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.
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.
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.
An indecisive low tide at Portland, England has obscured the timestamps in this tide graph.
Stretching the graph to aspect 4.0 clears up the mystery.
This tide clock has been compressed to aspect 0.5.
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.
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.)
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.