Applying of Flash Technology in GIS

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Gościniak I., Łagosz Ł., Pełka-Gościniak J. (2003).
Applying of Flash Technology in GIS.
In: M. Gajos, U. Myga-Piątek (ed.). Geographical Information Systems. Interdisciplinary Aspects.
University of Silesia, Croatian Information Technology Association – GIS Forum, SILGIS Association, Sosnowiec, Zagreb, 165-173.
Geographical Information Systems - Interdisciplinary Aspects
University of Silesia - GIS Forum - SILGIS Association, Sosnowiec - Zagreb 2003
Ireneusz Gościniak, Łukasz Łagosz, Jolanta Pełka-Gościniak
University of Silesia in Katowice, Faculty of Engineering, Poland
Introduction
In present global society, when the number of information increases in
progress of time, the most important seems to be to reach the most indispensable
information. Presently the information can be gained in many ways, e.g. from
reports of proprieties and statistics up to digital satellite pictures and
multimediumistic documents. „Geographic Information Systems” (GIS) allows
gathering of all types of information together, basing on spatial relations. In
opportunity to traditional cartographic products they allow analysing in
simultaneous way some actual, necessary information layers, enabling their
simultaneous presentation on computer screen or in a form of listings.
In Poland GIS functions as category of primary importance. For needs of
central Government offices GIS was divided according to the degree of minuteness
of details of collected information of spatial objects, distinguishing:
- Systems of Geographical Information (SIG) – scale above 1 : 5000,
- Systems Information of Terrain (SIT) – scale below 1 : 5000.
SIT is characterised nor only by precision and minuteness of details of data
belonged to it, but typical for it is also institutional aspect It regards all legal,
political, economical and social dependences connected with system activity. The
organisation aspect is also very important, because it presents dependences
between technical means, information resources and user working in the system.
According to the definition by International Federation of Geodesists „GIS is the
tool to make legal, administrative and economical decisions and the help in
planning and development. It consists in database, including spatial data
concerning defined areas and procedures and techniques to systematic collecting,
actualising and access to these data” [7].
One of GIS systems elements is „digital map” and rather its digital
reflection. This map consists not only of point and objects coordinates, but also of
their properties and connection between them. Till now “digital maps” were
presented only by means of specialistic GIS programs, e.g. MapInfo. In this paper
the conception of internet GIS program is presented.
GIS systems
In Poland among people engaged in Geographic Information Systems (GIS)
there is no univocal definition and meaning of this word. Therefore below are
presented some definition of GIS according to English and American literature:
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-
GIS is the informatics system projected to work with data, which are related to
spatial or geographical coordinates. In other words GIS is base-data system
with the possibility to store spatially related data as well as the series of
functions intended to these data processing [1]
- GIS is the system intended to collect, store, verify, integrate, manipulate,
analyse and visualise data spatially related to the Earth surface [2]
- GIS is the automatized system to collect, store, search, analyse and project
spatial data [3]
- GIS is the system built of the equipment, programs and procedures, projected
to collect, manage, manipulate, analyse, model and visualise data spatially
related to solve complicated planning and organisation problems [4]
From above-mentioned definition results, that they are very similar, but they
indicate the technical side of GIS systems. GIS systems were to a large degree
based on the application of CAD type, systems supporting digital cartography and
systems of database management. D.J. Cowen in one of his papers mentioned
importance of decision support by GIS systems: „system of decision support
connected with interactive processing of spatial data to solve problems” [5].
From cited definitions result three main features of GIS system:
1. GIS renders accessible mechanisms of input, collecting and storing of spatial
data and management of them, it secures their integrity and compactness and
allows their initial verifying.
2. On the base of data collected in the system it is possible to realise specific
analyses basing among others on spatial relations between objects.
3. Results of spatial analyses and operations for base-data programs can be
presented in a description (table form) or graphic form (map, diagram, graphs,
figures), therefore the characteristic feature of GIS is visualisation and offering
spatial information in required form.
Systems of Spatial Information connect knowledge from many disciplines:
informatics, geography, cartography, geodesy, administration, the environment
protection, economy, statistics and many others. The base of GIS systems is digital
map. To objects on the map are added different description databases; one of fields'
records contains information of its location in the space. The core of GIS is the
base of geographical data, often described as digital reflection of map, being the
composition of three series:
- numerical map, on which the record of objects coordinates is stored;
- topology, where the record of spatial relations between geographical objects is
stored;
- attributes, qualitative and quantitative features of particular objects or classes.
Base of geographical data as an integral GIS component is the „series of
numerical data relating to objects of geographical character, univocally and
spatially located together with managing programs, which - together with data -
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allows realising defined, precise, formal model of reality in geographical
expression” [6].
Every system should fulfil five basic functions (relating to spatial data):
1. data input,
2. data transforming,
3. data storing, completing and actualisation (data management),
4. data analysis,
5. gaining of final product.
Dependences between particular functions are presented in fig. 1.
