MAPPING FLOOD EXTENTS IN THE FLORIDA EVERGLADES USING XMLL, GOOGLE EARTH, AND ACTIONSCRIPT: AN EXAMPLE OF WEB-BASED COMMUNICATION OF GEOGRAPHIC INFORMATION

jumpthroatSoftware and s/w Development

Jul 4, 2012 (5 years and 2 months ago)

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MAPPING FLOOD EXTENTS IN THE FLORIDA EVERGLADES USING XML,
GOOGLE EARTH, AND ACTIONSCRIPT: AN EXAMPLE OF WEB-BASED
COMMUNICATION OF GEOGRAPHIC INFORMATION

Amy Cohen

Department of Geography and Regional Studies
University of Miami


Abstract

This paper documents the development of an interactive web map designed to
communicate geographic research using three different technologies: the Extensible
Markup Language (XML), the Google Maps API for Flash, and ActionScript 3.0. These
technologies are used in conjunction with geospatial data related to a research study
involving the use of Synthetic Aperture Radar (SAR) in monitoring hydrologic
conditions in the Florida Everglades. The data are incorporated into an interactive web
map using Adobe Flex. The map product allows the user to navigate the study region,
view water depth gauging station locations and details, overlay satellite imagery, and
more. In addition to the development of the map, this paper briefly introduces the three
technologies used, discusses the importance of remote sensing and GIS in wetland
monitoring, and considers the implications of web mapping technologies in the field of
geography.

Keywords: Adobe, Everglades, Flash, Flex, geovisualization, GIS, Google Maps,
hydrology interactive web map, remote sensing, SAR, XML




Introduction
Web-based cartography and geographic information systems (GIS) have
proliferated alongside developments in web application technologies and the integration
of these technologies with GIS. Commonly manifested as navigational tools, weather
maps, and “infotainment”, the interactive web map has become a widespread, familiar
mode of communication for many individuals and organizations with computer and
Internet access. These maps are not only user-friendly but also can be easily developed
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using free open-source mapping application programming interfaces (APIs) made
available on the Internet. This project exemplifies one way in which interactive web
mapping technologies can be used to communicate geographic research to scientists,
professionals, and the general public via the Internet. While geographic research does not
always necessitate the use of cartographic elements, that which involves geospatial
analysis can greatly benefit from Internet maps as a medium. Web-based cartography and
GIS expedites the communication of geographic research and facilitates circulation of
geographic ideas to a broad audience, improving the visibility of the discipline while
encouraging interaction and peer review. Much like GIS, these technologies
accommodate the systematized organization and display of geographic data, as several
layers of information can be viewed on the same base map. Presenting geographic data in
this manner allows the viewer to examine the data at her own pace and to view more
information than may be possible or practical to include in an academic paper. This is not
to suggest that interactive web mapping could replace traditional methods of research
communication, but that it acts as a useful, intuitive complement to these traditional
methods. Moreover, much has been written about web-based mapping and, particularly,
web-based GIS as a possible solution for those left out of the GIS movement, “those
without support for machinery and infrastructure and training and also those for whom
GIS needed to be a social, communal, and local collaboration tool more than a hard
scientific instrument (Miller, 2006).”
This project applies web technologies to the organization and visualization of
geographic research involving the use of GIS and remote sensing data in monitoring the
hydrology of the Florida Everglades. Three of these technologies are discussed in this
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paper: XML, Google Maps API for Flash, and ActionScript (Adobe Flash/Flex). The first
section of this paper discusses the use of GIS and remote sensing in environmental
management (specifically the Florida Everglades) and provides an example of how GIS,
remote sensing, and web technologies can be integrated to represent geospatial data. The
second section considers the utility of web mapping in the field of geography and the
potential contributions that geography can make toward harnessing web technologies to
communicate research goals and findings. Basic elements of the different technologies
and how they can and have been applied in a geographic context are included in the
appendix. The objectives of this paper are to provide an introduction to some of the
technologies currently being applied to interactive online mapping, to demonstrate their
applicability in geographic research, and to broach the subject of the relevancy of web-
mapping in the field of geography. This paper suggests that interactive web mapping can
be a useful and beneficial complement to geographic research and demonstrates a method
by which others can produce their own interactive web maps.

