- Geographical Information Systems (GIS) were defined by Burrough (1996) as "a powerful set of tools for collecting, storing, retrieving, transforming and displaying spatial data from the real world." GIS include "a database system in which most of the data are spatially indexed" (Smith et al, 1987), and these data may be displayed as tables or maps in GIS software packages such as MapInfo.
- Geographical Information Systems may be either 'raster', i.e. a continuous surface stored as cells, or 'vector', stored as discrete point, line and polygon objects with attached attributes. MapInfo is a vector based GIS.
- Points - single data locations, with an x and y co-ordinate.
- Lines - connections between two points. A point may be seen as a line with only one set of x and y co-ordinates.
- Polygons, or regions - a closed area composed of points which are joined by lines.
- Attributes - the text attached to any point, line or polygon entity. This may be an address for a point representing a house, a name for a line representing a road, or a land use type for a region representing a forest.
To use a coverage, or map layer, in MapInfo, a number of files are required.
Important: Do not delete any of these files for a given coverage. MapInfo requires all of them for a coverage to work. Only if you wish to delete the entire coverage and not use it again should you delete any of these files, in which case delete all the files associated with a given coverage name. Otherwise, should you delete one, you will probably lose your work.
- filename.tab - a MapInfo table.
- filename.map - the co-ordinates of the data.
- filename.dat - the attribute data.
- filename.id - an index file containing the links between objects in the .map file and attributes in the .dat file.
- filename.ind - an index file for the .dat file, in order to allow searches.
You may also have:
- filename.wor - a workspace, which saves information about the location of open tables and maps.
- It is important to individually save all tables and maps which have been edited before exiting MapInfo, even if you do save the workspace. Deleting a workspace will not result in the loss of data, as the tables which were used in the workspace remain unmodified. However, maps, graphs, layouts and the like would be lost if they had not been individually saved. If there are unsaved tables, MapInfo will prompt the user with a save dialog box on exiting the program.
The MapInfo window
Open MapInfo Professional version 7.5 now: Start > Programs > MapInfo > MapInfo Professional 7.5
If you are using the free trial version, a dialog box will appear asking you to enter 'Enter Licence Key' if you have purchased the full version of MapInfo, in which case enter the key and click Update Licence Now. Alternatively, click Continue Trial Period.
A dialog box will appear inviting you to open either a table or a workspace. For now, click cancel. Take a look at the MapInfo window.
MapInfo has a title bar including minimise, restore or maximise, and close buttons.
Below the title bar is the menu bar with the following menus.
Relevant menu items are discussed in the appropriate sections of the tutorial.
- File: Menu commands which are normally found in the file menu of other applications are also found here for MapInfo.
- Edit: This is also the case for the Edit menu.
- Tools: The Tools menu is an important feature of MapInfo. It is from here that you may run programs from MapInfo's programming language, MapBasic (Section Four, Part Three), load new tools, launch the Mapping Wizard Tool, view the Metadata (data about the data, such as its source) and access the Universal Translator (Section Three, Part Four).
- Objects: The Objects menu does not by default have any active items, and is used only for advanced tasks.
- Query: The Query menu allows the selection of certain entities by a number of methods (Section Four, Part One).
- Table: The Table menu allows manipulation of data tables, such as adding new columns (Section Two, Part Three), importing and exporting tables, and geocoding.
- Options: The Options menu allows the user to alter aesthetic aspects of their maps, such as line and symbol styles.
- Window: The Window menu is used to create new windows of different types, and arrange existing windows on the screen.
- Help: Opens MapInfo's help system. This is a very useful feature, especially its index.
Other menus may appear on the menu bar during your use of MapInfo. For example, should you create a map window (Section Three, Part One), a Map menu will appear.
The main area of the MapInfo window is taken up by the workspace. This area forms a background on which browsers, maps, legends, graphs and layouts may be opened, each in a new window.
Below the menu bar is a toolbar which features the following icons, from left to right:
- New Table: Creates a new MapInfo table, and invites you to open either a new browser window or new map window in which to view this.
- Open: Opens a MapInfo table.
- Open WMS Table: Opens a sample data table from the MapInfo server. WMS stands for Web Mapping Services. It is necessary to be connected to the internet in order for this to work.
