ArcIMS tutorial (2)

Chapter 2 use author (Part 1)

 

Chapter overview

This chapter describes how to use author to select the data to be released and how to display the data.

The success of any GIS website depends on the quality of the data used. So the first thing to do is to find the right data source for your website. This chapter will discuss what types of data ArcIMS uses. With the appropriate data source, you need to consider how to arrange the data to your website and display it as needed. These are all tasks that need to be done in author. After the work is completed, author will generate a. Axl file. You will learn how to create the. Axl file, its content and its role in ArcIMS.

In chapter 3, we will learn more about other content processed by author.

 

Author

ArcIMS site creation can be divided into three main applicationsProgramThe first application is author, which allows website developers to determine which data is used and how the data is displayed. Author allows you to change the display of polygon, points, lines, and text labels as required, or set the display scale range so that the elements are displayed only within a certain scale. In addition, you can set variables for the query Attribute Table data, or set precise coordinate points for street-based address encoding.

There are two ways to start author in ArcIMS: opening in the program directly and opening through manager. The two methods are basically similar. The only difference is that author started in manager can create a map service, but author opened in a program cannot. Note that you must define and start the map service before entering the design phase of the website.

The final output in author is the. Axl file. An Axl file is an XML-based text file that saves the selection of map layers and their symbols into an ArcIMS readable file format.

 

 

ArcIMS metaphor: Data

Data is the basic raw material for building a website in ArcIMS. Therefore, there is no ArcIMS without data. The data can be compared to the food and drinks in a restaurant. There are many types of food, such as apples, cucumbers, and breads. Likewise, there are many different types of data, such as image data and shapefiles data.

 

 

Add layers using Directories

Whether you are using author in the program or author in the Manager, you must use the directory to add a data layer to your website. The add layers tool button on the toolbar opens the Directory window.

The Directory window is similar to the resource manager in windows. You can first locate the folder where layers are stored, and then use the mouse to highlight the layers you want to add to the website. ArcIMS displays only three types of data in the Directory window: shapefiles of ArcView, layers of SDE, and image files. Press ctrl to select multiple layers at the same time. After selecting the layers to be added, click Add layers in the Directory window to add these layers to the TOC of author.

If layer data is only stored in a few folders and you do not want to search for the data in the Directory window every time, you can add them as "favorites ". This is similar to bookmarks in Web browsers. Specifically, right-click the folder you want to add in the Directory window and select Add to favorites. This file table will appear in the "favorites" section of the directory tree. Click "ize favorites" in the Directory window to organize your favorite folder. These folders are saved in another. Axl file (favorites. Axl) and can be saved for future use.

 

Shapefiles

The shapefiles file format is a format used by ArcView GIS to store the geometric features and attribute information of geographical elements. The geometric information of elements is stored in the form of a series of vector coordinates.

ArcView generally creates at least three files for each shapefile. The. SHP file stores the geometric information of elements, the. DBF file stores the attribute information of elements, and the. shx file stores the index information of element sets. Sometimes, you can create other index files to accelerate the analysis and query speed.

If you want to learn more about ArcView and shapefiles, refer to the other two courses: ArcView elementary tutorial and ArcView advanced tutorial.

 

 

ArcSDE)

ArcSDE is included in ArcIMS. ArcSDE is essentially a client/server software used in mainstream databases, such as Oracle, microsofr SQL Server, and IBM, which has won DBI, Sybase,, Informix, storage, management, and quick retrieval of spatial data. ArcSDE is highly scalable, making it easy to integrate spatial data with non-spatial data.

ArcSDE can be well integrated with some other client applications of ESRI, such as ArcIMS, ArcInfo and ArcView, and CAD products such as microstation and AutoCAD. It also supports market solutions of third-party developers. SDE ensures that any organization can provide space data and drawing to any user on any server of any network.

