Ralph E. Taggart WB8DQT

The interface unit described in the 5th Edition of the Weather Satellite Handbook was designed to provide images of extremely high quality. The unit digitizes incoming video to 256 grayscale steps per pixel and can sample 4096 pixels per second with any A/D chip or up to 8192 pixels per second with a slightly faster A/D. In effect, it was designed as a no-compromise approach to interfacing weather satellite video to a computer.

The 5th edition did compromise when it came to software. The software (WSHFax Ver. 1.5) was designed to be used with any PC that had at- least a standard VGA card. The software was configured to deliver a 512 x 480 pixel display with 16 grayscale steps per pixel - the best display possible for a standard VGA card. The image processing routines built into the Ver. 1.5 program were included to make the best of the 16 step video and the resulting pictures are just fine for many users, especially those that have to use a somewhat old-fashioned PC.

Shown here is a 300 x 300 pixel subset of a full-frame METEOR 3.5 image, displayed using the WSHFax 1.5 software and the WSH Interface. The PCX image save function was used to capture the image from the VGA screen. When viewed full-frame the picture looks pretty good, but if you "zoom" in, the pixel structure starts to become very evident, since there are really only 16 possible shades per pixel. The limitation here isn't the interface, it is the software used with the interface!

There are many advantages to using an older computer to acquire images, since you can often get them at very low cost (or even nothing), making it practical to dedicate the computer to acquiring images without having to interrupt activities on your main computer system. However, it would be nice if the images looked better when you used the "big" computer to view them. Here is where WSHFax Ver. 3.0 comes in:

This is a RESURS-01N image, essentially identical in format to METEOR 3.5 and the image here is also a 300 x 300 pixel sub-set of the full frame. You don't have to be an expert to see that this image looks a lot better with the Version 2.0 software than a comparable image using Version 1.5 - even though the same interface was used for both images! The reason is simple. 3.0 displays the image at the same standard 512 x 480 VGA resolution (16 grayscale steps), but the image is stored in RAM with 256 grayscale coding. The new software has a routine to save the RAM version of the image at 256 grayscale quality using the Windows-standard .BMP bit-map image format. The program does not include all the elaborate image processing functions because it is expected that you will periodically transfer the image to a more capable machine for archiving. If you do, the 256-step grayscale can be displayed in all its splendor using any Windows graphics program. What's more, the graphics program will give you a much wider and more precise range of image processing options. In effect, Version 3.0 takes advantage of all the grayscale capabilities originally designed into the interface.

A Beta version of 3.0 is posted on this system and can be downloaded by anyone with the WSH Interface. If you have experience with Version 1.5, running 3.0 will present no challenge. The pictures will look the same (assuming no processing) on the standard VGA screen, but you will see the difference when you transfer the .BMP image files to a more graphics-capable system.

Future software will upgrade the capabilities still further, taking maximum advantage of the high-resolution capabilities of the interface. If you have built or are going to build the WSH Interface, be assured that it can deliver APT pictures equal to the most elaborate (and expensive) interface options out there! Stay tuned for future developments....