Q: What is the meaning of DM, HDG and DP abbreviations used in Onshore webUI?
A: DM is the mean wave direction (traveling towards).
HDG is buoy mean heading
DP is wave peak direction. DP is the direction of the waves (traveling towards) in the peak period (with highest energy).
Since waves are not perfectly identical there will be periods with smaller and larger waves/periods and not necessarily in the same direction, some arise from local winds, others from dominant weather systems etc. for a given time there is the mean direction of all the waves and a direction for the peak waves (with higher energy).
The buoy calculates the wave data based on the document referred to in the ToughBoy manual: http://www.ndbc.noaa.gov/wavemeas.pdf