- Save Table: Saves the table.
- Print Window: Prints the active window. This may be a map, legend, browser, layout, graph etc.
- Cut: Cuts the selected object or area
- Copy: Copies the selected object or area.
- Paste: Pastes objects or areas which have been cut or copied.
- Undo: Undoes the last action performed, where possible.
- New Browser: Creates a new browser window.
- New Mapper: Creates a new map window.
- New Grapher: Creates a new graph window.
- New Layout: Creates a new layout window.
- New Redistricter: Creates a new redistrict window.
- Help: Another way to open MapInfo's Help system.
These buttons duplicate commonly used menu items.
MapInfo also has floating toolbars. The Main and Drawing toolbars appear by default when MapInfo is opened. Other toolbars may be added using the Toolbars command in the Options menu (Options > Toolbars). The standard toolbar may be dragged downwards to form a floating toolbar. Floating toolbars may be dragged upwards to sit beneath the menu bar.
||The main toolbar has selection tools (Section Four, Part One), view tools such as zoom in, zoom out, and pan, layer management tools (Section Three, Part One), and other tools such as a meaurement tool, statistics tool and legend control tools (Section Three, Part One).
|| The drawing toolbar contains tools for drawing new line and region entities, and for other features such as adding text.
|| The tools toolbar by default includes tools such as Run MapBasic program (also accessed by Tools > Run MapBasic Program, discussed in Section Four, Part Three, and Run Mapping Wizard Tool (Tools > Mapping Wizard Tool > Run Mapping Wizard Tool). However, more tools may be added to this toolbar using Tools > Tool Manager, discussed in Section Three, Part Three.
Go to Mapping Wizard Tool
|| DBMS stands for Database Management System.
The DBMS toolbar allows tables external to MapInfo to be linked seamlessly into MapInfo so that they may be manipulated using MapInfo's controls. This toolbar is not often used, but it is an important feature to be aware of.
However, before we can play with any of these features, we must first import some data.
The first thing to do is to obtain some data in a format suitable to use in MapInfo, or which are suitable to be converted into these formats.
MapInfo may import files in the following formats:
- .tab - MapInfo tables.
- .mif and .mid - MapInfo interchange files. .mif files hold co-ordinate data, while .mid files hold attribute data.
- Database files - Microsoft Excel, Microsoft Access, Lotus, dBASE.
- Graphics - .gif, .jpg, .bmp, .tif etc.
Nomis is run by the University of Durham of behalf of the Office for National Statistics(ONS). It provides Labour Force Survey data for variables such as employment and claimant counts.
Accounts are free and available to everyone, is as the case for all ONS data.
- Use a web browser to navigate to http://www.nomisweb.co.uk. It is not necessary to register with Nomisweb in order to access their data. However, if you do not have an account and would like one, choose the 'register with us' link in the box at the top left, and follow the necessary steps. Your username will be a combination of numbers and letters assigned to you by Nomisweb, and the site allows you to select your own password. These will be sent to you in an email confirming your registration, from which you must follow a link to activate your account.
- The easiest way to select data from Nomisweb is using the Wizard. Click on the Wizard Query link in the Detailed Statistics box in the centre of the screen. This will ask you to log in, either using your username and password, or as a guest.
- Data may be selected from popular datasets, by theme, or by geography, by following the links. We will use the example of claimant count for the most recent month for the Bradford district.
- Select the link 'claimant count with rates and proportions' from popular datasets. Click next to begin selecting data.
- By default, the most recent data are selected. However, data for any range of dates may be selected at this stage. Click next.
- The next stage is to select the geography from a list of choices. We will use 1991 frozen wards for this example, although the 2003 ward boundaries have recently become available for data from February 2004 onwards. Select this link. Choose Bradford from the drop down menu. This will give you a list of wards in the Bradford district. Click Select All, then click Next.
- Select the rates or proportions of the population you wish to download, and click next.
- Select whether you wish to download data for males, females or the total population, and click next.
- The next window shows a summary of the selection you have made. If you are not happy with it, now is the time to go back and change it. Click next.
