Interactive Web GIS Using MapObjects and IMS

ABSTRACT

We have developed a Web GIS using MapObjects and MO-IMS, which has the following functions;

• Search features with attribute values
• Set map display properties
• Create tables and graphs
• Pathfinding
• Link to a web site from a selected feature
• Data (features and attributes) input on a browser

We have built some client applications with an ActiveX Control or a Java Applet that we have developed.

We would like to introduce its functions and report some of the problems we have faced during its development.

1. Purpose of Development

We have aimed at developing an interactive GIS on the net, which is distinct from those Web applications that only support simple search and display of a map. The main purpose has been to develop an Intranet GIS for business use. We have made a great effort to enable data input on our Web GIS because it seems especially important for a Web GIS in Intranet environment of business to be interactive.

We have set our goals to the development of a server application with GIS functions for use in web environment, and client controls for utilizing this server application. We have succeeded in developing controls (ActiveX Control and Java Applet) that facilitate the development of a client application with GIS functions.

What we intend to introduce in this paper is some examples of Web GIS application that we have developed with these controls. We call our system "Pasco Web GIS".

2. Web GIS Development Tools

We have built client applications with an ActiveX Control or a Java Applet. The former has been developed mainly for Intranet, and the latter for Web GIS in Internet environment.

The tools and technologies that we have used in the development are as follows.

(1) Map Server

We aimed at developing general-purpose server functions independent of client application functions. The Web server was developed with MapObjects1.2 and MO-IMS 1.0/2.0 using Visual Basic 5(SP3)/6(SP2). It supports ShapeFile, SDE data, BMP file and TIFF file.

(2) Web GIS Client Applications

• Client Application with ActiveX:

  We developed an ActiveX Control for the development of a GIS application on the net. We named this control "Pasco GIS View Control".

  With this control, we developed two kinds of client application as examples. They use ActiveX Layout Control or Dynamic HTML and ActiveX Document. The application with ActiveX Document uses socket because there was a serious problem with Esrimap.dll. We have used Visual Basic 5(SP3)/6(SP2) and VBScript for the development of these applications.

  
  Figure1 Data Flow of Client Application Examples (ActiveX Control)

• Client Application with Java Applet:

  We developed a Java Applet using JBuilder 1.0. We developed the basic portion of this as Java Beans. We have built an example application with this applet.

  We have also separated this Applet into multiple Applets with unique functions. You can combine these Applets quite freely to develop a client application. For instance, we have built another example application with four of these separated Applets. One basic Applet, which we call "Pasco GIS View Applet", and each of other three Applets inter-communicate to provide the client application with a variety of functions.

3. Client Application Examples

The client controls that we have developed have a great number of functions. We believe that these functions can provide many of GIS capabilities that have never been realized in web environment. We will describe the examples of client applications developed with these controls. These examples use only a part of their full capabilities.

Functions

• Select areas and layers to display
• Select a field for each layer to show symbols and annotations (labels)
• Use spot symbols to show proportional data from feature attributes (Use graduated symbols of the same shape to represent the quantitative data, and simultaneously use segmented wedges to display several categories of data)
• Select features by clicking on the map and selecting a point or forming a line or a polygon
• Zoom in, zoom out, pan, full extent view

GIS Operations

• Search features by selecting a layer and a field and specifying the attribute
• View an attribute table for a specified feature and calculate values
• Create a pie chart or a bar graph for the selected features
• Measure distance or calculate area
• Draw concentric circles around a selected point
• Pathfinding
• Calculate (total) attribute values for features selected by buffering (line/polygon)
• Link to a web site or a linked photograph from a selected feature
• View and overlay aerial photographs and satellite images
• Copy a map, an attribute table, or a graph on the screen to the clipboard

Data Input

An authorized client can enter, edit and save data (point, line or polygon) as well as attribute values. You can also assign a symbol for a point data. For instance, you may enter attribute information such as feature name and URL with some of the application examples. We developed this function because we thought that data input would be an essential function in business applications.

Figure 3 is a sample client application with ActiveX Layout Control.

4. Performance Test Results of Client Application Examples

We have tested the performances of example applications on different browsers and operating systems.

Although Java Applet has been known to work independent of browsers and operating systems, we have found that it practically depends on both of them, probably because of the differences in implemented Java Virtual Machines. In our case, this problem was serious when Proxy server was in use as shown in Table 1. In that case, the applications with Java Applet did not perform properly except on Internet Explorer 4 and 5.

