MapInfo is a powerful and simple desktop map information system, which has basic operations such as graphic input and editing, graphic query and display, database operation, spatial analysis and graphic output. The system adopts menu-driven graphical user interface, and provides users with five toolbars (main toolbar, drawing toolbar, common toolbar, ODBC toolbar and MapBasic toolbar). Users enter the dialogue state through commands on the menu bar or ammonium buttons on the toolbar. The view table windows provided by the system include: map window, browsing window, statistics window and layout window, which help to output the design, and the output results can be easily output to a printer or plotter.
I. Graphic input and editing
The input of graphics is to digitize or convert all kinds of map information data to get the basic graphic data organization table of MapInfo. With different data sources, you can input them through handheld digitizers, scanners or other standard data formats. Such as AutoCAD (. DXF and. DWG)、Intergraph(。 DGN), ArcView shape data of ESRI, etc.
Using the drawing toolbar provided by MapInfo, the key points of digital input and map editing are as follows:
1. Set the coordinate system, projection, map direction and unit correctly.
MapInfo supports a variety of map projection methods. When users digitize a map, they must first set the coordinate system and projection used by the map. Because most maps indicate these two items in the legend, users can choose the coordinate system provided by MapInfo (stored in the text file MapInfo). PRJ) and modify MAPINFOW. PRJ gets a new coordinate system. To display raster map in MapInfo, you must register the image and set the projection for it. Because the process of projecting the map is usually not completely reversible, the copy should be backed up; Secondly, according to the selected coordinate system, set the map units used, for example, the map coordinates will be displayed in degrees in the latitude and longitude projection.
2. Set control point coordinates
In order to correctly explain the position of the digitizer moving head when tracking the map, it is necessary to set the coordinate parameters of the control points on the map. Select at least 4 control points. The more control points, the more accurate the coordinate transformation from digitizer to map. The selected control points have good discreteness, such as not being in a straight line. You can add, modify and delete control points in the system and save them in the workspace.
3. Drawing and editing tools
MapInfo has a complete set of drawing and editing tools, as shown in Figure 8-2. When editing a layer, you should first choose the command Layer Control from the map menu or use the tool button Layer Control to make the layer editable.
4. Edit the map by shaping geographical elements.
The map editing method can reshape areas, polylines, lines, arcs and points on the map layer. You can do this by moving, adding and deleting nodes that define line segments, or by copying and pasting selected nodes to create new points, lines and polylines. In the editing process, you can also use the function of converting area and polyline to view the nodes of area objects, or use auxiliary editing functions such as merging, dividing, erasing and overlapping nodes.
5. Use the automatic map tracking function.
Using the function of automatic tracking objects, the repeated boundaries can be automatically tracked to avoid repeated digitization. Turn on alignment (with the S key) to activate automatic tracking. Automatic tracking is not suitable for tracking rectangles, arcs, ellipses and other graphics made by drawing tools.
Second, MapInfo data table management
In MapInfo, a database is called a table, which can be used to create, store, query and display attribute data. One kind is data table, which can be divided into data table containing graphic (map) objects and data table without graphic objects, such as spreadsheet or external data table; The other table is a raster table, which is an image that can only be displayed in the map window, and there is no table structure such as records, fields and indexes of the data table. Here we only discuss the operation of data table.
1. Transmission of external data
MapInfo can call dBASE database, MS Excel spreadsheet, MS Access database, Lotus 1-2-3 and ASCll files. Select the file type in the Open Table window of File-> Open on the menu. The external table that enters the system must be saved as a MapInfo table with the Save As command under the File menu before editing.
2. Data table maintenance
In MapInfo, you can directly change the structure of the data table, such as adding or deleting fields; Change the order, name, type, width or index of fields. Set or determine the projection of the table from the dialog box; You can also delete tables, rename tables, and compact table structures to reduce disk space.
3. Operation of data table
MapInfo's table operation commands (except query) are all concentrated in the menu item "Table", mainly including:
(1) Create a new table, and add, modify, display and delete data records;
(2) Update column command is used to update the table quickly and intuitively. Select an object first, and then select table-> update column on the menu to fill in the update column dialog box.
(MapInfo provides many powerful aggregation functions for deriving new information. Aggregation functions include:
Average calculates the average value;
Count calculates the number of records in a group;
Minimum finds the minimum value of all records in the group;
Maximum Find the maximum value of all records in a group;
Sum calculates the sum of all record values in a group;
When calculating the average, the weighted average gives one value a higher weight than another;
Adjust the total calculation according to the number of one object in another;
Proportional average adjusts the average calculation according to how many objects are in another object;
Proportional weighting is calculated by adjusting the weighted average according to the proportion of one object in another.
(4) Geocoding This is a way to display the original non-cartographic database records in the map, so as to view the map distribution of data. In order to observe the data on the map, we must first assign positioning coordinates to each record to match the data in the record with the map. There are several different methods of geocoding, and the method of "geocoding by boundary" is explained here. The "boundary" here refers to a closed area or region. The essence of "geocoding by boundary" is to assign the X and Y coordinates of the boundary center to each data record in the table, so that the data records are displayed in the map window with the symbols specified by each boundary center. After geocoding, you can use the find command to locate a single record or object.
Third, the query function
MapInfo system provides users with powerful and flexible query function, which is called selection function in the system. You can find the information of the corresponding data table directly from the map through selection, or you can use the SQL selection provided by the system to find the corresponding data and map information from the data table. The system uses a temporary table (selection table) to store the selection results. For temporary tables, you can do many operations on the basic table, such as browsing, counting, copying or editing the table, and you can further generate new choices.
1. Select from the map
(1) Use the tools and menu commands in the main toolbar to make a selection. The main selection tools are:
Any of the above selection tools can select multiple or all objects (hold down the Shift key when selecting multiple objects, and click the objects to be selected one by one); You can also select all objects by choosing Select All from the Query menu. Select the "Don't Select" command to cancel all selected objects. When you want to view the information of the selected data, you can call up the dialog box from the "New Browse Window" command and select the "Selection Table" of the selected data.
(2) Use tools to view map information, such as using information tools to view data information corresponding to hit map objects; Use the Legend tool to view the legend used by the current map; Use the ruler tool to calculate and display the distance between points on the map.
2. Use SQL Select to make a selection.
(1) Select command
You can use the Select command on the Query menu to query a single basic table. According to the conditions created by the user, select the results from the table and display the map objects of the selected records in the map window. The selected table, like other tables, can be browsed, queried, mapped or made into statistical charts. Use the Save As command to create the result table.
(2)SQL selection command
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