Mobile GIS support for remote sensing data interpretation. - CiteSeerX

Mobile GIS support for remote sensing data interpretation. Karel Charvat1 & Stanislav Holy Co-Author2 1

Lesprojekt sluzby Za ryby, Martinov 197, P.O. Box 21, 277 13 Kostelec nad Labem, Czech Republic Phone: +420 604617327 Fax: +420 81973501 Email: [email protected] 2

Help Service Č Remote Sensing C ernoleska 1600, 256 0, Benes ov u Prahy Phone: +420 301 724620 , Fax: +420 301 724620 Email: [email protected] Presented at ForestSAT Symposium Heriot Watt University, Edinburgh, August 5th-9th of August 2002

ABSTRACT Methods for land use inventory have been already trellised in the past within the frame of many EU projects (MARS, CORINE, FIRS). There are a technology based on an Earth remote sensing method issuing from data purchased in the past. The inventory is based particularly on the use of SPOT, Thematic Mapper (or another RS data) multi-temporary data analysis combined with the use of another spatial data. Basic tool, used for such analysis methods, is the Geographic Information System (GIS). In connection with on line wireless data access, it can bring new quality into interpretation and controlling process. Such systems enable to gather and analyse effectively all available data on the landscape and based on these analyses These are objective of the WirelessInfo project (IST 1999-21056 Wirelessinfo), which offer new possibilities of implementation of mobile communications into remote sensing data interpretation). The whole project is oriented on the connection of GIS platforms with wireless communication (GSM, GPRS). The solution will be based on using open GIS platforms and different sources of communication. Keywords and phrases: mobile GIS, remote sensing, on line data interpretation

1. 0 Mapserver solution The access to the applications shown on the master is realised by a connection through the master computer MapServer. The MapServer was originally developed by the University of Minnesota (UMN) project in cooperation with NASA and the Minnesota Department of Natural Resources (MNDNR). Additional enhancements were made by the MNDNR and the Minnesota Land Management Information Center . Current development is funded by the project, a NASA sponsored project between the UMN and consortium of land management interests. MapServer is an OpenSource development environment for building spatially enabled Internet applications. The software builds upon other popular OpenSource or freeware systems. Mapserver is an OpenSource development environment for building up the spatially enabled Internet applications. The software is built upon other popular OpenSource or freeware systems like Shapelib, FreeType, Proj.4, libTIFF, Perl and others. Mapserver will run where most commercial systems will not or cannot, on Linux/Apache platforms. Mapserver is known to be compile with most UNIXes and will run under Windows NT/98/95.

1.1 Properties: § § § § § § § § § § § § §

Vector formats supported: ESRI shapefiles, simple embedded features, ESRI ArcSDE (alpha release) Raster formats supported (8-bit only): TIFF/GeoTIFF, GIF, PNG, ERDAS, JPEG and EPPL7 Quadtree spatial indexing for shapefiles Fully customisable, template driven output Feature selection by item/value, point, area or another feature TrueType font support Support for tiled raster and vector data (display only) Automatic legend and scale bar building Scale dependent feature drawing and application execution Thematic map building using logical or regular expression based classes Feature labelling including label collision mediation On-the-fly configuration via URLs On-the-fly projection

2.0 Wireless info system architecture The maps are stored on a central computer, which is an Internet and database server of the organisation. For the Wireless communication, the server is connected to a GSM modem 9.6/14.4 kb/s (HSCSD or GPRS). For the parallel data access using fixed connection, the central computer of the organisation is connected to wired network using ISDN modem. The central commuter uses also standard network interface. As tools for data mapping, there is used also a set of standard commercial GIS products (GeoMedia, ArcView, Orbis, Topol). The data access for the users is realised by a Internet viewer which is based on the application Mapserver + PHP + Java Applet + DHTML. The Internet user is limited using Mapserver in the editing of predefined map layers. For clients, working with more simple equipment like HANDHELD ( Ipaq H360s Windows CE / Pocket PC), there is implemented an universal and more simple application of Mapserver for Internet viewer supported by HTML. For clients exist the possibility, to do simple edition of the point and data base data.