- The final stage of the wizard allows you to select the format in which you wish to download your data. Select comma separated values from the drop down menu. This is crucial to the data easily being imported into MapInfo. Click Download data. Save the comma separated values (.csv) file.
- Use Microsoft Excel to open the .csv file, and save it as an Excel file, .xls. Deleting the .csv file will not affect the .xls file. This file may then be imported into MapInfo (Section Two, Part Two), and appended to a table which has boundary data for the same geography (Section Two, Part Three).
Casweb is a source of data for 1981, 1991 and 2001 censuses. Data are available at output levels right down to Enumeration District (ED) for 1991 data or Output Area (OA) for 2001 data. Data are stored by table, and these tables are searchable for keywords.
To access Casweb you will need an Athens username and password. These are available to members of the academic community, including reserach councils, free of charge, by contacting the Athens administrator for your institution, a list of which may be found at http://www.athensams.net/dsp/sitelist.html. Institutions which are funded by the Joint Information Systems Committee (JISC) or National Health Service (NHS) may also apply for access to Athens services, although there is a charge for this, details of which are available by emailing email@example.com. The Athens website provides further information. As the Athens username and password give access to a wide variety of information from the internet, it is well worth getting one.
1991 Casweb Data
- Use a web browser to navigate to http://www.census.ac.uk/casweb. Log in using your Athens username and password.
- Select the type of data you wish to download, for example, 2001 Census for Great Britain or 1991 Great Britain SAS (Small Area Statistics) and LBS (Local Base Statistics). For this example we will download ward level data on the population of Bradford by ethnic group for 1991. This example dataset will be used throughout the tutorial.
- Select the blue link to the 1991 Great Britain SAS and LBS (with digital boundary data).
- The data download process for Casweb in the three user friendly steps. You can tell which step you are in from the tab on the left of the window.
- Step One: Define Study Area Study areas may be selected from a List View or a Map View. When you know the name of the area you wish to download data for, the List View is quicker, so this is what we will use.
- Select England, and click the Select Counties/Regions button. Select 08 West Yorkshire and click the Select Districts button. If you wish to clear your selections at any point, press the Reset button.
- Select 08CX Bradford. There is an option to select data for Wards/Postcode sectors, and then for EDs/OAs (Enumeration Districts/Output Areas). However, as we wish to download data for the entire Bradford district, we now move on to Select Output Level.
- The output level allows the user to choose whether they wish to download data at every scale down from the one they have selected. In this case, we can download data for the whole district, by ward, or by ED. If we had chosen Select Output Level after we had selected England or West Yorkshire, we would also have the choice of downloading data by county. For this exercise we will download data by ward, as district level data are too coarse a resolution and ED level data would be too fine a resolution to produce a clear map for the whole district. Consider the use of the data when selecting the output level.
- Step Two: Select Data Data may be selected from census tables which are listed in the drop down list. Data may also be selected by searching for the variable required. Select table 01: Population bases. From this table we will get the total population of each ward, which we can later use to calculate the percentage of the population which each ethnic group forms.
- Maximise the window if you cannot see the Select Variables button to the right of the list of tables. Leave the SAS radio button selected, and leave the default table view as Grid View. Press the Select Variables button.
- Select box 1 in the top left corner of the table. This represents the total residents. We know we will get this figure for each ward when we download the data, as we have already set our output level to ward.
- Click the Add Variables to Data Selection button above the table, and wait. s010001 will appear in the variable list on the right of the screen.
- Important: The names assigned to the variables represent the cell within the table from which they are selected, and as such are combinations of letters and numbers which are meaningless to the user. Select the variable s010001 so that it is highlighed in blue if it is not already, and click the rename button in the variable list frame. Give your variable a meaningful name, so that you know what it represents when you come to look at it later, for example, totalpop. The more variables you have, the more important it becomes to do this.
- Data from several tables may be selected and downloaded as one file. Use the blue link above the table, which allows you to click here to select another table. This will take you back to the list of tables.
- Select table 06: Ethnic Group, and press the Select Variables button.
- Choosing the checkbox in the leftmost, grey, column will select the entire row. Similarly, selecting the checkbox in the top, grey, row will select the entire column. There is a Select All button for selecting the entire table. Clicking a checkbox again once it is selected will deselect it, but there is a Clear All button at the top for undoing larger mistakes and starting again with that table from scratch.