Remote Sensing, GIS, and Web Mapping in Environmental Management
Interactive web maps can be implemented toward a variety of practical
applications, such as finding directions [Link 1], researching regional crime reports [Link
2], and measuring “walkability” [Link 3]. Furthermore, the medium of interactive web
map can be very effective, impressive, and engaging. Current iterations of Internet web
maps range from the resourceful to the informational to the entertaining, and beyond (the
experimental perhaps?). It should be noted, however, that interactive web mapping
technologies were developed, for the most part, outside of the academic sphere for
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commercial purposes. This does not in any way mean that such technologies are not
applicable within academia. On the contrary, recent growth and distribution of web-based
GIS and mapping technologies has stimulated the use of these technologies in areas of
geographic research, such as conservation planning (Harris and Hazen, 2006). Taking this
into consideration, the interactive web map medium has tremendous potential to
contribute to such efforts as environmental awareness and management.
The content that follows provides one example of an application of remote
sensing, GIS, and web mapping technologies that integrates environmentally pertinent
research with the appealing qualities of interactive web maps for effective
communication. The first subsection that follows briefly discusses a study conducted on
the use of SAR data in monitoring hydrologic changes in the Florida Everglades, the
results of which are to be organized and displayed using web mapping technologies. The
second subsection describes the steps taken to translate these results to a web application
that facilitates display of and interaction with data pertaining to the study.

Mapping Flood Extents in the Florida Everglades
The application of GIS, remote sensing data and related technologies toward
environmental planning and management efforts is widespread in professional and
governmental contexts as well as in the academic fields of geography, ecology,
anthropology, and biology, to name a few. A major site of environmental planning and
management in the United States is the Florida Everglades. Florida’s prized subtropical
wetland ecosystem is currently the subject of large-scale management efforts at the
Federal and State levels. One important component of these management plans involves
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protecting and preserving water resources in South Florida. In order for water resources
to be protected and preserved, it is necessary to monitor quantitative changes in water in
the region. Hydrologic monitoring, and the further step of creating prediction models,
requires accurate and up-to-date knowledge of flooding throughout the ecosystem on a
regular basis. This is currently being carried out by the Everglades Depth Estimation
Network (EDEN), which utilizes a system of gauging stations interspersed throughout the
Everglades to measure and interpolate changing water depths, thus creating a time series
of water depth surfaces that can be integrated with other research interests as well as
prediction models using GIS. Daily and hourly water data are publicly distributed online
[Link 4].
Current research on hydrologic modeling in the Everglades focuses on creating
more accurate surfaces and models while cutting monitoring costs through the use of
remote sensing data, such as space-based Synthetic Aperture Radar (SAR), to regularly
determine and map flood extents (Ramsey, 1995; Augusteijn and Warrender, 1998;
Baghdadi et al., 2001; Kandus et al., 2001; Rosenqvist et al., 2002; Kasischke et al.,
2003; Taft et al., 2003; Li and Chen, 2005; Papa et al., 2006; Wdowinski et al., 2004;
Wdowinski et al., 2008). The research visualized via the interactive web map produced
for this study is centered on research findings involving the use of three different SAR
platforms (ERS, Radarsat, and JERS) in monitoring the hydrology of the Everglades
(Figure 1). The study focuses in particular on the applicability of the standard deviation
of backscatter values, which represent the strength of the signal returned to the radar
sensor, in wetland mapping and monitoring. It reveals that the standard deviation of radar
backscatter within a given window size is affected by changing hydrologic conditions,
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that the three different SAR platforms are conducive to specific types of wetland
analyses, and that SAR backscatter responses to hydrologic conditions are vegetation
specific. Using remote sensing and other geospatial data, the Everglades study
contributes to the body of work aimed at advancing the use of these technologies in
wetland monitoring applications (Cohen, 2009). The web-mapping project described in
this paper uses content related to this study to illustrate how geospatial research can be
displayed using remote sensing, GIS and web technologies to facilitate communication
with other researchers, professionals working in Everglades management, and the general
public.


Figure 1. A screen shot of the interactive map product displaying the study region, a
Radarsat SAR image, and several ground station locations.