ArcSDE allows you to manage large spatial datasets with millions of spatial elements. ArcSDE can be applied to enterprises at all levels, thanks to its collaborative processing between customers and servers. ArcSDE provides open data access over the network through the TCP/IP protocol. At the same time, ArcSDE can run in different operating system environments, such as UNIX and Microsoft Windows clients and servers.

 

 

 

Image Data Format

Image Data is a pixel-based data format. Each pixel or pixel has a value. Common image data includes satellite images, aerial photos, and scan files. In ArcIMS, you can add image data as a layer to ArcIMS. Image data is often displayed as a background.

The server of ArcIMS supports multiple types of image data.

Only three formats of image data-GIF, JPG, and PNG files can be displayed in the client web browser. These images, especially .jpg files, are often called lossy files. Here "lossy" means that although the image compression greatly reduces the file storage space, it also loses some image information. Therefore, these types of image data can be transmitted online faster, but at the cost of reduced resolution.

GIS has a special image format, ArcInfo grid. Grid uses a pixel matrix to represent a certain geographical or phenomenon. You can think of a grid as a net covering the earth. Each mesh has one and only one value that represents the characteristics of the pixel mainland table. This value is unique. Therefore, the main feature values in the pixel are used to represent the features of the entire pixel.

 

 

Roaming and Scaling

After adding the layer data you want to publish on the Internet, author provides some tools for you to view the data in more detail. Here, the roaming and scaling tools are:

1. Zoom to previous extent -- this tool is used to return to the view range after the previous scaling or roaming operation;

2. Zoom to full extent -- used to display all layers in the map View window;

3. Zoom to active layer-after activating a layer in TOC, click this tool to display the active layer in the full graph;

Note that many operations in ArcIMS are only valid for the active layer. For example, only the active layer can be identified when the identify tool is used. When a layer is activated, the name of the layer in TOC is surrounded by a dark gray rectangle. Click the name of a layer in TOC to activate the layer.

4. Zoom in-Zoom In The Box range defined by the mouse click or map display;

5. zoon out-narrow down the box range defined by the mouse click or map display.

6. Pan -- you can use this tool to drag a view in any direction at any time without changing the map scale.

 

 

Scale

Spatial data used in GIS can be stored in unprojected geographic coordinate systems (decimal longitude and latitude), or in projected flat coordinate systems X and Y. Projected data is stored in units of actual length (e.g. meters, feet. When storing data, you need to inform ArcIMS of the unit of data storage-either in decimal longitude and latitude, such as meters or feet. The unit of ArcIMS data storage must be told, which can be completed by setting the map unit.

The scale unit is the unit that ArcIMS uses to reflect the scale size or measurement. You can select any suitable unit (miles, feet, meters, kilometers, etc.) to set a scale unit for your map view.

The screen unit is a method of measuring the real distance on the display screen with a ruler (for example, 1 inch on the display screen indicates that the actual distance is 50 feet on the ground ). The display unit can be set to inches or centimeters.

After the unit is set in author, only the map unit is the unit that is finally written to the Axl file. Any other organization set for display is only used to help website programmers build a high-quality website.

 

Move Layers

When there are multiple layers in the layer list, you may need to adjust the order of the layers. The layers in the layer list are displayed in the order of bottom-up. It is important to remember this order, because some multilateral row layers overwrite the layers under the vertex. Traditionally, place the dot layer and line layer on the layer list, and place the multilateral row layer and image layer under the layer list. To change the order of layers, you can press and hold the layer to be moved with the left mouse button in the layer list, and then drag it up or down to the new position. You can also right-click the layer to be moved and choose move layer from the shortcut menu. In this way, you can directly move the layer up or down, or move to the top or bottom of the list.

 

Layer Properties

The layer is initially displayed in the default random color. The elements of the multilateral row are generally filled with solid, and the point mark is represented by a circular symbol. Of course, you want to display these vertices and polygon elements as you want. In this case, you need to modify the layer attribute to change the symbol display.