- Select the top row of the table, total persons. Click in the checkbox for persons born in Ireland to deselect it. Click the Add Variables to Data Selection button.
- Rename the variables in the variable list, making sure they have self explanatory titles.
- Choose the Select All button in the variable list frame, then the Get Data button.
2001 Casweb data
- Wait while the Casweb Data Engine runs. You will then be taken to Step Three: Output Data.
- By default, Casweb will produce a preview of the top left hand corner of your data table. Close this if you are happy with it. If not, return to steps one or two to correct the geography or variable selection.
- Enter a filename in the box to the right of the Save Data button. Choose a self explanatory filename such as ethnicward. In windows explorer, create a directory in which to save the file. This should also have a self explanatory name, such as Bradford91, especially if you will be downloading or otherwise obtaining data for other districts or years, in which case it is very helpful to have a hierarchical directory structure matching the geography.
- Return to the output data page. Select the Mappable button, as the default is plain text. Ensure the type is set to MapInfo, and set the generalisation to none. Set the download file format (file compression) to zip. Check over these options.
- Click the Save Data button. Wait while the Casweb Data Engine runs. Press the button (filename.zip) to download the file.
- Choose Save, and then save the file to the appropriate directory.
- Using Windows Explorer or My Computer, naviagte to the directory where you have saved your zip file. Right click on it, and choose Extract to...
- You may then have to agree to the licence agreement of Winzip. Do so, and choose the directory into which you wish to extract your file. Ideally this should be the same directory, or a subdirectory of this. Click Extract. You will have two files - filename.mid, and filename.mif, which are ready to be used in MapInfo.
- The 2001 data do not, as yet, have boundary data attached. However, these may still be used in MapInfo, as they may be appended to tables of 1991 data, using the 1991 census area boundaries as approximations for those of 2001. This process is discussed in Section Two, Part Three.
- 2001 data may be downloaded from Casweb by following a very similar process to 1991 data. We will download the population of Bradford by ethnic group at ward level for 2001 now, as we will use this in Section Two, Part Three.
- After logging in, choose the link to 2001 Key Statistics and Standard Tables Datasets for England and Wales.
- Select the country, England, and click Start.
- Step One: Define Study Area Choose Yorkshire and the Humber, then click Select Counties. Choose West Yorkshire, then click Select Districts. Choose Bradford, the click Select Output Level. For this example we will use CAS ward. Click Select Data.
- Step Two: Select Data At CAS ward level only Key Statistics may be selected, and not Standard Tables. Select the appropriate data by the same process as for the 1991 data.
- If you choose ST ward instead of CAS ward, you will be able to select data from the standard tables. These tables represent cross tabulted variables, such as "Sex and Age by Economic Activity." While these tables are highly useful for some types of work, the file sizes involved are very large.
- Step Three: Output Data The process is the same as for the 1991 data. However, there is no option to save the data as a MapInfo file. Instead, save your data as a comma separated values file (.csv). Open the file in Excel, and save it as an Excel file (.xls). Deleting the .csv file will not affect the .xls file. This file may then be imported into MapInfo (Section Two, Part Two), and appended to a table which has boundary data for the same geography (Section Two, Part Three).
- The 2001 data have a Visualisation option. However, this lacks the flexibility of downloading the data into a program such as MapInfo and performing analysis. It is also particularly slow on internet connections which are not Broadband.
- Beneath the button for downloading the data appears the following:
- Copy and paste the citation into a text file as you will need it to add to any output you produce from this data. This is discussed further in Section Three, Part Three.
UK Borders "provides digitised boundary datasets of the UK, available in many GIS formats" (http://edina.ac.uk/ukborders/description). As with Casweb, you will need an Athens username and password.
Data from UK Borders are very useful for attaching to datasets which are not georeferenced. This is discussed in Section Two, Part Three.
- Use a web browser to navigate to http://edina.ac.uk/ukborders.
- Login using your Athens username and password, using the grey login button at the top. If you would like a national datset, such as English wards 1991, choose the Easy Download link.
- Select the English wards 1991 link. Choose MapInfo Mif/Mid from the table, and select the zip file.