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Representing Geospatial Data Using Web Mapping Technologies
The three web technologies discussed in this paper (XML, Google Maps API, and
ActionScript) in addition to the SAR images, GIS data, and research results related to the
Everglades study were incorporated using the Adobe Flex software package to create an
interactive web map. This included the following steps:

1. Acquire a Google Maps user key from Google.com. This key is necessary in order
to publish and distribute the final mapping product.
2. Download the Google Maps API for Flash software development kit (SDK). This
kit includes the components necessary to implement the Google Maps interface in
a Flash environment.
3. Import the Google Maps API for Flash SDK to Adobe Flex and create a new map
component.
4. Produce an XML file to organize spatial data. When viewed in a web browser,
information contained within this file will be retrieved by the Flash Player
runtime according to ActionScript code stored within the SWF. Examples of such
information include the latitude and longitude coordinates of ground station
locations and positioning information and URLs necessary to display raster
overlays of SAR data.
5. Construct a set of menus and controls in Adobe Flex that will constitute the map’s
user interface, allowing the user to toggle markers, information windows, and
imagery, as well as to access external images and graphs.
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6. Program how these menus and controls will react to user input. For example,
when the box next to a ground station name is checked, that station’s location will
be displayed on the map. When unchecked, it will be removed. When the point
being displayed is clicked by the user, a window will open containing information
on that particular ground station (Figure 2). This information, including the spatial
coordinates, is retrieved from the previously mentioned XML file.
7. Export the final product from Adobe Flex to an SWF, which can then be imported
to an HTML file and uploaded to a server for distribution on the Internet.

The final map product displays relevant geospatial data used in the Everglades study
on the Google Maps platform. Since the study deals primarily with physical surface
features, the foundational map is set to the “Satellite” view, as opposed to the “Map”
view, which displays map elements as vectors, such as boundary lines and major
highways. When opened, the map is automatically centered on the Everglades study
region in South Florida. The ground stations utilized in the study are displayed, and can
be easily toggled off or on using a series of checkboxes included in the “Stations” menu
of the web page. SAR imagery can be viewed by toggling the check boxes in the
“Images” menu. Links to legends, figures, and results are included and open in new
windows when selected. Finally, research-related documents are made available for
download.
The final map product was designed to provide users with some background on SAR
and the Everglades, to visually explore the landscape of the region via Google Map’s
satellite overlays, and to examine data sources, methods, and results pertinent to the
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study. Because the user has control over the visibility of several different map overlays
and figures, more information about the project can be included overall than would be
practical for an academic paper. A collapsible “accordion” style menu aids in organizing
the information available, as well as a slider that gives the user control over how much
window space is taken up by the map within the browser. All of the map elements
pertaining to the project are accessible from the interactive map website so that the user
does not have to navigate to another URL to view pertinent information. Although users
completely unfamiliar with GIS and remote sensing technologies might find some
difficulty understanding the content of the Everglades research study, it is hoped that the
interactive map’s user friendliness and the accompanying documents and links describing
these technologies will provide at least a starting point for those interested in learning
more about the subject.
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Figure 2. A screen shot of the interactive map product displaying the information box for
a selected gauging station in the Florida Everglades.

Future Prospects
The interactive map created as part of this project facilitates the display and
navigation of geospatial data related to a specific body of research. While
geovisualization is considered a useful tool in itself, interactive web maps have the
potential to include more complex and analytical tools, such as those accommodated by
desktop GIS applications. For example, the Google Maps API for Flash includes a
predefined set of services for geocoding addresses and providing driving directions.
Although these tools in particular are not relevant within the scope of the Everglades
study, they help to illustrate possible applications that could be offered through
interactive web maps. Other feasible and useful tools could include measurement tools,
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digitization, network analysis, data classification, and search functions. Allowing users to
input their own data and export personalized map applications could expand the
applicability of interactive web mapping to users with little or no GIS experience. The
main limiting factor in terms of user interactivity is processing speed and storage
capacity. In this sense, desktop GIS applications are much more conducive to multi-tiered
projects that involve complicated data analyses and large data sets. Recent studies show
potential for improving speed and efficiency in distributing large rasters, such as
remotely sensed images, using web mapping applications (Zhao et al., 2005). Likewise,
digital libraries and new methods of managing geospatial data are emerging as the
interconnectedness of geospatial information on the web expands and new technologies
designed for compatibility with geospatial data are developed and distributed
(MacEachren, 1998). Nonetheless, while web-based maps are proliferating, web-based
GIS is still in its infancy.

