Manual – Old and New Map Images

When launching MapAnalyst, the OpenStreetMap is displayed in the right half of the window. OpenStreetMap can optionally be replaced by another map in raster format.

Import of Map Images

To import a map image (both old and new), it has to be available as a digital raster image in one of the following file formats: JPEG (.jpg), PNG, GIF, or BMP. It is recommended that you use the JPEG, PNG or GIF formats.

Choose File - Import Old Map Image or File - Import New Map Image to import a map image to the old or new map.

Scans of maps can be very large in terms of required memory. It is recommended that you down-sample your images to a maximum size of approximately 5000 by 5000 pixels. Large raster images might possibly slow down MapAnalyst, depending on the speed of your computer. The maximum possible size mainly depends on the amount of available memory.

Remove a Map Image

To remove a map image choose Edit - Remove Old Map Image or Remove New Map Image and Use OpenStreetMap. Neither the points nor the links that you have previously placed are affected by these commands. Note that when the new reference map is removed, the OpenStreetMap will be displayed.

Size and Scale of Maps

For a correct computation of the scale of the old map, it is important that the size of the old and the new map are correctly read by MapAnalyst. Use Maps > About the Maps… to verify MapAnalyst is using correct dimensions.

To determine the size of the old map, MapAnalyst uses the DPI information embedded in the image file. Depending on the software used to generate the image file, the DPI information may be missing or incorrect. It is highly recommended to use the "Measure Distance and Angle" tool from the toolbar or the Maps > About the Maps… menu command to verify that the size of the old map image is correct. If this is not the case, it is recommended to open the map image with Adobe Photoshop, adjust the image size, and and re-save the image using the JPEG format.

World Files for the New Reference Map

The new reference map image must be georeferenced, that is, the image needs a geographic reference. Otherwise the computations of the old map's scale will be incorrect. MapAnalyst reads a World file to georeference the new reference map. This is an ASCII text file containing information about the location and size of the new map. If your reference map image is not georeferenced, it is best to use a Geographic Information System to reference it and generate a World file.

The world file must have the same name as the image file, but differs in its extension:
jpg needs a jgw file
png needs a pgw file
gif needs a gfw file
bmp needs a bpw file
tif needs a tfw file

World files can be edited with a text editor capable of writing ASCII text files. World files consist of 6 lines of text:

Line 1: size of a pixel in x direction
Line 2: first rotation term (usually 0)
Line 3: second rotation term (usually 0)
Line 4: negative (!) size of a pixel in y direction
Line 5: x coordinate of centre of upper left pixel in map units
Line 6: y coordinate of centre of upper left pixel in map units

Note that MapAnalyst requires the pixel size to be equal in x and y direction. Additionally, both rotation terms (line 2 and 3) must be 0. Below is the content of a sample world file with a pixel size of 25 meters and the upper left pixel at x = 600,000 and y = 200,000.



Size of the Old Map and Optional World File for the Old Map

A world file is only required for the new reference map. For the old map, the DPI information embedded in the image file is used to determine the size of the image. It is highly recommended before you start analysing the old map you use the "Measure Distance and Angle" tool from the toolbar to verify that the size of both maps are correct.

In some rare cases it can be useful to work with a georeferenced old map. If the old map file has a corresponding world file, MapAnalyst imports this world file and ignores DPI information embedded in the image file. Use View > Old Map Display Coordinate Unit to switch to meters in the toolbar display.

Working with georeferenced “old” maps can be useful if you are not actually analysing an old map, but, for example, want to visualise deformation of map features. Examples include meandering rivers that change over time.