John Yorks & Michael Williams
Millersville University of Pennsylvania
Table of Contents
2. Selecting Parameters (Data Selector)
4. Using the Parameter Window and Color Table Editor
"The Integrated Data Viewer (IDV) from Unidata is a Java™-based software framework for analyzing and visualizing geoscience data. This IDV release includes a software library and a reference application made from that software. The IDV "reference application" is a geoscience display and analysis software system with many of the standard data displays that other Unidata software (e.g. GEMPAK and McIDAS) provide. It brings together the ability to display and work with satellite imagery, gridded data (for example, numerical weather prediction model output), surface observations, balloon soundings, NWS WSR-88D Level II and Level III RADAR data, and NOAA National Profiler Network data, all within a unified interface. It also provides 3-D views of the earth system and allows users to interactively slice, dice, and probe the data, creating cross-sections, profiles, animations and value read-outs of multi-dimensional data sets. The IDV can display any Earth-located data if it is provided in a known format" (IDV Users Guide, Unidata).
In the data selector window click on FILE, NEW DATA SOURCE and 11 choices will appear. Clicking on any of these opens the Data Source Chooser window. This window is where the user will select the location of the data which they are displaying. The 11 options and the windows that appear when choosing each are listed and explained below:
Data Sources
a. From File System : The 'Files' option in the Data Source Selector allows the user to access any information or data that has been saved by either the user or another source that has granted the user prior access. For example, archived data could be stored here to be visualized using IDV. Any folders that have previously been loaded in or saved in the user's account can be viewed by clicking on the button to the right of LOOK IN. The data that is in the folder will be displayed in the window directly below. The user must click on the data which they want to view and click on ADD SOURCE located at the bottom of the page.
b. From a Web Server : This option allows for any URLs to be added that are not data locations already used by the IDV. URLs that the user knows to be sources of data that are compatible with the IDV software are excellent alternatives to data that the IDV automatically accesses. To add the web address, the user can type the entire address in the window marked URL and then clicks on ADD SOURCE. The URL is then added to the list of sources from which the user can access information and should appear in the DATA SOURCES window, which is the first white window on the left in the Data selector window. You can use OPeNDAP servers and dods://urls here. However, the novice IDV user will work mainly with URLs. When bringing in data from OPeNDAP servers and dods://urls, please refer to the IDV Users Guide.
c. From a Catalog : Many universities and government agencies run models on a regular basis (normally four times a day). This prediction data is then archived and made available to the general public through the web. Models that are available for viewing ( NAM , GFS, NGM, RUC, RUC2, SST, etc.) are listed in the large window below. At the top where it says ‘Catalogs' is the place from which the user chooses to access the model data. Generally the data is retrieved from the ‘Motherlode' server located at UCAR in Boulder, Colorado which is facilitated and maintained by Unidata. To select a model to explore the user must first expand the list of times. To do this, click on the circular blue button to the left of the chosen model. A list of run times will appear with the latest model run being first on the list. The user must click on the desired model and model run and then click on ADD SOURCE at the bottom of the window. The source is then added to the list of data sources in the Data Selector Window.
Data Types
d. Satellite Imagery : Choosing this option will allow the user to access global infrared, water vapor, or visible satellite images. The IDV is equipped with the capability to display satellite images while also overlaying other data. To select a satellite image the user first selects the server from which they wish to access. Next is the dataset from which the user wants to access. Generally RTIMAGES is the selection of most users. After choosing these options, click on the CONNECT button. Next is the IMAGE DATA TYPE, which allows the user to select from a number of options that displays the IR, Water Vapor and Visible in different fashions. After choosing the image data type, the user can then choose the times they want. After selecting all of this, the user can then click on ADD SOURCE at the bottom of the window. The source will then appear in the list of data sources in the Data Selector Window. Two specific image data types that are of interest to many IDV users are the ‘MDR Topo – Composite', which is a satellite composite of all of the radars around the nation coupled with Topography and state/country outlines, as well as the GOES East/West IR (or VIS) Topo – Composite, which allows the user to view large areas of the globe in terms of cloud cover.