There are two ways to display layer properties: one is to right-click the layer to change the attribute and select the layer properties option from the pop-up environment menu; click the layer properties tool on the toolbar.

After the Layer Properties window is opened, three tabs are available. The symbols label can change the display method, style, color, and size of elements. There are three ways to display element data: Single Sign, gradient sign, and independent value.

Tags are used to automatically label elements based on Attribute fields. You can set the field, Font, size, and effect. The General tab displays basic information about the layer. You can change the name of the layer displayed in the page's layer list, and set the scale range of the element display.

 

Single symbol method

When this method is used in layer properties, under the symbols label, you can select one of the three drawing methods to draw elements. The first one is the single symbol method ), each element is displayed with the same symbol regardless of its attribute value.

For the point element layer, you can select the type, size, and color of the Point Symbol (circle, square, triangle, cross, star, or image.

For linear elements, you can select a line (solid line, broken line, dot line, and railway line), color, and width.

For polygon elements, fill styles include solid, transparent, horizontal lines, vertical lines, diagonal lines, and images. The image can use the. gif and. jpg files as the "Wallpaper" of the multilateral line layer ".

When selecting a color, you can select from 14 predefined colors, or use RGB (red, green, blue) or HSB (color, saturation, and brightness) the method can be used to customize the color or directly select from the color table.

You can click the up or down arrow to change the line width or point size.

 

Independent Value Method

Another method for displaying data by category is the unique value method. For a specified field (numeric or string), a unique symbol can be used to represent the unique value in the field. This method is suitable for displaying data with unique values such as country, state, or sales range.

For example, if you have geocoded 1000 Addresses and created a layer for potential customer distribution, there is no doubt that, you can use the customer name to uniquely identify these points. However, because each customer has a unique name, 1000 types of symbols are required. However, you can use "customer's favorite products" for classified display. In this way, you only need a few symbols to express more meanings.

ArcIMS can use many independent value classification methods to express elements. bountiful harvest, pastels, and minerals are three predefined color schemes. ArcIMS allows you to display each value in a random color or set a color. To change the color of any symbol, click the color or symbol under the symbols label.

In the unique value method, you can change the style type of all elements (point marking, line type, polygon filling mode ), you can also change the size or width of points and line elements.

 

 

Gradient notation

Another method for creating a topic chart in ArcIMS is the gradient symbol method. This method uses a series of gradient or gradient symbols to display different element types. It is suitable for displaying data with a certain change value or value range, such as temperature, population, and annual sales volume.

In author, you can select numeric fields for classification using gradient symbols, or change the number or range of classes so that all elements can be classified into a specific category, each type is displayed with a specific symbol.

ArcIMS uses the same interval method for data classification, that is, the range of sub-classes after classification is equal. The value range in author cannot be changed manually. In the following course, you will find that these values can be changed in the created Axl file.

For gradient data, you can define the size of the start and end color points or linear symbols. For example, you can create an American temperature distribution chart, which is expressed in blue in a cooler place, red indicates the hot area.

By default, the standard name displayed in TOC has the same range as the subclass value. You can manually enter text to change the annotation of each subclass. Due to Java restrictions, you must press the Enter key after entering each annotation to ensure that the annotation is correctly modified and changed.

 

 

ArcIMS analogy: Axl File

The Axl file is the final output of author. It describes the layers to be displayed and how they are displayed.

The Axl file produced by author can be used as a recipe for your favorite dish. The recipe generally contains a series of spices and describes the cooking methods of this dish in detail. Similarly, the Axl file contains a series of data layers that accurately describe how these layers are displayed. However, the Axl file does not describe the amount of data as the recipe shows the amount of each seasoning, because the amount of data is an attribute of the data itself.

Recipes and Axl files have other notable features. For example, a restaurant user can order shredded fish instead of shredded fish. Similarly, what ArcIMS customers need is not an Axl file, but a description of an existing Axl file (that is, map service ).

