Icon Advanced usage

Mark level

The "mark level" is a specific tidal height or current velocity of your choosing. When you set a mark level for a location, the times at which the tide level crosses the mark level will be displayed at the bottom of graphs and included in plain listings and calendars. This option is useful to determine the times when the tide will be low enough to expose something that is submerged at high tide, or high enough to provide a desired depth. You can set a mark level by selecting the Set Mark option on the Options menu.

San Francisco graph with mark level

Note that mark level crossings will not be displayed in the clock window due to lack of space. Note also that some locations, namely subordinate stations with complex offsets, will not support setting a mark level for technical reasons.

Aspect

The "aspect" is a number that controls how stretched out or scrunched up a graph is. If timestamps are overlapping one another on a tide graph and becoming unreadable, you can increase the aspect to make them farther apart. An aspect of 1.0 is "normal;" an aspect of 2.0 stretches the graph by a factor of 2; an aspect of 0.5 does the opposite, compressing the graph. You can change the aspect by selecting the Set Aspect option on the Options menu.

Portland, England at aspect 1.0

An indecisive low tide at Portland, England has obscured the timestamps in this tide graph.



Portland, England at aspect 4.0

Stretching the graph to aspect 4.0 clears up the mystery.



Washington, D.C. at aspect 0.5

This tide clock has been compressed to aspect 0.5.



The control panel

The control panel is the easiest way to customize the many user-serviceable settings of XTide. It's not pretty, but it gets the job done.

XTide control panel

Colors can be changed to any of the "standard" X-windows color names or to 24-bit RGB specifications of the form rgb:hh/hh/hh by typing the new colors in the dialog boxes. Other settings have pull-down choice menus or counting buttons to help you along. Least user-friendly, but most powerful, are the timestamp formats. In return for reading the Unix man page for the strftime library function, you are empowered to change the timestamp formats to practically anything you could ever need.

You can choose Apply to see how the settings look in the current session only, or Save to make the settings permanent. They will be saved in the file ~/.xtide.xml.

The following is one example of the sort of thing you can accomplish using the control panel. "Draw tide graphs as line graphs" was selected, and the timestamp formats were changed to use 24-hour time instead of AM/PM. (The format strings for this are provided in the on-line help for the control panel.)

Line graph with 24-hour timestamps

Command line options

The interactive client supports all of the command line switches related to settings which are described in a later section. In addition, it supports the following.

-b "YYYY-MM-DD HH:MM"
With -l, specify the begin (start) time for predictions using the ISO 8601 compliant format shown above. The timestamp is in the local time zone for the location, or in UTC if the -z setting is engaged. If no -b is supplied, the current time will be used.
-display "X display"
Specify the X display, e.g. "quake:0.0". This overrides the DISPLAY environment variable.
-fn "font"
Specify the font to use for text windows, buttons, and labels. This will not affect the font used in tide graphs and other cramped spaces, which is not a user-selectable parameter.
-l "Location Name"
Specify a location for tide predictions. When given to the interactive client, this causes it to start a tide clock for the specified location instead of launching a location chooser on startup. This is useful for starting a tide clock automatically when you log on. Multiple uses of -l will result in multiple tide clocks. The -m switch can be used to choose graph or plain mode instead of clock mode, and the -b switch is effective in these cases. (Please read Important note about the -l switch.)
-m g|p
With -l, specify mode to be graph or plain instead of clock.
-v
Print version string and exit. Please note that versions marked as DEVELOPMENT versions are not really versioned; they are work in progress and will change without warning.