Interactive Web-Mapping and Geography
Effective visualization of geographic information plays an important role in
efforts that utilize and depend on maps to achieve compelling and convincing
communication of geographic research. Visual communication of geographic ideas in
particular often plays an integral role in decision-making contexts, from urban planning
to environmental activism and beyond. For example, in their research on the use of
realism in geographic visualization, Appleton and Lovett (2003) note that increasing the
amount of detail in landscape depictions using 3-D GIS technologies helps viewers relate
to the geographic information being presented. Although it certainly cannot justify a
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weak intellectual foundation, their study shows that visual presentation of geographic
information, especially in a policy context, is strengthened by visual elements that
reinforce the accuracy and importance of the data. Interactive web maps that utilize
satellite imagery and support 3-D visualization are advantageous in terms of realism and
interface familiarity, as well as quick and easy access. In addition, the user has the ability
to view various layers of geographic information overlaid across a single backdrop, to
control scale and navigation, and to assess the data at her own pace. These qualities of
ease of use and high-caliber visualization of geospatial data, referred to by Jeremy
Crampton (2008) in his article Cartography: maps 2.0 as a “new spatial media”, can
enhance the communication, visibility, and tangibility of geographic research. Moreover,
interactive web mapping and GIS encourages participation, constructive criticism, and
peer review, as many users not only have access to the maps themselves but also to the
knowledge and tools necessary to create them.
Another benefit of the web-based map as a communication tool involves the role
of geographic visualization in news media. Geographic information, for a wealth of
applications, is frequently communicated in news media via visualization, often in the
form of informational maps. With news media, and even some academic journals,
increasingly becoming web-based, web mapping as a geographic communication tool has
great potential in regards to publishing and news making (MacEachren, 1998).
Geography as an academic discipline has a long and winded history, having gone
through many changes since its inception in terms of overall focus, methods embraced,
methods shunned, and its perceived usefulness in society (Johnston and Sidaway, 2004).
The argument that interactive web mapping improves the practicability and visibility of
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geographic research could be seen as a return to “an instrumentalist strategy to try and
reposition and enhance geography as a discipline”, as discussed by Kitchin and Sidaway
(2006) in their commentary on geography’s strategies featured in the Professional
Geographer. While this emphasis on web mapping, a close relative of cartography, runs
the risk of reinforcing the increasingly prevalent impression of geography as a State
and/or commercial tool, it could just as easily serve to underline the usefulness of web-
based geovisualization in helping to relay intellectual endeavors that emerge from the
field of geography that may have been obscured by the current emphasis in the field on
geotechnologies.
Geography is a multi-faceted discipline the practicality of which extends far
beyond mapping, although it is frequently subject to vague questions of relevance and
validity. Web maps can potentially work toward current interests in the discipline,
communicating research and illuminating geographic concepts in the realms of
development studies, environmental change detection, and resource management, to
name a few. Furthermore, the ability of both GIS-users and non-GIS users to develop
web maps and create spatial content engenders a GIS movement beyond points, lines, and
polygons to new forms of spatial representation. That said, the conduciveness of web-
based mapping and GIS in general to non-Euclidean, context- and culture-specific
representations of space is, at this point in time, more theoretical than practicable (Miller,
2006).
The use of the Internet as a medium for communicating geographic research has
many advantages; however, the disadvantages inherent in the medium should not go
unmentioned. The Internet has the benefit of reaching a broader audience than may be
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accessed via other media, whether it is an audience composed of policymakers,
academics, prospective students, or the general online community. Unfortunately, a line
can be drawn between those who have Internet and computer access and those who do
not, resulting in a “digital divide”, a phenomenon that has been linked to income as well
as race (Chakraborty and Bosman, 2005). This divide has been not only discussed but
challenged in the field of geography. Nonconventional GIS such as interactive web maps
that extend GIS beyond the realm of proprietary geospatial tools and expensive software
packages have been viewed as an “attempt to bring the notoriously nebulous and
contradictory idea of accessible-but-powerful, technological-but-democratic,
professional-but affordable GIS into some focus (Miller, 2006).” However, the
distribution of Internet access remains unbalanced, and many ideas revolving around the
use of web-based mapping and GIS toward positive social change never leave the journal
pages. It should also be mentioned that the nature of web-based media lacks the
permanency and robustness implied by academic journals, which could also work against
its effectiveness. On the other hand, perhaps the transience of web maps and their
disconnection from traditional academic and professional cartographic methods and
techniques will foster the reexamination of maps as objective and neutral products of
science and elucidate the values and judgments of the developers (Kitchin and Dodge,
2007). Considering the values and judgments of the institutions that provide the backdrop
for the creation of web maps, for example those of the megalithic Google Incorporated, is
a complex issue that is highly discussed in geographic literature; however this subject is
beyond the scope of this paper.
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This project demonstrates that GIS users and developers have direct access to a
number of technologies that make creating interactive web maps not only possible but
also rather straightforward. Crampton (2008) attributes the availability of such
technologies to the “free and open source software” (FOSS) philosophy of what he refers
to as the “geoweb”. The web-mapping example provided here benefits from the FOSS
philosophy that made this work possible and supports the potential of interactive web
maps, academically, professionally, civically, and recreationally. In addition, all of the
tools necessary to create a similar map are introduced, facilitating replicability. Although
web mapping and GIS endeavors have the auspice of evolving GIS beyond the
traditional, research upon which this particular web map is based is very much defined by
scientific, empirical techniques common to conventional GIS. The objective of this
project was not to discuss the advantages and short fallings of GIS, but to create a
visualization and communication tool that introduces other students and educators to web
mapping technologies in a geographic context and to encourage researchers to explore
these tools in their own endeavors. It is likely that as these technologies advance, web-
based mapping and GIS will become capable of supporting higher degrees of user
interaction, more intricate functions, and faster response times, hopefully for the better.