 

Axl File

The arc eXtensible Markup Language (Axl) file format defines a standard for data and HTML page storage. The Axl record format is the same as XML (Extensible Markup Language (XML.

The Axl file is the output file of author. When writing an Axl file, author records the data to be published, the storage location of the data, and how the data is displayed. The Axl file does not store real data layers, but only stores reference information about the data.

When you click "save" in author or click "Next Step" after the authoring process is completed in the Manager, the Axl file will be generated (the Axl file name is the same as the map file name specified when the site is first generated ).

The Axl file is a text file, which is similar to the project file (. Apr file) in ArcView and can be opened on the WordPad.

 

 

Axl file example

Carefully analyze the structure and format of the above Axl file. Note that the tag specifies the reference to the data and attributes. These Axl labels are pre-defined to implement relevant functions.

For example, find the <workspace> tag in the Axl File above. The tag is used to determine the data location. Note the label usage. They all use <XXX…> Start with <.... At the end of/xxx>, many header and tail identifiers appear in pairs, while some shapeworkspace labels only need one tag to contain the header and tail identifiers. Like an HTML file, an Axl file uses a nested tag structure. That is to say, a tag (such as <shape woekspace>) must end before its upper-level tag (such as <woekspace>) ends. For the sake of intuition, indentation is generally used to indicate the nested relationship. Though it is not necessary to write an Axl file in indent format, the indent format helps improve the readability of the Axl file.

<Shapeworkspace> specifies the exact location of the element data. In the preceding example, the sanfrancisco folder is used. The actual data of San Francisco is not stored in the Axl file, and only the location of its folder is stored here. Some attributes are also defined in <shapeworkspace>. These attributes are necessary to determine the parameters required for the tag. In this example, the name attribute specifies the internal name of the workspace, And the Directory attribute specifies the data location. Note: labels must be in upper case and attributes must be in lower case and placed in double quotation marks.

Let's look at some other labels. <Layer> label specifies the pizza layer in the sanfrancisco folder. <Simplemarkersymbol> the identifier defines the color of the pizza vertex element, the style type and size of the midpoint element of the pizza layer.

 

 

 

Create an Axl file in Manager

The process from generating an Axl file in the Manager to creating a website is different from the process of generating an Axl file through author. Essentially, the manager divides the Axl file generation into three steps:

1. Generate a map service -- select;

2. generate an Axl file-use the author interface to add and select a display symbol for the layer;

3. Create a map service-select a virtual server for the map service and start the map service.

After Authoring is started, the manager starts the map service. To design and browse a website, you must start a map service. The map service is only a view of the data to be published defined in the Axl file. It is not a physical file. Because the Axl file only stores the reference information of the data and how the data is expressed, the map service depends on the Axl file. However, the Axl file does not depend on the map service. When creating the map service, you must specify a virtual server.

 

 

Select Virtual Server

Traditionally, IMS runs in the following way: the client submits a request to the server, such as roaming or playing the server to respond to the request and returns a new image. However, ArcIMS is able to transmit image or vector data from the server to the client through a stream, which undoubtedly has many advantages.

Hosts file.

The element data stream method is a major improvement in Network-Based Graphics applications-it makes unprecedented GIS functions "common" on client computers ".

Through the element data stream, the customer requests new data to the server only when new geometric element information is required for roaming or scaling operations, the current and existing data within the scope of the cache has become part of the client's element cache, you can directly call it without having to re-request the server. Because many GIS functions have been embedded into the Website Based on the ArcIMS element data stream, the number of requests sent to the server at runtime is greatly reduced.

The performance of the ArcIMS site using element stream technology will be improved and more powerful. For example, you can perform map prompts and element editing.

Because of the complexity of the element data stream technology, there are also some additional requirements on the client-The client needs to support or download Java 2. At the same time, the client also requires support for Java applets. In general, it takes longer to wait because you need to download some items about applets at the beginning.