Winds Tab - Revision history

Omar: /* Methods */

2015-02-05T20:33:10Z

‎Methods

2014-11-22T12:04:17Z

‎In Practice

2014-10-14T00:17:53Z

‎Some Examples

2014-10-08T05:58:39Z

‎In Practice

2014-10-08T05:55:14Z

‎U/V Interpolation

2014-10-08T05:43:27Z

‎In Practice

2014-10-08T05:39:42Z

‎Some Examples

2014-10-08T05:31:29Z

‎Some Examples

2014-10-07T05:42:34Z

‎Methods

2014-10-07T05:38:58Z

‎In Practice

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 <br style="clear: both" />
-===Methods===
+===Interpolation Methods===
 These are some of the methods of wind interpolation you can use:

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 ===In Practice===
-[[File:ChartWindInterpolation.gif|right]]Once you have some weather loaded, you can easily see interpolation working by selecting the '''Ruler''' [[File:ToolbarRuler.gif]], '''Route''' [[File:ToolbarRoute.gif]], or '''Track''' [[File:ToolbarTracks.gif]] tool and moving it over the chart. The wind indicated by the tool will match the ''grib'' values displayed at the ''grib'' ordinates, but vary gradually as you move the tool between the ordinates.
+[[File:ChartWindInterpolation.gif|right]]Once you have some weather loaded, you can easily see interpolation working by selecting the '''Ruler''' [[File:ToolbarRuler.gif]], '''Route''' [[File:ToolbarRoute.gif]], or '''Track''' [[File:ToolbarTracks.gif]] tool and moving it over the chart. When the tool is at a ''grib'' ordinate the wind indicated by the tool will match the value displayed on the chart; as you move the tool away from a ''grib'' ordinate the wind displayed by the tool will change gradually to an interpolated value.
 For '''games''', you can check that your wind interpolation settings are correct:

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 '''Most current games''', such as Virtual Regatta games:
 *Check the [[File:CtrlCheck.gif]]'''Interpolate winds''' checkbox<br>
-*Set interpolation in '''time''' to [[File:CtrlOption.gif]]'''previous'''<br>
+*Set interpolation in '''time''' to [[File:CtrlOption.gif]]'''previous''' (meaning there is '''no''' temporal interpolation)<br>
 *Set interpolation in '''position''' to [[File:CtrlOption.gif]]'''bilinear'''<br>
 *Check the [[File:CtrlCheck.gif]]'''Use U/V interpolation for TWD''' checkbox<br>

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 For '''games''', you can check that your wind interpolation settings are correct:
-#First make sure you are looking at the '''current weather''' in both VRTool and in the game console. Now compare the wind speed and direction '''at the ''grib'' ordinates'''. To do this in the game console you need to zoom right in and place the cursor precisely on the ''grib'' ordinate.  If they match closely then you have verified that VRTool has the correct ''grib''.
+#Make sure you are looking at the '''current weather''' in both VRTool and in the game console.
 #Now compare the speed and direction at a selected intermediate point away from the ''grib'' ordinates. If these don't match then one of the wind interpolation settings is wrong. If the speed matches closely but not the direction then change the '''U/V Interpolation for TWD''' setting.

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 Currently (as of 2014) the '''Virtual Regatta''' games use these same methods to apply wind interpolation.
-You can set VRTool to use u/v interpolation for wind direction by checking the '''[x] Use U/V Interpolation for TWD''' checkbox.
+You can set VRTool to use u/v interpolation for wind direction by checking the [[File:CtrlCheck.gif]]'''Use U/V Interpolation for TWD''' checkbox.
 U/V interpolation of wind direction has a pronounced effect when you are close to a coastline and one or more of the surrounding ''grib'' ordinates is on land. In the open sea it makes very little difference.

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 '''Real World''' modelling at sea:
 *Check the [[File:CtrlCheck.gif]]'''Interpolate winds''' checkbox<br>
-*Select interpolation in '''time=linear''' and '''position=bicubic'''<br>
+*Set interpolation in '''time''' to [[File:CtrlOption.gif]]'''linear'''<br>
 *Check the [[File:CtrlCheck.gif]]'''Use U/V interpolation for TWD''' checkbox<br>
 The simulated wind will vary constantly with both position and time (as it does in nature).
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 '''Most current games''', such as Virtual Regatta games:
 *Check the [[File:CtrlCheck.gif]]'''Interpolate winds''' checkbox<br>
-*Select interpolation in '''time=previous''' and '''position=bilinear'''<br>
+*Set interpolation in '''time''' to [[File:CtrlOption.gif]]'''previous'''<br>
 *Check the [[File:CtrlCheck.gif]]'''Use U/V interpolation for TWD''' checkbox<br>
 The simulated wind changes as you change position, but at any one position it remains fixed for the duration of the forecast period.

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 [[file:InterpTypes.jpg‎]]<br>
 ''Interpolation methods''
 In the '''real world''' the weather changes constantly in both time and position, so for use on board at sea you will get the most accurate simulation by interpolating in both time and position.

← Older revision		Revision as of 05:38, 7 October 2014
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	A simple consequence of interpolated wind is that if you set your boat to sail with a constant true wind angle (TWA) it will sail along a '''curved''' track, due to the constantly changing wind direction.		A simple consequence of interpolated wind is that if you set your boat to sail with a constant true wind angle (TWA) it will sail along a '''curved''' track, due to the constantly changing wind direction.
		+	<br style="clear: both" />

	===Some Examples===		===Some Examples===