Mapserver

WIRELESSINFO

SERVER CGI query

MAPSERVER CGI script

DATA

HTML templates

New data

Data entry PHP / Mapscript

CLIENT WIRELESS COMMUNICATION

MapServer solution

GIF,HTML

CLIENT (HTML/CSS /JavaScript) Java applet

Coordinats and GPS attributs (DDE)

GPS data processing module NMEA 0183 format

GPS

2.1 Implemented Mapserver applications In WirelessInfo, was implemented three different levels of applications. They are: § BASIC application - based on DHTML / java script § ENLARGED application 尨 based on DHTML / java script and java applet. This level of applications supported data collection and connection of GPS § PDA application 尨 based on pure HTML §

2.2 Outputs format For mobile applications is very important the output format from the server. There are three important aspects, which is necessary to take into consideration: § It is necessary transmit minimal amount of the data § It is necessary transmit maximal amount of information § It is necessary use such format, which will be supported by common browsers Original Mapserver applications in the Wirelessinfo project used to work only with GIF format. The GIF advantage is easier development of the client applications (base on the Java-applet).The GIF disadvantage is based on the great costs for the essential licenses by CompuServe (the GIF compression is licensed). That“s why we tried to assure the two others format JPEG and PNG. The PNG main disadvantage is that it is not widespread enough and the Java development is more complicated. The noticeable is the script size, downloaded by application initiation into client computer. These problems are marked only with Java-applet use, on palm OS this problem is not observed. The main advantage of the PNG format is in the small amount of data, comparing to GIF format (less than 10%), and in its zero license costs (encoding+ compression). Currently the PNG format is being used to all ours PDA applications and another special applications using Java-applet. The main disadvantage of the JPEG format is in its maps composition loss compression, containing vector data or rasters in 1-4 colour depth per pixel. Paradoxically by maps compositions containing just the vector data and binary rasters the amount of the output file distinctively larger (and so the data transferred server-client) than the PNG or GIF format The oppositely situation begins when we need to show an aerial or satellite images. Then is the JPEG format outputted from the map server the most advantageous according to size of the file (several times smaller than GIF or PNG format. Moreover the JPEG compression does not takes effect talking about aerial and satellite images, when the optimal rate of compression is set, these rasters are suitable for the web browsers. For the data transfer optimizing in the WirelessInfo applications is running in time of testing (according to the information mentioned above) of the following systems: PNG is implicit output data format § If GIS multicolor raster layers are initiated (containing aerial and satellite images) then the output of the map server is switched to JPEG format with optimal rate of compression. § This solution optimizes (minimize) the amount of transferred data and it has significant financial effect for the map applications using wireless solutions. § The result is possible to use for more complicated applications, which are using Java-scripts, or it can be use for more simple map applications based on HTML+PHP

2.3 Mapserver applications 尨 another possibilities of data access security In the last period until November 2001, were in the WirelessInfo project solution used applications, which assure the follow multiclient model of data access. § Any user, logged to the main page of the map applications, can access and use only data according to his user rights provided by the network administrator. § Name and passwords form of all users are saved in the format out of the WWW tree server and PHP scripts do their verification. Since December 2001 is available new modification of the previous solution, which assure a higher data access security of all WirelessInfo map projects as follow: § Every user could have various data access of the map application layers according to his data access rights. With this mechanism is possible to publish some of maps or data of the focused application. It was impossible in the previous solution. Now the unregistered user can edit just for him reserved layers from every application. Next layers with protected information are available only for the registered user. § Every login and user passwords are saved now into proper file in the encrypted form. § All graphic data are saved out of the www server tree. § All configuration files of maps application are saved out of the www server tree.

All the settings lead to a possible transfer of the WirelessInfo certain applications from the central computer to Internet environment. This modification brings to network administrator and to users these advantages: § In case the data are placed at the more powerful internet server, connected to the spinal internet network, it enables several times faster data access comparing to situation, when the data are stored at the company“s central computer and the data access is available via mobile users (using GSM, GPRS or HSCSD technology) to the database. § This new solution significantly decreases call fees to all the system users (shorter connect time of user via provider to GSM+GPRS (HSCSD)) § It also decreases the call fees for the map application operator (currently GPRS service is by our operators charged for both ways of the call Č in our case by central computer.

