一种提高电子海图上船舶航迹显示速度的方法

在电子海图上叠加显示船舶运动轨迹对船舶航迹分析和海上事故回放具有重要意义.船舶AIS(Automatic Identification System)报文提供了一种新的船舶动态和船舶运动轨迹获取方式.由于有关船舶动态的AIS报文发送频度较高,致使船舶运动轨迹点较为密集,这种情况将会导致电子海图系统在显示较长时间段船舶运动轨迹时,速度下降,从而降低了系统的用户友好性.利用垂距法对船舶动态数据按照电子海图显示比例尺进行分层.当电子海图显示比例尺较小时,仅显示船舶运动轨迹轮廓,而当显示比例尺逐渐增大时,显示海图显示地理范围内更详细的船舶运动轨迹信息.实验表明该方法能有效地提高船舶运动轨迹的显示速度.

A Method to Speed Displaying Ship Track on Electronic Chart

It's of great value to overlay ship motion trajectories on electronic chart for voyage analysis or marine accident replaying. Ship borne AIS transmit position reports in short interval , as a result, the plotting dots of ship trajectories may be very dense. It will occupy a lot of time to overlay ship trajectories, especially long ship motion trajectory, so as to decrease the display speed of system on electronic chart significantly. By using perpendicular distance method, a classical vector data compression method, the ship positions data can be split into different display layers according to chart range scales; when the chart scale is small, only contour line of trajectory is displayed on electronic chart; when the chart scale is getting larger, more detailed trajectory information is displayed in current geographical window; when the chart scale reaches to a certain level, all trajectory information is displayed. Experiments show the proposed method can speed the display of ship motion trajectory on electronic chart notably.