THE
BROAD
WAY
| A Pennsylvania Railroad Home Page
PRR INTERLOCKING
DIAGRAMS
| RELEASE NOTES | |||
|
THE
BROAD
WAY
| A Pennsylvania Railroad Home Page
PRR INTERLOCKING
DIAGRAMS
| RELEASE NOTES | |||
Color resolution. All maps are scanned into a 2-color format, i.e. black/white, at several contrast (threshold settings).
Image resolution. Most maps are scanned at 200 dpi (dots per inch). Most are just over 1000 pixels (dots) wide (high). Length varies considerably, with certain maps being folded, often multiple times, to fit within a given size for the 'book'. The exception to the 200 dpi rule is John Cooper's original scans, most of which were done at at 150 dpi; yet even here, ZOO interlocking was done in parts at 300 dpi and as a single sheet at 150 dpi.
Image information. The web pages contain the following image information: length and height in pixels; file size in KB; and scanning resolution in dpi.
Division into parts. Those maps which cause problems with Internet browsers have been cut, manually, into two or more parts. These parts overlap slightly for clarity. The entire map is available as well for downloading and printing. Good image processing programs (Lview, Corel Photo-paint, Adobe Photoshop) will handle the large images even when your browser will not. Color depth. Diagrams were inverted to black on white where needed. I have not yet found an interlocking diagram that has demonstrated a need for shades of gray -- if anyone wants to dispute this, I am happy to entertain other opinions. The second reason for such thresholding is that the resulting file sizes are much smaller. The blueprints were generally white on blue, though some were blue on white or black on white. All were converted to black on white, as the color is not significant. Black on white also decrease users' (over)usage of laser printer toner. The actual appearance of the original is listed in the References page. Need for editing.
Why is editing necessary, and why is the original not "good enough"? The original may not initially be thought of as a grey-scale (or blue-scale) image, but it is. The variation in degree of blue occasionally helps one interpret what the diagram should show had its reproduction from the original vellum been perfect and had the diagram never been worn, rubbed, etc. by human hands in the field. Some things that are easily interpreted with this variation in the blue color cannot be understood when the image is thresholded to black and white. At any rate, there are several competing issues involved here; "just scan it" or "the original scan is the (only) correct scan" is really much too simplistic a viewpoint. Accuracy.
Every effort has been made to maintain the accuracy of the diagrams through the scanning and editing process. Although I believe them to be accurate, it is not impossible for errors to have been introduced. The source material was itself not always entirely clear, and I do not have access to all available source material. I and my co-editors are always willing to make corrections providing that sufficient and appropriate documentation is given, and anyone finding any error is asked and encouraged to write to me to effect such change. I am also happy to forward to the owners of the source material any questions or comments anyone may have regarding the veracity of this material.
The best solution by far is to use a sophisticated imaging program, such as the products from Corel or Adobe, or page layout programs from Adobe or Ventura. These programs can rotate the image to print "landscape", printing as much as will fit on a page, and print as many pages as needed to print the entire image. If you don't have these at home and don't wish to spend the (considerable) sums of cash to get them, put the map on a floppy disk and go to your local Kinko's, or equivalent, and use a computer there.
Lview prints acceptably those maps that can be read when shrunk to the size of a single page. The Windows 3.1 paint applet will print the image out on as many sheets of paper needed to represent it; too bad it uses so many dots on the page to represent each pixel: the applet seems to be designed for 150 dots per inch printers.
Mark D. Bej