
Even though they are provided as open source,
most of them depend on a Flash plug-in, and
there is no implementation with JavaScript.
Because JavaScript is lightweight and easy to
be integrated into websites, we have decided to
implement this map viewer with JavaScript, and
open it to the public as an open source product,
and we believe there should be alternative
options for us as open source based toolkits for
these needs.
2. Design
Figure 1: Sample of Japanese historical map

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In this section, we discuss what kinds of features
are required for historical map viewers, and
compare them with related software.
When displaying Japanese historical maps as
image exhibits on the Web, we encounter
difficulties in handling angles. With no clear
concept of top or bottom in these maps, names
of places are labeled from many directions. This
is related to the fact that people in those days
put rather a large map on the table or the floor
to read it. Because of this particular feature of
the historical maps, as opposed to maps today,
browsing tools for these historical maps should
provide a way of viewing them from multiple
angles. Therefore, we decided to design our
tool to support flexible browsing rather than
geographical accuracy.
What we found out about other image viewers
is that many can support zooming and panning,
but not rotating. Most of them also depend on a
Flash plug-in, and there are no implementations
with JavaScript. There are comparisons of
similar software for viewer of maps or images.
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Google Maps/Google Earth
Since their
beginning, these services with web browsers
have become more commonly used, and more
people have become used to them, which
in turn has changed the way we access
geographical resources. However, historical
maps do not have accurate longitude and
latitude, and even using KML to integrate
them into Google Earth, the images are
distorted and we need to change the purpose
to display them. Plus, KML is rather
complicated to maneuver it very well.
API
Free
Rotat-
able
Zoom-
able
Image
Cutting
Open
source
Google
Maps
Yes
Yes
No
Yes
Yes
No
Google
Image
Cutter
No
Yes
No
Yes
Yes
Yes
Google
Earth
Yes
Yes
Yes
Yes
Yes
No
Open
Zoom
No
Yes
No
Yes
Yes
Yes
Open
Layers
Yes
Yes
No
Yes
Yes
Yes
Ojikit
Image
Viewer
No
Yes
Yes
Yes
No
Yes
-
GMap Image Cutter by LCUGMap Image Cutter
by LCU
: To use Google Maps image viewer,
LCU developed GMap Image Cutter tool to
cut a large image into many small pieces.
With this Cutter provided, users can integrate
images to their own website with the same
Google Maps user interface.
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OpenZoom
: OpenZoom is a free and open
source toolkit for delivering high-resolution
images and zoomable user interfaces. Like
GMap Image Cutter, it can cut a large image
into many small file-size images. With this
software, users can download an appropriate
file size to their local computer, which works
to prevent network traffic from congesting
in cases in which the image is too large to
download. This is SWF based, and requires a
Flash Plugin.
-
OpenLayers
: OpenLayers is a free and open
source library for handling geographical
information written in JavaScript. Since
OpenLayers implements both WMS(Web
Map Service) and Web Feature Service, users
can integrate many different maps service
to their own website. It has zooming and
panning features for browsing maps on the
web.
-
Ojikit ImageViewer
Ojikit Image Viewer is the
toolkit we have developed. It has zooming,
panning, rotating features, as well as an open
source license. While it does not have the
function to cut a large image into smaller
files, improvement of broadband allows us
to transfer files without so much reduction.
Moreover, one file is easier to store and
manage than many files.
3. Implementation
Giving consideration to what historical maps
viewers need to be, we have developed an
open source toolkit. This toolkit is written in
JavaScript, and it has lightweight features and
an open source license. Written in JavaScript,
Mozilla and Safari based browser uses SVG,
and the Internet Explorer uses VML to handle
vector images. To develop this library seamlessly
in different browsers, this library depends on
jQuery and Raphael.js.
4. Application
We have applied this tool to Japanese historical
maps as our Center has a large number of