Problem
defining
and data
collecting
Product
Data input
Database
management
Spatial
analysis
of data
Data
visualisation
Data
transformation
Fig. 1 Structure of GIS systems
There is still increasing interest in using of global nets – most of all Internet –
in distribution of geodata and securing distance access to local systems of spatial
information. It is also possible to meet more and more frequently with word
InterGIS, which means the integration of GIS system with Internet.
Conception on INTERNET GIS system
Project of this internet GIS program applies co-operation of WWW server,
such as Apache, PHP scripts, CGI scripts and library of Macromedia Flash to
generate visualisation of processed digital maps. The general scheme of such
project activity is presented in fig. 2.
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Application of client
Application of WWW server
START
login, password
user verification
logging
logging error
cookie, SID
choice of files
to translation
file name
if more files
translation
mif2.dat
names of processed
map files
choice of map
to display
name of map file
generating of
FLASH file
change of map
map generated
(stdout)
new parameters
and ranges of map
zoom+, zoommap service
STOP
Fig. 2 Proposed structure of Internet GIS program
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APACHE is the WWW server, containing set of programs, used on huge
number of servers working under control of UNIX systems (Linux), but accessible
also on other platforms e.g. Windows. Considering the fact that it is free, there are:
easy access to code, easiness of installation and configuration and possibilities to
apply, it became the leader among WWW servers.
Possibilities of Apache allow to use it as a server serving any kind of internet
portals – starting from static WWW pages or more developed portals using
dynamical files generating HTML and finishing at huge base-data systems in a
kind of data wholesale firm.
Module character of Apache (possibility to add different enlargements of
server – also at the stage of its compilation) causes that it is completely graduated
solution, which easily allows adapting server to real needs and tasks. Modules
located in Apache distribution enables among others: starting of scripts written in
different programming languages, verifying of users, using different techniques
and facilities (e.g. cookie, files diaries, operations on catalogues). In following
versions the support for the newest technologies is added and the server efficiency
is improved.
PHP: Hypertext Pre-processor is script language acting at the side of server
and settled in code HTML. Therefore the whole code php is located between code
html, and made on server. It is excellent tool to collect data from forms, to generate
dynamically changing www pages, to operate on cookies and to present and
operate on databases. Additionally PHP has support for other net protocols.
Server Apache is most often usable to test pages WWW, made by itself and
mostly to test scripts CGI (Common Gateway Interface) and PHP, which are often
added to our pages as counters, guests books, programs processing different data
Scripts CGI act at the side of server. They process these messages transferred by
means of HTTP at the usage of Internet web browser. These data are most often
written in forms of HTML and transferred by means of method of POST.
When user opens the main page of project, the script PHP (index.php) with
logging in the project is opened. Logging is based on the checking of login and
password given by user with data written in file hasla.dat (passwords.dat) in the
proper catalogue at the side of server WWW. Satisfactory logging opens the access
to project and sets up new session and cookie for user. User receives unique
number, identifying him, which is also written to cookie up to the closing of the
web browser. Number of session and cookie are very necessary in the further part
of the project, because on the base of them it is permitted user to execute scripts
CGI. If user does not open the session or has not cookie on his computer, then he is
unable to execute script CGI, even through the writing of proper net path into file.
Scripts CGI are such protected, that they do not execute function included in them
till the time when session identifier and cookie will be not in agreement with these
values, which user receives at the moment of proper logging into the project.
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When the stage of logging is properly finished, then the redirection into the
following script PHP (mif2dat.php) takes part. This script is responsible for the
selection of files with extension .mif, i.e. files presenting digital map reflection by
user. Files selection is organised in two ways. The first of possibilities is selection
of files located on the server. User can mark one file from catalogue located on the
server, which is in the field of his interest and then run script CGI (mif2dat.exe),
which will make the translation of file to temporary form, thanks to which the data
presenting takes part. When the user has any file answering the form of digital map
with extension .mif and wants to display it using this project, then he can to choose
the second possibility. He can – by means of script PHP - (send_mif.php) send into
server and then, using the first possibility, process it to the form, from which the
digital reflection of the map will be created.
When the user will make a decision of the choice of the proper file with
digital reflection of the map, then this file should be exposed to translation into the
form of file (.dat). This translation is made by means of script CGI (mif2dat.exe).
The activity of this script can be divided into three important stages: opening of file
with extension .mif, translation of file with extension .mif into the form of file .dat,
closing of both files.
Next step is execution of function to file translation from form .mif to form
.dat. When the translation is properly realised, then the file with extension .dat is
open and the function of writing into file .dat is executed for all information,
necessary to create presentation. Data for the file .dat are not written in the text
way, as in files .mif, but in binary way.
After satisfactory realising of all three parts of program mif2dat and creating
proper for the former display files .dat it is possible to go into the last script
(co2.exe). This script, on the base of information included in files .dat and added to
it library MACROMEDIA FLASH generates reflections of given files .dat. On the
base of this information is generated film clip FLASH, where on its particular
layers the proper reflections of files .dat are included.