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Appendix


Web-Application Technologies
XML
The Extensible Markup Language (XML), developed by the World Wide Web
Consortium in 1996, is an open technology used to describe data. XML-based markup
languages are supported by most Internet browsers and are commonly used for data
exchange via the Internet (Deitel, 2008). XML-based markup languages are generally
used to structure and contain information, rather than to display it. Information is
enclosed within tags, or keywords associated with the data that act as identifiers and
structural elements. Because there are no predefined tags in XML, it is a powerful
encoding mechanism for all types of structured data, including Web-based geospatial
information (Lehto and Sarjakoski, 2005). XML vocabularies are specialized XML-based
markup languages. Many different vocabularies of XML exist for a variety of fields and
applications. XML vocabularies defined specifically for geospatial data include the
Geography Markup Language (GML), developed by the Open GIS Consortium (OGC)
[Link 5] and the Google Corporation’s Keyhole Markup Language (KML) [Link 6].
XML vocabularies specific to geospatial information include elements that represent
spatial objects, usually expressed as points, lines, polygons, and image overlays that
accommodate spatial coordinate information and other descriptors.
The encoding of spatial data using XML has been implemented in a variety of
geographic applications, including mobile map services (Lehto and Sarjakoski, 2005), the
online mapping and sharing of disease information (Gao et al., 2008), and Internet
Geographic Information Systems (GIS) (Chang and Park, 2005). An XML vocabulary
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was created specifically for this project to organize and display geographic content
related to the use of GIS and remote sensing data in monitoring the hydrology of the
Florida Everglades. Tags indicate the specific coordinates and feature attributes of
geographic points, polygons, and ground overlays. The figure below provides a sample of
information contained within the XML file used in this project related to the one of the
ground stations implemented in the Everglades study. The “STATION” element consists
of attributes such as “name” and “shape”, as well as child elements (elements one tier
lower in the XML hierarchy than that of the “parent” element) such as the station
coordinates, indicated by the “LATITUDE” and “LONGITUDE” tags.

