Coordinate Files

 Certain applications read text files which contain a list of coordinate positions (either sky or image coordinates). By default, these files are assumed to contain image coordinates. This assumption may be over-riden by inserting a line at the start of the file which specifies the sky coordinate system. This must be a valid sky coordinate system specification (see section ). It is not necessary to specify a coordinate system if the coordinates in the file are image coordinates (also known as pixel coordinates). The remaining items in the file must be coordinates specifying the positions to be transformed. The two coordinate values describing a single position should occur together in the order X then Y or longitude then latitude. Image coordinates are given as simple decimal values, and the formats allowed for sky coordinates are described in section . Adjacent items in the file should be separated with commas or by placing them on separate lines. Text occurring after a comment character (``#'') is ignored (up to the end of the line). Blank lines are also ignored.