HdfExplorer reads HDF files. To open a file just choose the File Open command menu. After the file is opened, the kind of data it contains is shown in the form of tree items, using the Microsoft Windows tree control. Each kind of HDF data has its own associated icon.
In this example a file called test.hdf was opened. Each HDF file is placed under a root item with the name of the file.
To browse the HDF file just click on the expandable tree item. The tree will show the corresponding sub-items. In this example a SDS item was expanded to show the SDS
atributes.
To visualize your data click with the mouse right-button on the selected tree item. A menu will appear that lists the kind of views available for that HDF data type. The HDF data format can store images, text, and numeric arrays. HdfExplorer shows each data object accordingly. There are mainly two types of views in HdfExplorer: a grid view, where the numbers are displayed in a rectangular grid of values, and image views, where the numbers are translated into a map of colors. For the SDS data object a third kind of view is available, the vector view.
After the view is opened the tree contents of the selected item turn to a bold face. When the view is closed the tree contents revert to the normal face.
The SDS data type has four kinds of associated views.
In the grid view the SDS is showed as a grid of numbers. The grid origin is placed in the top left corner of the grid.
In the discrete map view the SDS is visualized as a map of colors. The colors are associated with a discrete range of values.
In the continuous map view the SDS is visualized as a map of colors. The colors are associated with a continuous range of values.
In the vector view the two SDS are visualized as a vector field.
To view each tree item HDF properties just click with the mouse right button on the selected tree item and choose the properties menu.
The properties window shows some features of the HDF object, like its reference number, its number type or its dimensions. Addicional information on these properties can be found on the NCSA HDF userīs guide.
The dump window lets you analyse the HDF contents by tag and reference. Just click with the mouse right button on the root tree item and choose the dump menu.
The HDF tag and reference numbers are displayed in a grid. Addicional information on the tag and reference properties of the HDF file can be found on the NCSA HDF userīs guide.
The SDS scalar object in a HDF file can be visualized as a map of colors. The user has some control on the appearence of the map, like changing the legend values, choosing another font or palette. All options are available on the Options menu item.
In the Draw options dialog box the user can choose to draw the color of each cell and to draw a grid surrounding each cell.
When this option is enabled each cell is surrounded by a rectangle. This option is useful to visualize grids with variable dimensions.
In the Fill options dialog box the user can choose to ignore or not a SDS fill value. If a SDS contains a fill value, by default HdfExplorer ignores this value in the making of the map, that is, the fill value is not translated to a color. The user also has an option to draw the fill value border in the grid.
In this example (salinity map of the Mediterranean Sea), a fill value was assigned to the land values.
In the Dimensions options dialog box the user can choose to visualize or not the SDS dimensions in the map. It is also possible to invert the heigth scale. By default the height origin is placed in the bottom left corner of the map.
In the Axis options dialog box the user can choose to visualize the space legend in the map.
In the Size options dialog box it is possible to change the size of the image.
In the Legend options dialog box it is possible to change the values of the legend. To change a value, click on the color, and the enter the new value in the input box. This option is only available for the SDS discrete map view.
To select another palette into the map choose the Options Palette menu item. HdfExplorer has two built in palettes, but it is possible to load a palette from a file (PAL files), which is a standard format in the Microsoft Windows environment.
The PAL format stores the RGB values of the palette in ASCII file. An example of the format of the file is
CWPAL File ident string
100 version number
256 number of colors N
0 0 0 Array of RGB Nvalues
128 0 0
0 128 0
...........
To select another font into the map choose the Options Font menu item.
If the HDF file contains two datasets of the same size, it is possible to generate a vector field with these two sets. Typically these two data sets contains two velocity components.
To visualize your data as a vector field:
First, select the vector view menu option. Note that this option is only enabled when the HDF file contains two or more data sets with the same dimension.
Tip: Select the tree item that has the horizontal component of the velocity.
Now, you must choose the two velocity components. Just click on the listed SDS on the dialog and press Ok.
The SDS map vector options are similar to the SDS scalar map options. There is one aditional dialog option for the vector field and the Draw option has some extra features.
The vector options dialog box lets you choose the scale of the vectors, to define a value for the legend, and to choose the space between grid cells that each vector is drawn.
The Draw options of the vector view are similar to the scalar view. The user can choose to draw some basic features of the map. These are the arrow representing the vector, the rectangular grid, and the magnitude of each vector as a color. It is also possible to invert this palette.
The layer toobar lets you browse between layers on a SDS 3D data set or GR multi component image.
The current layer and the number of layers is written on the Hdf Explorer status bar.
 |
Goes to the next layer |
 |
Goes to the previous layer |
 |
Goes to the last layer |
 |
Goes to the first layer |
The image data can be exported to the Windows clipboard either as metafile or bitmap format. The metafile format is desirable for printing in good quality laser printers. The grid view data and attributes are exported as ASCII text.
HDF Explorer also includes an export facility that saves your images in the Windows Bitmap format (BMP).
Each HDF data object has one or several HdfExplorer associated icons. These icons are displayed in the data window as part of the tree items.
Addicional information on the HDF data objects can be found on the NCSA HDF user's guide.
The SDS data model has seven associated icons
One
dimensional data set
Two
dimensional data set
Three dimensional data set
Attribute
Numerical attribute
Pre-defined attribute
Pre-defined numerical
attribute
The RIS8 data model has two associated icons
RIS8 image
Palette
The RIS24 data model has one associated icon
RIS24 image
The GR data model has seven associated icons
One layer GR image
Multi layer GR image
Palette
Attribute
Numerical attribute
Pre-defined attribute
Pre-defined numerical
attribute
The Palette data model has one associated icon
Palette
The AN data model has one associated icon
Annotation
The Vdata data model has one associated icon
Vdata
The Vgroup data model has one associated icon
Vgroup
This section lists all the HDF Explorer icons associated with the HDF data objects
One
dimensional data set
Two
dimensional data set
Three dimensional data set
Attribute
Numerical attribute
Pre-defined attribute
Pre-defined numerical
attribute
RIS8 image
Palette
RIS24 image
One layer GR image
Multi layer GR image
Annotation
Vdata
Vgroup
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