1. Create an isosurface of wind speed showing areas of winds 40 m/s or greater.
   • In the Field Selector's Data Sources panel, select the NCEP Model Data ETA data source that you loaded at the start of this section.
   • In the Fields panel, expand the 3D grid tab. Scroll down to the Derived tab to see a list of derived quantities. Select the Speed (from GridRelative_u & GridRelative_v) field.
   • In the Displays panel, expand the 3D Surface tab and select Isosurface, then click the Create Display button.
   • Set the isosurface to display where winds of 40 m/s or greater exist. From the control window for this display, you can change the isosurface value either by typing a new value in the Isosurface Value entry box or by using the Isosurface Value slider widget () to the right of the entry box. Change the isosurface value to 40 m/s.
   • Start the animation.
   • Rotate the display to see the wind speed pods from various angles.
   • Stop the animation and return the display back to the first time in the sequence and the view to the top.
   • Remove the display from the main window by clicking on the remove icon () or by selecting the control's File→Remove Display menu.
2. You can also create isosurfaces of one variable that is colored by another variable. In this step, you will load in an isosurface of wind speed again, but this time you will have it colored by geopotential height.
   • In the Fields panel, expand the 3D grid tab. Scroll down to the Derived tab to see a list of derived quantities. Select the Speed (from GridRelative_u & GridRelative_v) field.
   • In the Displays panel, expand the 3D Surface tab and select Isosurface colored by another parameter then click the Create Display button. (you may have to scroll the Displays pane to find the display selection)
   • After you click the Create Display button, a dialog will pop up to allow you to select the Other parameter. From the dialog, expand the 3D grid node and select the geopotential height field and click the OK button.
   • Adjust the wind speed value to 40 m/s.
   • Start the animation.
   • Rotate the display to see the wind speed pods from various angles.
   
   
   • Stop the animation and return the display back to the first time in the sequence and the view to the top.
3. You can modify the colors the display through the menus in the control window or legend.
   • You can use a different color table to show the variation of windspeed with altitude. Click on the default button next to the Color table label in the control window to bring up a list of pre-defined color tables. Select the Basic menu and choose the Bright38 menu item to change to that color table. In a later exercise, you will learn how to create and modify your own color tables.
   • Rotate the display so you are looking at the view from the south. On the first time-step, the pod of 40 m/s winds bulges down into the blues of the color table. Place your cursor at the bottom of this bulge and note the Altitude readout at the bottom of the main window. It should read about 5000 m.
   • Now move your cursor over the color bar in the legend to the point where the color at the bottom of the bulge is. Notice that the readout on the color bar is about 5000 m as well.
   • Start the animation.
   • Rotate the display to see the wind speed pods from various angles.
   • Stop the animation and return the display back to the first time in the sequence.

Unidata IDV Workshop for version 6.3 > Accessing and Displaying Data > Working with Gridded Data