- File sizes for national datasets are extremely large. Do not download such a datset unless you are certain you need it.
- If you do not want a national dataset, choose the Original UK Borders link instead of the Easy Download link. It is a less simple process, but allows you to download only the data you need. We will download some 1991 ward boundary data for Bradford.
- Choose the Limit Country button, and select England. Choose the Limit Geography button, and select census. You may also make a selection from the Limit Date button, but unless you want historical data it is usually not worth it.
- Choose the Select Button next to Available Boundary Types. Your previous limitations mean you will get a far shorter list of options than you would otherwise have done.
- Select Census Wards, and choose the Find Areas With Boundary Data button.
- Select West Yorkshire from the drop down list, and choose Search for Boundary Data. Some boundary types will let you select at dsitrict rather than county level.
- Select the 1991 data from the drop down list, and click the Choose Extraction Method button.
- Make sure the precision is set to single, and the generalisation to none. Choose MapInfo MIF/MID for the export format. Make sure the file output is set to separate and the archiving method to none. Click the Confirm Boundary Data Extraction button.
- Click the Extract Boundary Data button, and wait. Click on the link for each of the files you are to download, and save the files into a directory of your choice.
- Files which make up the same coverage must be saved in the same directory, e.g. filename.mid, filename.mif and filename.lst. These files are then ready to be imported into MapInfo in Section Two, Part Two.
- UK Borders have the 2001 boundary data, but as yet the licence agreement has not been finalised. These data will be available soon.
Opening and Importing Tables
MapInfo tables (.tab)
MapInfo tables with which we can work have the extension .tab (for example, filename.tab). However, much of the data we acquired in Section Two, Part One were in other file formats such as Excel (.xls) or MapInfo Interchange format (.mif and .mid), and must therefore be converted into .tab files before we can begin to use them in MapInfo.
| Opening tables in different file formats for making maps and graphs may also be done in stage 1, Data, and stage 2, Maps, of the Mapping Wizard Tool.
To open a MapInfo table (.tab), go to File > Open. Navigate to the directory where the table is stored, select it, and click Open.
MapInfo Interchange Format (.mif and .mid)
- In Section Two, Part One we saw that data obtained from Casweb and UK Borders are in MapInfo Interchange Format, providing a .mif and .mid file for each coverage. Data which is supplied to you from other sources are also likely to come in this format. We will convert these two files into one MapInfo table, a .tab file.
- Open MapInfo (Start > Programs > MapInfo > MapInfo Professional 7.5). Go to Table > Import.
- Navigate to the directory where your .mif file is stored. Open the .mif file.
- The Import Into Table dialog box will appear asking you to save the .mif file as a .tab file. It is adivsable to use the same filename. Save the .mif file as a .tab file now.
- The table can now be opened using File > Open.
- This procedure also applies to .dxf files, .img files and Ordnance Survey MasterMap files (.gml).
Excel files (.xls)
- In Section Two, Part One we saw that data obtained from Nomisweb are in comma separated values (.csv) files, which we converted into Microsoft Excel (.xls) files. Much other data are available in this format, from a variety of sources. Older data are particularly likely to be in .csv format, for example, 1981 census data available on CD-ROM. We will convert a .xls file to a MapInfo table, a .tab file.
- Go to File > Open. Navigate to the directory where your Excel file is stored. From the drop down menu Files of Type, select Microsoft Excel (*.xls). Select your Excel file and click Open.
- The Excel Information dialog box appears, asking for the range of cells in the Excel sheet which contain the data you wish to import. By default this is the whole sheet. If the column headings are in the top row of the Excel sheet, tick the Use Row Above Selected Range for Column Titles button. Click OK. The table now opens in a browser.
- If your Excel file is not in this format, e.g. if there are extra rows of headings, edit a copy of your Excel sheet (in Excel) so that it has one row of headings only, and no other text than the headings and the data itself, before attempting to import it into MapInfo.
- ArcGIS is another piece of GIS software. It has some similarities to MapInfo. It has many features which MapInfo does not have, although most of these are related to analysis of the physical environment, for example, producing Digital Elevation Models (DEMs), viewsheds and stream networks. However, it is much more complex to use than MapInfo, requires far greater computing power, extensive memory, high processor speed and the latest operating system, and as such is far more expensive to buy, and less user friendly, particularly to non GIS specialists. However, data may be moved between ArcGIS and MapInfo, and vice versa.