e. Level III Radar : Here the user can select the server just as with Satellite Imagery. A map is available to make it easier to access an abundance of radar data from different locations in the country. There are buttons at the bottom of the map that make it easier to navigate the map to see the radar stations up close. The Declutter button on the left allows for radar stations to be sorted out so that there are only a few are left. This allows the user to easily see the three-letter abbreviations for each radar station. Below the user can select the Radar Data Type and choose from a list of available times. Like with most Data Sources, the user then clicks ADD SOURCE and the source appears in the list of sources in the Data Selector Window.
f. Level II Radar : To use this type of radar the user needs to first navigate the desired directory. This chooser works like any other file chooser. The user selects one or more Level II data files. Each file represents a full volume scan at a particular time. The user then provides a radar station name. For some Level II data IDV requires you to provide the radar location. IDV will try to guess the location based on the filename, but you can specify the location using the Radar Location menu. After completion, the user then hits ADD SOURCE to complete their choice. This type of radar is only useful if the user knows exactly the times and locations of radar data they need.
g. Observational Data : This allows the user to choose Surface Observations (METAR) and related data. Like before, the user selects the server and data type and clicks CONNECT. Then the user chooses the times that they desire. Then the user clicks on ADD SOURCE and the source is added.
h. Sounding Data- Remote/Sounding Data – Local/ Sounding Data – Single Level : These three options are all listed under RAOB, with separate tabs for each.
Remote : Select Server and CONNECT. Select times. Select station. Just as with radar, there are navigation buttons at the bottom of the map to help sort through the stations that exist throughout the world.
Local : With this option the user must choose their sounding from a file system rather than a server, but everything else is unchanged.
Single Level : Here the user chooses the server, data type and CONNECTS. Then the user selects the desired time, type of station model and pressure level they wish to view. Then the user selects ADD SOURCE.
i. Profiler Winds : The user must select a server and data interval and CONNECT. A map of available stations is provided with navigation buttons at the bottom. The user then chooses the time and clicks ADD SOURCE. This option gives the user a vertical profile of wind direction and speed at the location the user chooses.
Exercise-Part A .
II. Selecting Parameters (Data Selector)
After loading the IDV, two windows will appear on your screen. The first and larger of the two windows is the Data Display window. This window will display the information that is selected in the second window called the Data Selector window, which is shown below . This window allows the user access a host of different possibilities for displaying data. It is here that the user explores the numerous ways in which their data can appear.
a. Fields . In the center of the Data Selector Window is a smaller window named Fields. The options in this window change depending on what type of source the user has added. If the source is from a file system, a web server or a catalog, the fields will appear as 2D and 3D options. These options include but are not limited to; relative humidities at various pressure levels, temperatures at different pressure levels, winds at any level and in any direction, many types of vorticity, velocities, different instability parameters, dewpoints, mixing ratios, partial sounding data, flow vectors, thickness, etc. Any appropriate options can be chosen depending on how the user wants the data to be displayed. Satellite and Radar data will provide the user with field options dealing with the images themselves. The sounding data will provide simply the code for the station in the Fields window. The profiler data will list the name of the station in the Fields window.
b. Displays . The next option is the Displays option located in the right upper-hand corner of the Data Selector window. Here the user can control the appearance of the data that they have selected thus far. Below is a list of explanations to help guide the user with display options:
Plan Views :
1. Contour Plan View : This view allows the user to view a variable, such as temperature, pressure, etc. in a view where the changing values are contoured by an interval specified by the user. These intervals/contours usually change color from low values to high values, but the user can specify how they want the contours to look in terms of thickness and color of the lines.
2. Color-Filled Contour Plan View: This option is the same as the Contour Plan View with one difference, the space in between the contours is filled with a specific color. This option allows the user to view in greater detail where the temperature, pressure, etc. is changing (even in between the specified contours).
3. Color Shaded Plan View : This option is the same as the above option except the intervals are not contoured. The display will only show gradual transitions of coloras the variables change value rather than lines that show intervals of change.
Cross Sections :
1. Contour Vertical Cross Section : This cross section of a parameter in the vertical is the same as the horizontal Contour Plan View that was explained in the Plan View section. The specified variable is contoured according to changing values just as with the previous Plan View.
2. Color-Filled Contour Vertical Cross Section : This cross section is the same as the Color-Filled Contour Plan View that is explained above.
3. Color-Shaded Vertical Cross Section : This cross section is the same as the Color-Shaded Plan view that is explained above.