5. Development of Map Server Functions

In developing the Web GIS map server functions, we have tried hard not to make it specialized with limited use in specific fields. We have provided the server with some typical functions, which you can combine to realize sophisticated GIS capabilities. With our map server, you can make settings that conform to most of the functions of MapObjects.

As already described above, when you want to customize a client application, you would only need to build or modify a client application using our ActiveX Control or Java Applet. Our map server is not supposed to be customized.

Map Server Settings and Functions

• Extract prefecture/city codes and city boundaries from data
• Set display properties for each layer (name and order, show/hide; display scale of layer and label; data entry permit)
• Set display properties for each field (name, unit; show / hide; calculate total)
• Set field groups (to display attribute and create pie charts and graphs)
• Set map display properties (as MapObjects' ValueMapRenderer and ClassBreaksRenderer settings)
• Set labels and symbols (as LabelRenderer settings)
• Set icons (images) for a point data
• Set pathfinding conditions (costs and parameters)
• View and check display settings
• User management

6.Technical Constraints

(1) Problems with MO-IMS

We have faced some serious technical constraints during the development of Web GIS. MO-IMS2.0 and MapObjects2.0 have not dealt with some of these problems.

a) Esrimap.dll

• Esrimap.dll does not handle data (request query) over 1024 bytes. The excess data would be lost.

  We have avoided Esrimap.dll by using socket in addition to HTTP. The use of socket solved this problem, but we needed to develop functions such as map server assignment and queue processing in order to fulfill the important functions of Esrimap.dll. Instead of developing such functions, we have decided to develop an alternative to Esrimap.dll.

b) Weblink Control

• A problem with Weblink Control causes the map server to go down when data from a single field exceeds 256 bytes.

(2) Problems with MapObjects 1.2

• A pie chart is not created if data includes value 0 or null.

• Image quality deteriorates to 256 colors when we use MapObjects to make a BMP (bitmap) file. Consequently, the quality of GIF file made from this BMP with Weblink Control becomes poor, too.

  Instead of using MapObjects, we used Visual Basic and succeeded in making a full-color BMP file without quality deterioration. We have converted this BMP file into GIF file with Newton Corp�fs ImageKit.

• MapObjects does not seem to process Unicode. Because of this problem, only single byte characters can be displayed correctly. For example, we could not display Japanese fonts properly along a line such as street or railroad with MapObjects1.2.

  We have added a subroutine (dll) to display such characters (Japanese fonts) without using MapObjects. We have heard that MapObjects2.0 should take care of this problem.

7.Technical Challenges for Future Web GIS

There are some technical challenges for future Web GIS that we must deal with.

We realized that communication session management and exclusive control are the major difficulties in Web GIS development compared to the development of client/server GIS.

We intend to develop the following functions in order to make our Web GIS more useful in a variety of business.

• Relation with outside databases:
  Intranet GIS in business requires this function to keep up with daily updated information.
• An improved Esrimap.dll or its alternative:
  We need this function to enable the transmission of data over 1024 bytes. This would be especially important in real estate related systems, for instance, in which considerable amount of data might be entered and stored.
• Complicated data retrieval (conditional search) function:
  Complicated data retrieval function is desirable for business such as real estate information management.
• Symbol settings by a Web GIS client:
  We would like to realize this function on Web GIS with image data transmission (our current Web GIS) as on Internet GIS with vector data transmission. This function may be useful in area marketing and specialized studies.
• Snapping function in data entry:
  This function is important in Web GIS for facility management. For instance, you might want to use this function to connect the sewer lines at their nodes.

We have already realized the first two functions, and we are currently trying to develop the rest.

8. Pasco Web GIS Demo-Site

We have set a demonstration site for our Web GIS on the Internet. You can try an example of a client application developed with our ActiveX Control (Pasco GIS View Control) using Dynamic HTML. It is in English and Japanese. Our demonstration site is at http://ims.pasco.co.jp/EN.

ACKNOWLEDGMENTS

We would like to thank the following engineers for their contribution:

• Katsuyuki Waki
  
• Yasushi Koyama
  

AUTHOR INFORMATION

Yuka Hirano
Office of GIS Technology Development
Pasco Corporation
1-1-2 Higashiyama
Meguro-ku, Tokyo 153-0043
Japan
Telephone: +81-3-3715-1661
Fax: +81-3-3715-1990
E-mail: Yuka_Hirano@sed.pasco.co.jp

Kazuo Hirota
Acting General Manager
Office of GIS Technology Development
Pasco Corporation
E-mail: Kazuo_Hirota@sed.pasco.co.jp