- To import ArcGIS data (.e00 files) into MapInfo go to Tools > ArcLink > ARCINFO->MapInfo.
- In the left hand field, choose the files you wish to export from ArcGIS to bring into MapInfo. Use the select all button to select all the files in the current directory. Use the right hand field to choose where to save them. It is advisable to leave all the boxes checked.
- Click Translate.
Appending Columns of Data to Mappable Tables
It may be that the data you open in MapInfo is already attached to boundary data, in which case, ignore this section entirely! However, you may have data in spreadsheets and other tables imported into MapInfo which does not have attached boundary data. You may still produce graphs (Section Three, Part Two) or run queries (Section Four, Part One) on these data. However, if you wish to use these data to make maps, you must combine the tables without boundary data with a table of the same geography which has boundary data attached.
Firstly, we need to add new data fields to the existing tables which contain the boundary data, to contain the new data we wish to add. Do not underestimate the amount of time this may take if you have a lot of data to add.
- Table > Maintenance > Table Structure: A dialog box appears, showing a list of fields, with their name and type. Don't worry about the checkboxes in the indexed column, but do not uncheck any boxes that are already checked.
- Click the Add Field button. A field appears at the bottom of the list. Give your new field a name, preferably the same name as the column of data in the table you wish to import data from. Choose an appropriate type for your data, for example, character, integer (whole numbers) or float (decimal numbers).
- Do this for each new column of data you wish to add. If you wish to remove a field, first make sure it is selected and click the Remove Field button.
- Make sure the Table is Mappable checkbox on the right is ticked. Click OK.
- Table > Update Column: A dialog box appears.
- For Table to Update, make sure the table to which you have just added new fields to receive the data is selected.
- You can only transfer one column of data at a time. It is easiest to work from left to right of the table, i.e. top to bottom of the drop down list. In Column to Update, select the leftmost column of those you have just added. In Get Value from Table, select the table where the value you want to get is now.
- There is also an option to add a value to the column which is not from another table. If the value is the same for all the records, type it in the Value textbox. If not, choose Assist. The Expression dialog box appears. Alternatively, you can create an expression during the mapping process itself. The former is better if you want to store the values and use them more than once, whereas the latter is quicker if you do not.
- You can add values from several different tables to one mappable table, by changing the selection in Get Value from Table. Your original tables are unaffected by having their values added to other tables, as this process copies rather than cuts their values.
The processes described in section two have greater potential when used in combination than individually. Downloaded data may be opened directly in MapInfo, or have to be converted into a suitable file type and then imported. Data which are not mappable may be added to tables of the same geography which are. This allows greater flexibility in the types of data that can be used in MapInfo.
Once your MapInfo table is complete, you can finally begin making maps!
Creating Thematic Maps
Thematic maps are maps which are of one particular variable. This may be, for example, a map showing the population of each ward. Producing professional thematic maps is one of MapInfo's great strengths.
Creating thematic maps
- Make sure the table or tables from which you wish to create thematic maps are open.
- Window > New Map Window or alternatively use the New Mapper icon on the toolbar. When your new map appears, right click on the map and select View Entire Layer so that the map fits the window.
- Open a new map window for every thematic map you wish to create. This way, your original map is left blank and can be used as a base map from which to create further maps.
Map > Create Thematic Map
MapInfo has a user friendly three stage wizard to create thematic maps.
| The Create Thematic Map wizard may also be accessed by choosing the Create Thematic Layer option from stage 3, Analyse, of the Mapping Wizard Tool.
- Step One: Choosing the type of map and the colour scheme.
- From the selection of buttons down the left hand side of the wizard, select the type of map you want. Different types of map are appropriate for different types of data. The top button, ranges, is selected by default. We will leave this selected for our example, as we are going to make maps of the different ethnic groups in Bradford in terms of their percentage of the population at ward level.