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Figure 3. An example of a “STATION” element within an XML document.

The hierarchical method of data organization facilitated by XML allows elements
to be nested within other elements. This makes retrieving information related to each
station simply a matter of calling the name of the station element followed by the
embedded child element pertaining to that particular parent using dot notation. For
example, the latitude of the station named “3AS3W1” can be accessed through the syntax
‘STATION.@3AS3W1.LATITUDE’, with the @ symbol indicating that 3AS3W1 is an
attribute of the STATION element. Storing geospatial information using an XML
<STATION name="3AS3W1" shape="point" horizontal_da
tum="NAD83" vertical_datum="
NAVD88" UTM_zone="17N" units="feet">

<LATITUDE>25.8575
</LATITUDE>

<LONGITUDE>-80.770833
</LONGITUDE>

<LOCATION_AREA>Water Conservation Area 3A
</LOCATION_AREA>

<VERTICAL_CONVERSION from="NGVD29" to="NAVD88"
method="CORPSCON 6.0 with modified CERP grid, 2005" value="-1.5">
</VERTICAL_CONVERSION>

<STATION_TYPE>Freshwater
</STATION_TYPE>

<MAJOR_VEGETATION>Ridge or sawgrass and emergent marsh
</MAJOR_VEGETATION>

<MAJOR_AVERAGE_GROUND_ELEVATION>7.48
</MAJOR_AVERAGE_GROUND_ELEVATION>

<MAJOR_COLLECTION_AGENCY>USGS
</MAJOR_COLLECTION_AGENCY>

</STATION>

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structure also allows for the data to be organized and stored separately from the
application, thus simplifying the process of modifying and appending new information to
the existing XML document. In addition, XML schemas can be established to specify
structural rules that must be met for specific vocabularies. Schemas are in essence XML
documents themselves, and can be used to validate other XML documents. Validation of
an XML document according to a particular schema ensures that the document conforms
to the schema’s specifications (Deitel, 2008). Since the XML document created as part of
this project is implemented by only one application, no schema was created or applied.
However, creating an XML schema specific to a particular purpose allows for the
standardization and broader applicability of XML documents to larger projects.

Google Maps Flash API
Virtual globes have been gaining in popularity as high-resolution satellite and
aerial photography has become more accessible and in some cases, free. The budding
public interest in geospatial technologies has spurred ongoing new developments in the
realm of online web mapping and geovisualization. Google Maps and Google Earth are
just two of many virtual globe programs that allow users to view and create geo-tagged
content, or content endowed with spatial coordinates. Geo-tagged content can range from
place marks indicating places of interest to three-dimensional diagrams of buildings and
beyond.
The Google Maps Flash Application Programming Interface (API) allows Adobe
Flex and Flash developers to embed the Google Maps browser within Flash applications.
APIs accommodate the use of external services and databases by other software programs
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and applications. In the case of this project, the Google Maps Flash API allows Google
Maps data, functionality, and interfacing to be accessed, modified, and displayed using
Flex components, which are constructed using the programming language ActionScript.
Using the Google Maps Flash API, developers have the ability to create dynamic,
interactive maps that expand the basic capabilities of Google Maps and provide an
adaptive platform from which more personalized, content-specific maps can be created
and distributed on the Internet. Pre-defined map objects provided by the Google Maps
API, such as points, information windows, and navigational buttons, can be integrated
into the Adobe Flex and Flash environments to support the display of and interaction with
geospatial data. In addition, the developer can create custom map components that suite
the purpose of her project. Although Adobe products are close-source (and on top of that,
pricey), Adobe Flex can be downloaded and licensed for free by students and educators
[Link 7]. The Google Maps API is open-source and free for download for all Internet
users [Link 8].

