By Dan Bouchard

One of the problems when planning a renovation of an older building is that the original plans for the building were most likely drawn before the “digital age”. So as an Architect, Engineer or Contractor you have been hired to facilitate a renovation and you have been handed an old set of mylars, vellums or worse, blueprints to work from. What do you do? How do you get these old drawings into a digital format for use in your CAD program?

There are three distinct options for turning paper drawings into digital. The first option is to simply redraw them in your CAD program. And although this is probably the most inefficient way of converting to digital, it is the most common. Not only is this method time consuming, but it also lends itself to errors. The second option would be to have your drawings scanned on a wide format scanner as a .tif file. (.tif by the way, is the default file format for large format scanner that most reprographers use.) You should be able to have this done for a minimal price per drawing. Most CAD programs will import .tif files as a background image. But remember, since a .tif file is a raster image and not a vector image, you will not be able to make changes to it in CAD. You can draw on top of it, but that’s all. In some cases this may be enough, but if total flexibility with the drawings is what you need, you should choose option three and have them converted to a vector file.

What is the difference between a raster and a vector file? A raster file is, simply put, a picture. It cannot be manipulated. Sure, you can bring it into a photo program and do some rudimentary editing, but you will need a steady hand and keen eye, and chances are, in the end your scale will be off. On the other hand, in a vector file all parts can be manipulated. Each line, curve, font, symbol or other part of the drawing is its own object. Grab it, move it, make it bigger, smaller, longer, shorter. Turn it, flip it or color it. Your CAD files are vector files. Digital pictures of your kids are raster files.

Converting drawings to vector files is not cheap. The going rate is between $100 and $200 per drawing depending on the complexity. But if you stop and consider the cost to have them re-drawn from scratch, you’ll see that it is a lot more economical to have them converted. You can also have these converted drawings saved in the format of your choice. Be it AutoCad, Microstation, or whatever. Most well known CAD programs are supported.

Finally, there are a number of software packages out there that claim to do raster to vector conversion. I have yet to see one that works consistently. Your best bet when having this done is to contact a professional.

Filed under: Plotting