Added August 13 2009.
Converts and scales between foot / inch, and meter / centimeter / millimeter type lengths. Also helps with getting scale lengths from images.
You may need to click twice at first, or if you moved your mouse pointer off of the tool. Once to set focus on the tool and the next to select a choice.
Select scale and input / output types.
You may enter both a large and small dimension (ex: feet and inches) or just one. Changing the input type will clear the input boxes so select the type before adding dimensions.
"Add Label To Result" is optional and will prefix the result with whatever you enter. Use labels to keep track of multiple scaled dimensions.
Use the 1/1 scale for straight standard / metric conversions.
Results are limited to 100, after which the "CLEAR ALL" button must be pushed.
To copy results, click on results box, right-click and choose "select all", then right-click and choose "copy". Or click on results box then use keyboard shortcuts (usually ctrl/a - ctrl/c) to select all then copy.
Option "Clear On Click" will clear the dimension or pixels, and label boxes when clicked on again, as long as they are not still active.
Option "Clear On Result" will clear the dimension or pixels, and label boxes when a result is added.
Option "Plain Output" will give a short result of the label (if entered) and the scaled length.
Option "Reverse Scale" will scale the results up by the selected scale.
Button "Add Result" will add the conversion results to the results panel.
Button "Clear Inputs" clears the dimension(s) and label boxes. Scale will be kept.
Button "CLEAR ALL" will also clear the results box. Scale will be kept.
Button "Help" shows this text.
The "Pixels" input option is used on the orthographic type drawings (no perspective warp) found on this website, and when the only dimensional reference available is a photograph. You must know the dimension of at least part of the image to use this method. Accuracy when used on orthographic drawings is good.
Accuracy when getting dimensions from camera images is not the best and varies with the distance to the subject, and the field of view (fov). For example, a wide angle image of the side of a ship taken relatively close to the ship will appear to bulge in the center. This is because the camera is closer to the center of the ship than it is to the ends. An image of the same ship farther away and zoomed in will appear more normal. The distance difference between the center and ends to the camera is less. Think of triangles drawn from the camera, to the center, to the end, and back to the camera for the two images. The difference in the length of the legs is less with the zoom shot. This goes for height as well as width.
High resolution zoomed images are best, they have a smaller fov. Using just a section of an image also lessens the fov and minimizes distortion. Any parts closer to or farther from the camera than the reference part with the known dimension will be either smaller or larger than the results show. The same goes for the center and edges of the photo. If your reference part is in the center, results for parts near the edges will be smaller than actual scale.
You will need a graphics program that allows you to draw a selection on the image and show the pixel width and height of the selection. I use Irfanview for this, a free program with basic graphic editing functions. The selection size will be shown in the caption bar at the top. During installation it may ask if you also want to install Yahoo toolbar so pay attention.
Draw a selection around the reference part you know the dimension of to get the pixel width or height. Enter this in the "Known Pixels" box and the dimension of the part in the "Known Dimension" box. Draw a selection around the part you want to get the dimension of and enter this in the "Enter Pixels" box. The result will be in the same unit of measure (uom) you entered in the known dimension box.
"Error Messages" will show input errors like a letter in a number box, if dimension or scale is missing, or if more than one decimal place is entered. Too small, too large, or too long of inputs will show an error. Too small or too large a result will show an error.
Pay attention when entering a dimension. If you enter a letter for a number, then another number, the error box will clear without your knowing a number is missing. For example if you accidentally enter an "e" for a "4" like this: "275e8", the input box will only show "2758" if you didn't catch the error message.
If results round to zero you will get an error. Try raising the decimal places.
Scale: min 1, max 999,999 or 12 characters including decimal point
Known Pixels: min 1, max 99,999 or 7 characters
Known Dimension: min .0001, max 99,999 or 12 characters
Foot / Meter input: min .0001, max 999,999 or 12 characters
Inch / Centimeter / Millimeter input: min .0001, max 999,999,999 or 12 characters
Pixel input: min 1, max 99,999 or 7 characters
Label: 100 characters
Output: min .00001, max 14 characters
Results: max 100 results