The following information may help to convert a calibration file in a format recognized by Multiplans.
.map calibration file. Multiplans automatically recognizes .map calibration files that use the "Lat / Long" projection. If the .map uses another map projection, automatic conversion of the file by Multiplans may be inaccurate. In the latter case, open the .map file with a text editor to read calibration information. Alternatively, use OziExplorer to display the calibration information of the map (menu "Check calibration of map").
Map in format ECW: calibration information are contained within the file, and can be read using programs such as:
GDAL library (Mac, Linux, Windows): use the command line tool gdalinfo. (See KyngChaos to install this library on Mac).
Then simply use the information found in the header of the ECW file to write the ref.txt file, as explained in this example .
GeoTIFF format map: Use eg gdalinfo to read the calibration information, and proceed as in the case of ECW maps.
Map with a "world" calibration file .jpw, .tfw, .jgw, .jpegw or .bpw. These calibration files contain almost all the information needed for the calibration. The structure of these files is:
Calibration file .jpw, .tfw ...
<- Line 1: horizontal resolution (often in m/pixel)
<- Line 2: rotation
<- Line 3: rotation
<- Line 4: vertical resolution (ignore the minus sign!)
<- Line 5: X coordinate
<- Line 6: Y coordinate (the upper-left corner of map)
A "world" calibration file can be easily converted into a ref.txt calibration file: write the coordinates of the top-left point calibration for pixel position 0, 0, and use the keyword "resolution" . The only difficult part is identifying the map projection used by the map, a piece of information that has to be entered on the first line of the file ref.txt. (See document geocoded TIFF & JPEG files for more information about calibration files).
Calibration file ERS: A calibration file.ERS contains all the information necessary for referencing a map in an easily readable format.
Maps from a mapview sites.
If the website displays the coordinates of the point under the mouse, it is easy to determine calibration points on the map.