SINKCHART — Definition from Imperial Archives, Commentary from Count Fenring

Definition: map of the Arrakis surface laid out with reference to the most reliable paracompass routes between places of refuge. (See Paracompass.)
Commentary: Detailed maps of the Deep Desert are impossible to create due to the guild prohibition on satellites and the constant storms which alter the landscape. A survey probe can be used to map local terrain, and create a sinkchart for distribution. Be wary though, sinkcharts are quickly out of date.