Working With The Scanned Maps

Tutorials Use ArcView Working With Images

Working With The Scanned Maps

You can create a new theme or update your data by adding a scanned map to a view and using it as a guide for editing and digitizing.

Steps for Putting a Snanned Map to a View ....

Step 1

Scan the map

Before you scan the plan or map, draw a box frame to show t he area you want to cover & made a sign on the top of left-hand side corner as a reference or starting point (0,0). Make sure your map is following the North arrow.

scanmap1.gif (10423 bytes)

Specify the name & location of the new folder to keep the scanned maps file or you also can put the files into a existing folder.
Use the Desk-Scan II or Corel Photo-Paint to scan the map. Then, save the file as TIFF format & put in the folder you create just now.

Example: Scan1.tif

Step 2

Find out the x, y coordinate

If you are update the existing map, you must find out the x & y coordinate of the sign you marked just now from the view in ArcView.
You can use the Pointer tool to points out the x & y coordinate of that sign. The x, y coordinate will be shown on the top of right-hand side of View windows.
Write down the value of x & y coordinate.

Example: y -6157.00

x -4300.21

Step 3

Set the x & y coordinate and the scale in WordPad

(Create the World File)

Create the World File. This is the file which ArcView uses to register the scanned image to the real world.
Go to Accessories, choose WordPad.
In WordPad, Choose New from File menu or just click the New button. In the dialog that appears next, choose Text Document as a New Document Type.

New Document Type:

Word 6 Document

Rich Text Document

Text Document

Unicode Text Document

Example:

1.05

0.00

-1.05

-4300.21

-6157.00

*1.05*	The dimension of a pixel in map units in the x direction (the x scale). To determine this scaling factor, first find a distinct object, e.g. house or road or some linear feature on both the GIS basemap (shapefile) and the scanned image. On the GIS map, use ArcView to measure the length of the object. Then examine the same feature in the scanned image (you can also view it with ArcView). Count the number of pixels for that object. The length of the object measured from the GIS basemap divided by the number of pixels will give you the scaling factor. If the pixels are not equal-sided squares, then you should find a linear feature running in the east-west direction for the x scale factor.
*0.00000*	Rotation term for column.
*0.00000*	Rotation term for column.
*-1.05*	The dimension of a pixel in map units in the y map units. See discussion on x scale factor above. Use a linear feature running in the north-south direction if pixels are not equal-sided squares.
*-4300.21*	The x coordinate of the center of the upper-left pixel in map units.
*-6157.00*	The y coordinate of the center of the upper-left pixel in map units.

The x & y coordinate value is the value you write down just now.
Go to the File menu, choose save as to save the document. The file name must be same as the file name of scanned map & put into the same folder.

Example: Scan1.tfw.txt (Text document)

Step 4

Change the format of the WordPad file

Example: Scan1.tfw

Step 5

Adding a snanned map to a view

Open the Project windows in ArcView.
Go to Theme menu, choose Add Theme or just click the Add Theme button .
In the dialogs that appears next, choose Image Data Source from the Data Source Types list.
Navigate to the directory that contains the scanned map you scan just now. Press .

Tips:

Make sure that the scanned image and the World File are in the same folder.
The names of the scanned image and the world file must be the same; e.g. TelukBahang.tif is the scanned image file and TelukBahang.tfw is the world file.
If you have added both the shapefile and the image file but see only one and not the other, click the Zoom To Full Extent button to see both. The image is probably not correctly registered to the basemap.