- Ranged maps are appropriate for discrete variables, i.e. variables for which there is one value for a whole spatial unit and the value for adjacent spatial units is different. Pie chart maps are appropriate for representing multiple varibales, such as if we had chosen to represent all the ethnic groups as a percentage of the population at ward level on just one map. Grid maps are appropriate for mapping continuous surfaces, i.e. ones which change gradually, such as population surfaces interpolted from other variables. 3D maps are more appropriate when the data will be viewed on screen than when the data are to be printed out.
- Also available are bar chart and pie chart maps, which produce a graph in each geographical area (such as a ward), graduated symbol maps, which show the count of the data for the chosen variable within each geographical area as a symbol, the size of which varies according to the count, dot density maps, where the density increases according to the count, individual maps, where each geographical area has its own colour, and grid maps, which show variables as a continuous surface as one would see with a raster dataset. These, however, may be difficult to interpret.
- Leave the range button selected. From the list in the centre, choose a colour scheme for your map. This is previewed in the panel on the right.
- Don't worry if you can't find a colour scheme that is exactly what you want. These colour schemes are just a starting point, and you may change individual colours later.
- When you are happy with your selection, click next.
If you are unhappy with the ranges, styles or legend select Map > Modify Thematic Map, after making sure the map you wish to modify is the active window. This brings up a dialog box which is the same as step three of the Create Thematic Map wizard, from which you can make changes. If you wish to change something from steps one or two you will have to start again.
Once you have made your map, an important feature of MapInfo is Map > Layer Control.
A map in a GIS may be made up of several layers. For example, a map of the British Isles may have a region layer showing the outline of the British Isles, a line layer showing major roads, a point layer showing major settlements and an attribute layer showing text labels for the points and lines. Layer control allows the user to add, remove, reorder and customise layers.
From left to right, the checkboxes for each layer represent:
- Cosmetic Layer: This is the topmost, transparent, layer, which cannot be moved or deleted. It is here that titles etc may be added.
- Visibility: Can the layer be viewed in the current map window? If not, it may mean that the table containing the data for that layer is not open.
- Editable: This must be checked in order to be able to make changes to a layer.
- Selectable: Objects must be selected if they are to be used in analysis such as queries (Section Four, Part One). More than one layer may be selectable at the same time. If a layer is editable it is automatically selectable.
- Auto-label: Labels the layer with the first column of the data in the browser, i.e. with the leftmost column of the data table. This feature is unchecked by default.
- The first column in the table is normally the census area code. Labelling the map with this is often highly unhelpful. Make sure auto-label is checked for the layer you wish to add labels to, then choose the Label button at the right of the dialog box. From the Label With... drop down menu, choose the column you wish to label your features with. For census data, zone name is far more useful than zone ID, the default. This dialog box also allows you to choose the font and size for your labels using the Style (Aa) button, and to choose where you want the labels relative to the feature they are labelling. Click OK when you are happy. Click OK again to exit Layer Control. Labels may then be dragged into position and rotated if necessary. Individual labels may be altered by double clicking on them, for example, to split a ward name into two lines of text. However, to make changes to all the labels you will need to return to the Layer Control dialog box. The Label tool on the main toolbar may be used to add individual labels.
- The Display button brings up a dialog box allowing the user to override the default settings of the map composition, such as colour schemes and fonts. These changes may be applied only to the current session, or changed for future use.
- Use the Add button to add a new data layer to the map composition, and the Remove button to remove an existing layer.
- Click OK to exit Layer Control. The selected changes will then be applied.
- The Info Tool on the Main Toolbar (an i) is also important. Select this, and then click on any entity of interest in the map. The Info Tool brings up information about the entity. On the example map above, clicking on a ward brings up the zone ID, zone name and total population. In a more complex map, the Info Tool would bring up information about all the thematic layers. Click the Pointer Tool on the Main Toolber to exit the Info Tool.
- The Distance Tool on the Main Toolbar (the one which looks like a ruler) may also be of use. Select this, then use it to draw a line along which you would like the distance measured. The distance appears in a dialog box. Lines may have many nodes, each created by clicking the mouse. Double click to begin a new distance line. Click the Pointer Tool on the Main Toolbar to exit the Distance Tool.
- Hold the mouse pointer over a tool on any of the toolbars to see what it does.