Landscape Architect Articles

technology08-23-05 | News

Raster to Vector at the Click of a Button

By Scott Weinberg,
Technology Editor, University of Georgia, Athens

As a teacher and practicing Landscape Architect I have always found it time consuming to sit at the computer screen and trace over a raster image, usually a photograph or scanned image, to create a basemap that can be read in AutoCAD. A typical contour map that began as a 36” x 24” original sheet, with as many as 50-60 contours could take as long as 4-5 hours to copy.

I was introduced to the TracTrix program in its original format back in the late 1990?EUR??,,????'???s. With the latest release of the program, it has become both leaner and more efficient than its predecessor. The program itself can handle three distinct operations:

Raster to Vector Conversion, converting scans to DWG, DXF, HPGL and IGES formats.
Vector to Raster Conversion, for converting DWG, DXF and HPGL to PDF and raster file types.
Viewing and Markup, for measuring, printing and comparing drawings.

Most likely the main reason to get involved in the program is to use the Raster to Vector conversion feature. The files that can be read in raster format to be converted to vector seem endless.

Using this program and a scanner, I was able to create a JPG and import the image into the program. With a click of the mouse and 30 seconds later the program had converted the image to a VECTOR, or CAD image that could now be saved as a DWG file. Just like that, it was that simple. Now I have a fully functional CAD drawing of the lot, complete with house! The only thing left for me to do was to scale the drawing in AutoCAD.

While putting the program through a few test conversions I was able to see just how quickly and easily the program functions. I also became aware of a few pitfalls, not necessarily the program?EUR??,,????'???s fault. The first test sheet I used was that of a partial floor plan.

Fig. 1: This PDF file was the file used to convert the raster image into a DWG file. Specifically look at the area of the stairs in the upper right hand corner.

Fig. 2: This conversion took place using a 300 dpi scanning resolution and resulted in a poor CAD drawing.

Fig. 3: Increasing the scanning dpi from 300 to 600 resulted in a much better and acceptable DWG file.

(FIG 1) I scanned the image in at 300dpi and saved it as a JPG. Using the program I converted it to a DWG file and the results can be seen in FIG 2. Not really what I was hoping for. Looking around the programs ?EUR??,,????'??help?EUR??,,????'?? area I could understand what might have been the problem. A second scan was done at 600dpi and the acceptable results can be viewed in FIG 3. A simple tweaking up of the resolution was all it took.

Fig. 4: This is a basic contour map that could be anywhere. It was used as the base scan for creating a DWG file.

Fig. 5: The contour map transitioned easily and flawlessly into the DWG file that can be read by AutoCAD and is ready to be edited.

A second test scan I ran was using a contour map that was scanned in at 600dpi. The basemap was similar to the basemap in FIG 4. Within a few seconds the map turned from black and white to a blue and white image showing that the conversion had already taken place. The DWG file itself was a flawless CAD file that was ready to be edited (FIG 5). Be aware that there are some things the program will not handle that I am sure you wish it would. For example, when converting a contour drawing into a DWG file, the CAD drawing lines will not contain and information regarding the ?EUR??,,????'??z?EUR??,,????'?? coordinate. Meaning that even though the contour is labeled as 654?EUR??,,????'???, the ?EUR??,,????'??z?EUR??,,????'?? information that is contained in the drawing for that contour will be ?EUR??,,????'??0?EUR??,,????'??. You will have to do a change command and reset the ?EUR??,,????'??z?EUR??,,????'?? value for each contour.

While working with a scanned image, the program will allow you to actually draw on top of the image using vector type lines, circles and rectangles. Therefore you are already beginning to create a CAD readable file even before the actual conversion takes place.

Some features in the program include the ability to figure out the scale of an existing drawing by selecting two points on the screen. After you select the points a dialog box pops up and will ask you what the known distance is. It will automatically tell you the scale of the drawing. Another helpful feature is a raster eraser. This tool will allow you to erase any unwanted features before you convert the scan into a CAD file. The program will also allow you to add to your raster image by letting you add new details as lines in either the raster or vector format.

After an easy installation, no hang-ups or problems, I was able to import a scanned image and convert it to a vector drawing in 10 minutes. The program can save hundreds of hours of time over the course of a year. The system requires only that you use Windows 2003, XP, 2000, NT4.x, 98 or 95. You can visit the website for more information at www.trixsystems.com. There is a free trial download available. Take it for a test drive!