3.0 MOBILE GIS SUPPORT FOR REMOTE SENSING DATA INTERPRETATION Methods for land use inventory have been already trellised in the past within the frame of many EU projects (MARS, CORINE, FIRS). There are technologies based on an Earth remote sensing method issuing from data purchased in the past. The inventory is based particularly on the use of SPOT, Thematic Mapper (or another RS data) multi-temporary data analysis combined with the use of another spatial data. The own system for preparing samples will be based on Mapserver solution with Wireless Internet connection to the Handheld. The interpreter will have a possibility to compare an old data with satellite imagery and orthophotos directly in the terrain and to define samples for interpretation. The architecture will be based on previous experience from WirelessInfo project, but this solution will be modified. The expected architecture will be according following scheme. The new tools in architecture will be: • • •

Internal Application Server External Application server Metadata

Internet server Mapserver CGI script

3.1 Internal application server Internal application server will offer new possibilities analyse data trough Internet on line. Grass systems and special statistic libraries will be implemented. The Internal Application Server is new solution in Wirelessinfo system, which offers full analytical possibilities and decision support (DSS). The analytical functions will be accessible trough CGI script and results of analysis will be displayed trough Mapserver application.

3.2 External application servers

Internal Application servers (DSS)

DATA

Metadata

External applications servers are of line application, which are not connected trough Internet with external users. These technologies were already implemented and are used inside of service companies. Service External companies prepares currently all data Application analysis in Wirelessinfo system and all servers outputs, use external applications. For data ArcView analysis and preparation of application maps is currently use ArcView. Operator analyse PhoTopol incoming data prepare applications maps and this results are stored in Mapserver system. In future is expected, that most from this operations will be provided trough Internet by internal application server. Only specialised tasks as photogrammetric operations will be provided in off line system using external applications..

3.3 Metadata Metadata is "data about data.č The importance of metadata grows with using large client service applications for service companies. There will be stored different data sources inside of system. There will be: • Primary incoming data sources • Derived data in different levels • Out coming data

3.4 Data interpretation • Interpretation of satellite imagery on the base of collected data • Statistical analysis For the process of interpretation, controlling following data sources are expected to be used: • Results of interpretation • Satellite images • Orthophotos The process of controlling can be the divided into following steps: • Localisation of the system in terrain • Displaying of the land cover database • Comparison of interpretation results with the reality • Case the results fit, compare the result • Case the results do not fit, display another layers (changes can occurred since the time of satellite images collection). Comparison and evaluation of situation. Sending of an evaluation protocol to the database.

4.0 NEW TOOLS IN DEVELOPMENT According to intentions of the WirelessInfo project is its technological background based on OGC standards. This approach ensures base conditions for interoperability of used geodata services. Until this date, OGC published several standards for sharing geodata over WWW. To the most developed and also adopted by wide community belongs WMS. The WMS is a Web Map Service (specifically an OGC Web Map Service). A WMS is capable of producing maps drawn into a standard image format (PNG, JPEG, etc). based on a standard set of input parameters. The resulting map can contain "transparent" pixels where there is no information and thus several independently drawn maps can be laid on top of each other to produce an overall map. This is possible even when the maps come from different Web Map Servers. From WirelessInfo point of view is important ability of 1.1.0 WMS servers to establish so called cascade servers. Cascade servers play role of hubs of WMS networks and offer possibility to create gateway for mobile devices, which use different sources of geographic information.

In following illustration is sketch of proposed structure of the WirelessInfo network :

WMS is based on transfer of georeferenced maps i.e. images or eventually drawings, which are generated on request. In some cases exist demand on transfer not maps but geofeatures. This possibility belongs to communication among geodata sources. Such type of the service is covered by another OGC specification WFS Č Web Feature Service. This specification defines formal request over WWW, which returns OGC simple features in GML format. GML is an XML dialect for geographic features

REFERENCES K. Charva t et al., 1998: Precision Agriculture - European Approach. Proceedings of the First International Conference on Geospatial Information in Agriculture and Forestry, Lake Buena Vista, Florida. K. Charva t, P. Gnip, F. Pivnicka, P. Faltejsek Topol Č AgroGIS CONCEPT of GIS FOR PRECISION AGRICULTURE, GIM 9/99 K. Charva t, at al., Concept of GIS for Precision Agriculture, proceedings of conference GIS Brno 98, Charvat at all. WirelessInfo Č Work description for the IST project IST-1999-21056, April 2000 Charvat at all WirelessInfo Č Wireless Communication for Forestry and Agriculture, Agile 2001, Brno Charvat at all. WirelessInfo Technical Implementation Plan, February 2001, Brandys nad Labem Charvat at all. WirelessInfo Marketing study II March 2001 Brandys nad Labem Holy at all WirelessInfo Design of system architecture May 2001 Benesov Holy at all WirelessInfo End user interface 2001 Benesov Stanek K at all, WirelessInfo - D12.1 Design of interface,2002 Brno