Browsing the GOES Image Archive

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Introduction

The GOES Image Archives (http://www.goes.noaa.gov/srcheast2.html and http://www.goes.noaa.gov/srchwest2.html) provide access to over 26,000 GOES images selected based on region, band, and time. This archive can be thought of as a three dimensional cube of images with region as the x-axis, band as the y-axis, and time as the z-axis (See Figure 1).
Figure 1
Figure 1
This sort of image cube is actually very common for multi-dimensional gridded datasets and model results generated by NOAA. Being able to visualize such image collections on the web is, therefore, an important goal for NOAA.


At present there are two web sites for visualizing the GOES images. The Geostationary Satellite Server (http://www.goes.noaa.gov) serves the most recent images, the slice on the front of the cube in Figure 1. These images are presented using a table that looks very much like the front of the cube (Figure 2).
Figure 2
Figure 2
Users can see larger versions of any single image by clicking on one of the thumbnails in the table. The GOES Image Archives (http://www.goes.noaa.gov/srcheast2.html and http://www.goes.noaa.gov/srchwest2.html) provide interfaces that include select boxes for specifying the parameters of the desired image and, again, any single image can be viewed
Figure 3
Figure 3
. Both of these selection and visualization approaches lead the user to a single one of the 26,000+ images in the archive (heavy outlines in Figure 1). This provides access to the images, but makes it difficult to compare multiple images.

We have developed a technique that allows users to visualize any planar subset of the archive cube (like the shaded planes in Figure 1). This approach is termed the Web Image Slide Tray (WIST). A WIST represents the two dimensions as rows (y) and columns (x) in a table and the third dimension as a "legend" dimension (z) that applies to the entire table. The user can use the controls in the upper left corner of the WIST to select the axes to be displayed and how many images to display along each axis. Dealing with the options that this provides is really quite interesting and can be a little mind boggling. The initial display shows a series of regions and bands for the same time (date is the legend dimension). This is the same as the initial view on the Recent GOES Server (Figure 2), but the rows and columns are transposed.

We believe that this approach provides a powerful tool for utilizing the already existing GOES image archive. It is implemented as a custom tag library in Java Server Pages (see http://www.ngdc.noaa.gov/wist/ for other examples and sample jsp code) so it is very lightweight. Note that the WIST can be implemented on any server (as in this case it is implemented in Boulder), because the WIST just constructs the HTML and the client retrieves the images.

GOES WISTS

The GOES archive has three dimensions that define a particular image: Region, Time, and Band (Figure 1). Presenting all of these dimensions simultaneously can be confusing for novice users or superfluous for simple applications. The GOES WISTs demonstrate the WIST concept as well as how the WIST framework can support a variety of interfaces into a 3-dimensional archive.

What is Happening in the Atlantic Hurricane Region?

GOES images provide a great resource for users interested in Hurricanes and other storms in the Atlantic. These users want to see recent activity in a single region. This is a vertical slice parallel to the sides of the cube in Figure 1 (shown in red). The Atlantic Hurricanes (Simple) WIST addresses this need. It allows users to select a day of a week and the band and then displays images for six times.

This example demonstrates some WIST concepts. This WIST contains two dimensions: time and band. The time dimension has two elements: Date and Time. Date is a legend dimension, it appears in the upper left hand cell of the WIST and applies to all cells in the WIST. Time is a row dimension, it can have a different value for each row of the WIST and applies to all cells in a row. This simple WIST shows only six times, selected to avoid night time in this region. If users need to see more times, there is a link at the bottom of the page to the Atlantic Hurricanes (More Times) WIST that includes all possible times.


Dimension Choices
Region Set to Atlantic Hurricane
Time Date selectable using day of the week, only a subset of the possible time values are available (selected to avoid dark night time images in the visible band).
Band Selectable (IR set as initial band because it has data at night)

This WIST also includes a sizemap that maps a set of descriptive words (Thumbnail, Small, Mediuum, and Large) to a set of image dimensions. This allows users to select an image size that works for their display. Note that each image also links to the original at its native location and size.

What is Happening in the Pacific Storm Region?

The Pacific Storms WIST serves the same purpose as the Atlantic WIST discussed above, but it covers the Pacific Storm region. This could be offered as a legend selection on the Atlantic WISTs, but it is not in order to keep the simple interfaces.

Recent GOES Images

The WISTs described above simplified the interface by picking constant regions. Another simplification is to show only one time, like the blue plane in Figure 1. The Recent GOES Images shows only the most recent GOES images.

This WIST introduces some significant capabilities at the prices of a more complex user interface. The WIST exposes two dimensions: Band and Region and allows the user to select the axis that these dimensions are associated with. In the initial state, Region is a row dimension and 3 of 5 rows are displayed. Band is a column dimension and all 3 columns are displayed.

The associations between the axis and the dimensions and the number of rows and/or columns can be manipulated by the user to create a display that matches their needs. For example, if a user wanted to see all regions, they could set the number of rows to 5 (the maximum) and refresh the WIST. If a user was on a laptop with a narrow screen, they could set the number of columns to 1 and then the select box on the top of the column would allow them to select the band. To see all of the bands for a single region, the axis selector could be set to Rows for Band and Columns for Region.

The Full Monty

The WISTs described above were designed to address specific needs with simple interfaces. Hopefully those will cover the needs of a many users. However, some users will undoubtedly want access to the entire GOES Archive.

This WIST exposes the full interface to all dimensions of the GOES Archive: Date/Time, Region, and Band. It also allows full flexibility in associating those dimensions with axis of the display.


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