Java Mobile and Space Mapping Service (WMS) application integration

1 Introduction

More than 80% of human's daily life behavior is related to spatial position, and it has the innate need for spatial position information acquisition. With the development of society, the scope of people's activities is more and more large, and more and more uncertain. This kind of mobility and uncertainty brings the market and challenge to mobile communication, and it brings unlimited business opportunities for the development and expansion of space location service. Space Location Service (Lbs--location Based Services hereinafter referred to as LBS), refers to the use of mobile communication network, wireless location, combined with GIS geographic information system, to provide users with location based navigation, query a value-added service. lbs belongs to one of the typical applications in mobile GIS, which involves geographic information service, computer application interoperability, wireless communication, mobile phone and other technologies, which belongs to the interdisciplinary academic field of spatial information and computer network collaborative computing. At present, the most widely used wireless communication technology consumer groups are mobile users, these users have a greater demand for space location services.

At the same time, with the development of computer network and wireless communication technology, the application of Java mobile phone has been emerging in China. Java Phone (note: J2ME mobile phone refers to the support of Java Micro EDITION,MIDP mobile phones, usually we call "Java mobile phone" is "J2ME mobile phone") a change of traditional mobile phone function fixed, system closed mode, For Java phone developers and users with an open interface, application developers and users can be based on their own needs to develop or download the software in accordance with their own. At present, J2ME (Java 2 platform,micro Edition) has become one of the most popular mobile phone application development platform. The development of the Java handset has provided the conditions for developing the Space Location Service (LBS) based on the Java mobile platform. According to the demand of mobile phone users for Space location service, the author developed "Personal Navigation system" based on Java mobile phone. Earlier versions of the system (based on Motorola 388 mobile phones), the June 2002 China Software Association, Motorola, Sun Company and other joint "national Wireless Java Application Contest" won the award for excellence.

Generally speaking, it is difficult to develop LBS and GIS navigation system on a Java mobile phone with low CPU speed, limited memory and storage space, and some lbs users get access to navigation map information, which is often realized through the integration of Java mobile phone and related LBS business Application Network Service application. One of the core technologies of any LBS system is the access and operation of the Java mobile phone to the network GIS image navigation resources. In the independent development of the "personal navigation system", the use of J2ME mobile phone (Motorola388, Motorola A760, etc.) through the GPRS network, J2ME mobile phone and Space WMS (WEB Map Service) Service Application integration, and access to navigation map, and complete the relevant operations. The following is an introduction to J2ME mobile phone's access to network image resources.

2 The acquisition of image object by J2ME mobile phone

Acquisition and display of image by 2.1 J2ME mobile phone

The MIDP 1.0 Standard version of the J2ME handset only supports images in PNG format. You can display both static and non-static images. A static image is an image that, once created, does not change the content of the image. Rather than a static image is that an image can be dynamically created with J2ME drawing statements. Because of the limited computing power of J2ME mobile phone, the author uses the raster image of static PNG format in Mobile GIS based on J2ME Mobile. J2ME mobile phone for the creation of static images there are two main ways: the first way: directly by the bundle in the application JAR file to load and create a static image [1]. The method is constructed by:

Image img=image.createimage (String pngname);

Where: Pngname is the image file name in the J2ME application jar file. Because the J2ME cell phone has limited storage capacity (usually hundreds of k or a few megabytes), the spatial data volume of lbs and mobile GIS is relatively large, it is difficult to meet the storage of mobile GIS spatial data simply by storing the data of lbs and mobile GIS clients in the mobile client local J2ME mobile phone in this way. , it is also difficult to update the data of mobile clients.

The second way: Create a static image using binary PNG format data.

Image Img=image.createimage (byte[], int offset, int length);

Where: byte[] is an array of data in PNG format, and Offset,length is the offset and length of the array used respectively.

This is a flexible way to create static images, and the PNG format data array can come from anywhere in the J2ME program (such as: Network). The author develops the LBS, mobile GIS system based on Motorola388 mobile phone, which uses mobile client's Motorola388 mobile phone to dynamically read the GIS spatial data of the network server (of course the data format can be vector or raster format), and it can easily update the client's data.

2.2 GIS image dynamic production of Space map Service (WEB map Services)

Spatial Web Services is a research area of interoperability between spatial information applications. With the development of computer hardware and software technology, space Web services are developing very quickly, and the corresponding standardization work is also rapidly unfolding. Space information currently OGC has been developed or proposed by the main space Web services are:

Web Map Service,

Web Registry Service,

Web Feature Service,

Web Coverage Service,

Styled Layer descriptor for WMS,

Geocoder Service,

Transaction WFS and so on,

Among them: Iso/tc211 has adopted a space web-related standard: The Web Map Service (ISO 19128) standard, and the ISO 19136-geography Markup Language (Geographic Information Markup Language GML).

Figure 1: Space Web Service Architecture