Very important and ticklish matter in script co2.exe is calculation of socalled KOD, which is directly connected with algorithm of Cohen-Sutherland. It is
used to designate objects, which have not enough room to be wholly located within
actually browsed window of zooming in of the given map, and more precisely to
mark objects, which not ever point is located within the range of actual window of
zooming in. To be sure, the library Macromedia Flash has algorithms cutting
objects to the range of actual window, but they are not sufficiently good, because it
happens, that at zooming in and next zooming out of mere Flash, these objects go
beyond the area provided to map drawing. Then, we use algorithm by CohenSutherland to calculate, from which side points being beyond the range of window
of zooming in are located.
170
This is the end of programming connected with dynamic creating of Flash
film clips. But there is still problem of proper organising of graphic interface,
which should be perspicuous and intuitive in usage.
Conclusions
This paper is an important link connecting local systems of spatial information
with wide group of Internet receivers, who are interested in geodata applying.
Thanks to Flash technology it is possible to present geodata in simple and clear
way for every user.
Bibliography
1. Star J., Estes J.: Geographic Information Systems: An Introduction. Prentice
Hall, 1990.
2. Handling Geographic Information: The Chorley Report. Department of the
Environment (UK). London 1987.
3. Clarke K.: Analytical and Computer Cartography. Prentice Hall, 1990.
4. Cowen D.J. The National Center for Geographic Information and Analysis.
5. Cowen D.J. GIS versus CAD versus DBMS: what are the differences?
"Photogrametric Engineering and Remote Sensing" 1988 nr 11
6. Miksa K.: SIG a SIT. Materiały na V Konferencję Naukowo-Techniczną PTIP.
Warszawa, 9-10 listopada 1995
7. Piotrowski R.: System Informacji o Terenie - Program Modernizacji.
Warszawa 1991.
8. Tomlinson R.F.: Geographic Information Systems - A New Frontier. "The
Operational Geographer" 1984 nr 5.
9. Michalak J.: OGIS - Integracja systemów informacji geoprzestrzennej
w geologii. INFOBAZY '97.
10. Pavlidis Theo: Grafika i przetwarzanie obrazu. Algorytmy. WN-T . Warszawa
1987.
171
University of Silesia in Katowice, Faculty of Engineering, Poland
S u m m a r y
It seems that in GIS high quality of graphic map presentation is of essential
importance. The lack of it is often noticed in internet graphic applications, because
the majority of maps here presented is made in raster form, what makes zooming in
of high quality impossible and zooming out can cause the lost of information on the
given map. This paper is a proposition to use flash technology in Internet
applications to present maps. It allows presenting maps of high quality of graphics
devoid of above-mentioned faults. This technique applying gives also the
possibility to import maps made in typical GIS tools, as MapInfo etc. Internet GIS
application presented in this paper allows creating the content of looked map in a
dynamical way in dependence of needs and with co-operation of person, who looks
over it. This system allows remote control of processing of data collected of GIS,
creating Internet program GIS. This new quality – interactive map can be also used
in applications developing knowledge of the environment and distance learning
systems, which for geographical programs in the majority of cases require
presentation of thematic layers.
Keywords: spatial information systems, Internet, FLASH technology, interactive
map
Uniwersytet Śląski w Katowicach, Wydział Techniki, Polska
Zastosowanie Technologii Flash w GIS
S t r e s z c z e n i e
W systemach GIS bardzo istotna wydaje się być wysoka jakość prezentacji
graficznych map, a jej brak często odczuwany jest w internetowych aplikacjach
graficznych, gdyż większość prezentowanych tam map jest przedstawiona w
postaci rastrowej, co uniemożliwia wykonanie powiększeń o dobrej jakości a
pomniejszenia mogą powodować utratę informacji na prezentowanej mapie. W
artykule zaproponowano wykorzystanie technologii Flash w aplikacjach
internetowych do prezentacji map o wysokiej jakości grafiki, pozbawionych wyżej
wspomnianych wad. Zastosowanie tej technologii daje również możliwość importu
map opracowanych w typowych narzędziach GIS, takich, jak: MapInfo itp.
Internetowa aplikacja GIS, prezentowana w niniejszym artykule, daje możliwość
172
dynamicznego tworzenia treści przeglądanej mapy w zależności od potrzeb oraz
przy współudziale osoby ją przeglądającej. Taki system pozwala na zdalne
kierowanie przetwarzaniem zgromadzonych danych systemu GIS, tworząc
internetowy program GIS. Ta nowa jakość – mapa interaktywna – może być
również stosowana w aplikacjach rozwijających wiedzę o środowisku i systemach
distance learning, które dla programów geograficznych w większości przypadków
wymagają prezentacji map tematycznych.
Słowa kluczowe: systemy informacji przestrzennej, Internet, technologia FLASH,
mapa interaktywna
173

Applying of Flash Technology in GIS

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