Practical 1

Using data from paper maps

In this practical you will:

You will need:

  1. Your zip disk containing data used in Practical 1
  2. A computer with internet access
  3. MapInfo software (at least version 5.5)
 

Open the OS Landline map of Little Wittenham.

  1. Open MapInfo. In the Quick Start dialogue box select Open a Table and press the Open button.

  2. Select the file Little Wittenham.TAB and click Open.

  3. Adjust the view of the Little Wittenham map as in Practical 1 so that you can see the area of the wood clearly in the centre of your screen.

  

Open a scanned version of a hand drawn paper map of Little Wittenham.

  1. Click here to download a copy of the hand drawn compartment map (compartment_map.gif). Your web browser will probably open compartment_map.gif in the current window. In order to download it you will have to right click on the link "Click here" and select Save Target as... (in Internet Explorer) or Save Link As... (in Netscape). Save the file in the "Data" folder on your zip disk. If you have a paper map of your own you could scan it yourself and save it as a raster image, a file with a .bmp, .jpg, .gif or other suitable extension.

  
save right click ns     save right click ie

  1. Before you open the raster image in MapInfo you need to establish the precise position of at least four control points. Go to MapInfo and select Map from the menu and then choose Options. A Map Options dialogue box will open in which there is a group of option buttons called Display in Status Bar. Select the button Cursor Location and click OK.

  2. You will now see that as you move the cursor over your map its precise position is displayed in the Status Bar at the bottom left hand of your screen.  Move the cursor to four easily identifiable points (I suggest you use the four corners of the wood) and record their positions. These will be your control points.

Register and digitise the raster image

  
  1. Now you will need to open the raster image in MapInfo. Select the File menu and then Open table... As an alternative you can use the Open Table button on the toolbar open table tool. In the available files compartment_map.gif will not be displayed as MapInfo by default will only show files with a .TAB extension, i.e. MapInfo tables. In order to open a scanned in picture you need to tell MapInfo what sort of file you are trying to open. In the Open Table dialogue box under types of files click on the drop down arrow and select Raster image. compartment_map.gif should now be displayed. To open compartment_map.gif over the top of the OS map in the Preferred View option select Current Mapper. Finally select compartment_map.gif and click Open.
raster select

 

  1. A window will open asking you whether you would like to display or register your image. Select Register. This will enable you to choose a coordinate system and link the raster image with the OS map.

 register or display

  1. An Image Registration dialogue box will open. Firstly click on Projection... to instruct MapInfo which coordinate system to apply to compartment_map.gif. In the Choose Projection dialogue box under Category select British Coordinate System and under Category Members select British National Grid. Click OK.

 

  1. Back in the Image Registration box, click New. If you move the mouse over the image of the paper map then a cross will appear instead of an arrow. Scroll across the image until you can see your first control point, for example the top left hand corner of Little Wittenham wood. The Add Control Point dialogue box will open. You can rename the point if you wish or leave it as "Pt. 1". Then enter Map X and Map Y values for the point. Click OK. Select 3 other points in the same way. You can use the scroll bars to view different parts of the map, and also use the "+" and "-" buttons to zoom in and zoom out of the map. When you are finished selecting points click OK.

  zoom + -

  1. An new layer should open in the current mapper showing the hand drawn map over the OS map. If not, then you will need to bring compartment_map.gif to the top layer. On the Main toolbar click the Layer Control button layer. In the Layer Control dialogue box select compartment_map and in the Reorder section click Up. Then click OK.

layer control diag

  1. Now that you have registered compartment_map.gif you will have created the file compartment_map.TAB in the same folder as compartment_map.gif, in this case in the "Data" folder on your zip disk. From now on if you want to open this raster image  in MapInfo you simply open the MapInfo table with the .TAB extension. There is no need to digitise or register the image again. You must keep all the files relating to compartment_map.gif together in the same folder as compartment_map.TAB. The TAB file will refer for information to compartment_map.gif and if you put the files in different places MapInfo will not know where to look.

  2. Save the workspace as compartment_map.wor. Instructions for saving a workspace can be found in Practical 1. In the next section you will need to convert the hand drawn map into a vector map that can be used in a GIS.

  

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Web page designed by Nick Brown and written by Caroline Bampfylde. Last updated on 14th February 2002. Any comments and suggestions to nick.brown@plants.ox.ac.uk or caroline.bampfylde@plants.ox.ac.uk.