The map file header starts at offset zero in the file and is defined
as:
The oSignature field contains the fixed text "EWM" followed by a null terminator to confirm the format of the file.
The oVersion field contains the version number of the file format. For all current files this is zero (0). Future upward compatible changes will increase this number by one for each format change. For incompatible changes the number will be increased to one hundred (100) or greater, so readers should check the version number and reject files with version numbers of 100 or greater.
The oDescriptorOffset field indicates the offset in bytes of the start of the descriptor data from the start of the file. The oDescriptorLength field indicates the length of the descriptor data in bytes.
Similarly, the oDataOffset and oDataLength fields indicate the offset and length of the map data.
The oTitle field contains the title or description of the map data. It contains up to MapFileTitleLength characters plus a null terminator.