3D Surfaces :
1. Isosurface : An isosurface is a surface of some specified variable, such as a component of wind, which has the same value throughout. For example, the jet stream is not a flat river of air that simply changes speed, but rather a ‘tube' of air that contains changing speeds of air as you get close to the center of the ‘tube'. This 3D surface makes it easy for the user to see this wind speed change. After mastering the controls for the displays the user will also be able to construct multiple isosurfaces, while making some transparent, in order to view the changing winds within a jet streak.
Probes :
1. Probes allow the user to find the wind speed, pressure, temperature, etc. at any location in the field of view. However, the probe information is limited to the data that the user chooses to display on the IDV screen. For example, if the user displays a wind profile for winds that are 30 m/s and above, the probe can be moved through the map, both vertically and horizontally, to find exact wind speeds at certain pressure levels and heights. For Radar and Satellite selections the Displays window only gives the user the probe option.
Soundings :
1. The choice of RAOB data will bring up the soundings option in the Displays window. Three choices are under the ‘Soundings' heading. The user can choose which sounding they wish to view depending on their needs.
Profiler Winds :
1. In the displays window the user will see a Time/Height option, which allows for the user to load a number of times at numerous locations throughout the nation. A separate window will then appear showing the wind profile above that particular location.
c. Time . This window is used in almost every case when trying to view more than one specific time. The user has previously loaded in a list of times that they wish to use. This number may vary from one to perhaps as much as twenty. The more times that are used, the longer it will take for images to load once the display is created. There is a USE ALL box in the upper right corner of this window that is self explanatory. Deselecting this box allows the user to select specific times rather than using all of them. If the user only wants to use every other time they can hold down the CRTL key while selecting the times.
After completing all of these selections, the user will click on CREATE DISPLAY located at the bottom of the Data selector window and the data and specifications that the user has chosen will appear in the main IDV Data Display window. As aforementioned, depending on how much data is selected and how many times are chosen this may take up to a minute.
Exercise-Part B .
a. Side Legend . To the right of the IDV display is the Side Legend. This shows all of the displays present in the bundle. The parameter must be checked for it to be displayed. If the user does not want to view a certain parameter, the box has to be unchecked. Clicking on the parameter name in blue font will bring up the Parameter Window, while clicking on the color range will bring up the Color Table Editor.
b. Rotating . To rotate and move the display, hold down the right mouse button and drag the mouse. This is very useful for 3D displays as well as capturing pictures and movies. To return the image to the original position, press Control-R on your keyboard.
c. Time Loop . To put your bundle in motion using the different time images, press the play button on the Time Animation Controls. The user can also use these controls to go through the time images one by one.
Exercise-Part C .
IV. Using the Parameter Window and Color Table Editor
a. The Parameter Window allows the user to change settings such as; contour intervals, the level of a display, or the value of a surface. It also allows the user to change the color at the Color Table option, as well as change the label and display unit under the Edit Menu.
b. The Color Table Editor allows the user to change the color of the display, the values of the range of the color table, and the transparency of the display. Click APPLY to view your changes before saving them.
Exercise-Part D .
a. On the left side of the Display Window there are a variety of controls.
Starting at the top, there are boxes with one side shaded red. This is the Viewpoint Toolbar and these buttons allow the user to change the side of the box that the image is displayed on. Below these buttons is the Navigation Toolbar and these are used to zoom in and out. Below the zoom buttons are arrows which allow the user to move the image. A reset button is also here to allow the user to go back to the original view.
b. At the very top of the Display Window is your Main Menu Bar. Under the
File Menu you can load saved bundles, add new data sources, and save bundles. Under the Edit Menu the user can clear displays and data sources, as well as use certain formulas. The user can use the Displays menu to; load and save favorite bundles, change the background map, create a text note, use a range ring, or use a location indicator. The Data Menu lets you add new data sources and the Help Menu allows the user access to the IDV Users Guide.
c. The View Menus (lower toolbar) has 2 dropdown menus. The View Menu allows the user to remove displays, change color, change viewpoints, and capture pictures and movies. The projection window allows the user to set your projection to a regional view, a continental view, or a past view through the History option.
Exercise-Part E.
References
“IDV Users Guide.” 2005. Unidata Program Center/University Corporation for Atmospheric Research. Boulder, CO .