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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
When the user selects a specific room, information is displayed
in a separate web page. This page can be either an html or SVG
file.
3.1 Data structure and file sizes
As mentioned earlier the, transformation of dwg files to SVG
format was achieved with the use of CAD2SVGmodule. The
source dwg file contains lines, dashed lines, polylines, hatches
and polygons. Due to the fact that these structures are not
identical in SVG, the converter uses mainly the «path» element
represent features’ geometry. SVG provides the general
<path> element, which when used can create a huge variety of
graphical objects.
This general transformation of the various data constructs to one
repeating used <path> element causes the output SVG file size
to be five times larger than the one of the source. This can
become really a problem in a web environment and for this
reason SVGz compression is applied resulting to a zipped file
50% smaller than the original dwg.
4. APPLICATION PROGRAMMING AND
IMPLEMENTATION
In this section, apart from the original application screenshots,
there are explanations about the implementation of several hot
spots in SVG coded images.
At step B the user selects the floor layer he wants to virtually
visit, from a screen that shows the exterior of the building, by
pointing on the desirable level, which is actually an SVG image
(Figure 2). SVG images can be embedded in html pages using
either html <embed> or <object> element as shown in the code
above.
<embed src="NestedSVG.svg"
type="image/svg+xml">
width="500" height="400"
<object data="file://c:/ NestedSVG.svg"
height="400" type="image/sve+xml">
width="500"
Figure 2: Raster building image with SVG rectangle elements
designed for the floor selection.
The picture that the user gets at step C is a ground plan of the
selected floor in SVG graphic format. This image can be
zoomed in and out, panned using the popup menu of the Adobe
viewer by right clicking inside the SVG image. While moving
the mouse cursor over the rooms of the building, some areas
such as rooms, public areas etc. are highlighted (figure 3).
149
Figure 3: Plan of the selected floor where highlighted room is
user's selection
By left clicking on a highlighted feature a new web page is
loaded showing information about the selected area (Figure 4).
Highlighting can be easily implemented using the “set” element
from the SVG specification combined with *mouseover" and
"mouseout" options or by java scripting.
<set begin="r42_1.mouseover" end="r42_1.mouseout"
attributeName="fill" to="#CCCCFF"/>
SVG linking capabilities give the option this page to be rather
an html page (Figure 3) or an SVG one.
Code «a xlink:href-"Testpage2.html" opens an html page.
Code <a xlink:href="Testpage1.svg"> opens an svg page.
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Room Number A.42
Room Usage Office
Telephone Number| +30-210-772 2730
LP. address 147.102.107.200
Name Lysandros Tsoulos
Identity Assistant Professor
Email lysandro@central,ntua.gr
Homepage http://www.survey.ntua.gr/lysandro
|
Photo
Figure 4: information shown after clicking on a ground’s plan
room in html web format.
SVG has the advantage of presenting text information in user's
system language. For example, in case the web page that
appears after users’ selection on a highlighted area is in SVG
format and if the proper SVG code is used, all descriptive
information about rooms will be shown in Greek or English
characters. This can be of course implemented in every
language that can be part of the SVG code.
The following slice of SVG code shows that if user’s system
language is English the “Telephone Number” text will appear in
the SVG web page, or if user’s system language is set to Greek
the "ApiOóc TuAepovov" text will be shown accordingly.