ActionScript
Adobe Flash and Adobe Flex CS4 (Creative Suite 4) are commercial multimedia
platforms that can be used to create dynamic, interactive movies and applications. Flash
and Flex applications are programmed using a proprietary scripting language known as
“ActionScript 3.0”, a language similar to JavaScript (Deitel, 2008). In this project,
ActionScript is implemented through the Adobe Flex environment, converted to
ActionScript bytecode, and wrapped in a binary container called a Shockwave Flash file
(SWF). This process is known as “exporting” or “publishing”. Flash movies and
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applications are usually viewed through web browsers using Flash Player, a Flash client
runtime environment, as in the case of this project; however they can also take the form
of stand-alone programs, supported by the Adobe AIR runtime. Flash client runtime
environments such as Flash Player, Adobe Air, and Flash Lite (specifically designed for
mobile devices) are accessible for Windows, Macintosh, and Linux systems. These
ActionScript-based programs are considered to be portable programs because they are
implemented by a Flash runtime that is compatible with a variety of systems and devices,
as opposed to being limited to one particular operating system or hardware device
(Moock, 2007). In addition to being portable, Flash Player is free [Link 9] and ubiquitous
(Figure 4). It is estimated that Flash Player is installed on 99% of Internet-enabled
desktop computers in the US, Canada, UK, France, Germany, and Japan (Millward
Brown, 2008).


Figure 4. Ubiquity of Flash Player as estimated by a Millward Brown survey, conducted
December 2008. Image courtesy Adobe.

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The Google Maps API for Flash facilitates the use of ActionScript to create
interactive, dynamic map content that can be viewed both online using Flash Player and
offline using Adobe Air. This project in particular incorporates an SWF containing
interactive map content embedded within an HTML website. User control of map scale,
navigation, and viewable content is programmed using fundamental ActionScript 3.0
elements specific to the Adobe Flash and Flex software programs in conjunction with
ActionScript objects and methods provided by the Google Maps API. These include
mouse event responses such as the ability to “drag” the map in any direction, information
windows that are displayed when the user clicks on a point marker, ground overlays such
as satellite images and other raster data, map control interface objects such as zoom bars,
and formatting styles that allow for custom visual presentation of map elements. The
figure below presents an example of ActionScript code used to establish map properties
such as the scroll wheel zoom, which allows the user to “zoom” toward and away from
the map features (or to increase and decrease the scale of the map) using the scroll button
included on some mouse controls. In addition, an “Event Listener” is created in order to
retrieve and display the coordinates of the mouse pointer over the map. These coordinates
are displayed at the top left of the interactive map product associated with this project.

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Figure 5. An example of ActionScript code used to initialize the Google Maps user
interface.











private

function

onMapReady(event:Event):
void

{


var topRight:ControlPosition =
new ControlPosition(ControlPosition.ANCHOR_TOP_RIGHT, 16, 16);

var topRight2:ControlPosition =
new ControlPosition(ControlPosition.ANCHOR_TOP_RIGHT, 36, 100);

var myZoomControl:ZoomControl =
new ZoomControl(new ZoomControlOptions({position: topRight2}));

var myPositionControl:PositionControl =
new PositionControl(new PositionControlOptions({position: topRight}));

map.enableScrollWheelZoom();

map.enableContinuousZoom();

map.setCenter(new LatLng(26,-80.8), 8, MapType.SATELLITE_MAP_TYPE);

map.addControl(myZoomControl);

map.addControl(myPositionControl);

map.addControl(new OverviewMapControl());

map.addControl(new ScaleControl());

map.addEventListener(MapMouseEvent.MOUSE_MOVE, showLatLng);

}

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References

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Augusteijn, M.F., and C.E. Warrender. 1998. Wetland classification using optical and
radar data and neural network classification. International Journal of Remote Sensing 19:
1545-1560.

Baghdadi, N., M. Bernier, R. Gauthier and I. Neeson. 2001. Evaluation of C-band SAR
for wetlands mapping. International Journal of Remote Sensing 22: 71-88.

Chakroborty, J. and M. M. Bosman. 2005. Measuring the digital divide in the United
States: race, income, and personal computer ownership. The Professional Geographer 57:
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Links

1. http://maps.google.com/

2. http://www.spotcrime.com/fl/miami

3. http://www.walkscore.com/

4. http://sofia.usgs.gov/eden/

5. http://www.opengeospatial.org/

6. http://code.google.com/apis/kml/

7. http://www.adobe.com/products/flex/buy/

8. http://code.google.com/apis/maps/documentation/flash/

9. http://get.adobe.com/flashplayer/