gmt-fork/doc/rst/source/explain_-D_cap.rst_

**-D**\ [**+x**\ *xname*][**+y**\ *yname*][**+z**\ *zname*][**+s**\ *scale*][**+o**\ *offset*][**+n**\ *invalid*][**+t**\ *title*][**+r**\ *remark*]
    Give one or more combinations for values *xname*, *yname*, *zname* (give the names of those variables
    and in square bracket their units, e.g., "distance [km]"), *scale* (to multiply grid values after
    read [normally 1]), *offset* (to add to grid after scaling [normally 0]),
    *invalid* (a value to represent missing data [NaN]), *title* (anything you
    like), and *remark* (anything you like). Items not listed will remain untouched.
    Give a blank name to completely reset a particular string.
    Use quotes to group texts with more than one word.  If any of your text contains plus symbols
    you need to escape them (place a backslash before each plus-sign) so they are not confused with the
    option modifiers.  Alternatively, you can place the entire double-quoted string inside single
    quotes.  If you have shell variables that contain plus symbols you cannot use single quotes but
    you can escape the plus symbols in a variable using constructs like ${variable/+/\\+}.
    Note that for geographic grids (**-fg**) *xname* and *yname* are set automatically.