Garmin GPSMAP 640 Manual

Also see for GPSMAP 640: Quick reference guide Declaration of conformity Installation instructions Quick reference guide Owner's manual

Contents

6 GPSMAP 640 XM WX Satellite Weather and XM Satellite Radio SupplementMarine Mode: Using XM WX Weather and AudioViewing Forecast Sea Conditions information for anotherTime Period1. From the Home screen, select Weather > Sea Conditions.2. Complete an action:• Select Next Forecast to view the forecast visibility for the next12 hours, and select Next Forecast again to view forecasts for thenext 24 and 36 hours, in 12-hour increments.• Select Previous Forecast to view the forecast visibility for theprevious 12 hours, and select Previous Forecast again to viewforecasts for the previous 24 and 36 hours, in 12-hour increments.Viewing Fishing informationThe Fishing screen shows present water temperature, present surfacepressure conditions, and fishing forecasts.From the Home screen, select Weather > Fishing.Surface Pressure and Water Temperature DataSurface-pressure information appears using pressure isobars and pressurecenters. Isobars ➊ connect points of equal pressure. Pressure readingscan help to determine weather and wind conditions. High-pressureareas are generally associated with fair weather. Low-pressure areas aregenerally associated with clouds and the chance of precipitation. Isobarspacked closely together show a strong pressure gradient. Strong pressuregradients are associated with areas of stronger winds.➋➊➌Pressure units are shown in millibars (mb), inches of Mercury (inHg), orhectopascals (hPa).Colored shading ➋, as defined by the legend ➌ in the upper-left corner ofthe display, indicates the surface temperature of the water.