Have you ever wondered what the different drawing file types may mean for you as an Estimator? Surely you have received a range of drawing files from JPEG and PNG; to PDF and CAD. But did you know that all these file types primarily fall into two categories? As crazy as it sounds, most, if not all drawing files can be classified as being either a Raster or Vector file. It is imperative to understand the differences between the two, as the takeoff method is greatly dictated by the file type itself.
Raster- JPEG, JPG, TIFF, BMP
Raster files are images created entirely of small quadrilateral cells which are commonly known as pixels. Millions of these pixels mapped onto fixed coordinates build a complete image. The smaller and closer these pixels are, the higher the quality of the image. And because raster images are formed by a fixed number of pixels, they cannot be resized without compromising their resolution. If you were to enlarge or shrink a raster image, you may encounter a loss of resolution and even disrupt the proportion- thus, altering the original scale.
A drafter may use CAD to draw a plan and publish the file as a JPEG for the ease of sharing. Once exported as a raster, the file will lose its inherent resolution and intelligence. When loaded into a takeoff software, extra care is needed to ensure that the file is properly calibrated and scaled. Measurement of a raster image traces an overlay over the top of the drawing. Users click from pixel to pixel to deduct the desired quantities. And for this reason, measurements generated from raster images are rarely 100% accurate.
Vector – CAD, DWG, DWF, DWFx
Vector images greatly differ to that of raster. They are composed entirely of lines (also known as paths). They use mathematical formulas to draw lines and curves which are combined to create an object. For this reason, vector images retain resolution and scale regardless of size; as the mathematical formulas governing the image is continuous. Vector files also contain more information as they may carry over embedded intelligence from the source CAD files such as layers, blocks, and polylines.
When loaded into an intelligent takeoff software such as eMeasure, vector objects can be taken off by snapping to the exact entity point. This eliminates any deviations from a user having to judge and trace over pixelated lines on a raster image. Other embedded intelligence as noted above will facilitate greater speed and accuracy. Layers will help users filter and isolate relevant details which greatly assist with the speed of measurement. Blocks allow users to count all instances of a block in a single click, while polylines allow the automatic return of the area or perimeter with a single action. When compared with raster files, vector files deliver greater accuracy, speed, and ease of use.
Today, nearly all initial 2D plans are created by drafters as CAD vector files. However, when distributed down the supply chain, they are often converted into raster format for the ease of sharing. Whenever possible, always ask your designers or clients to provide you with vector files such as DWG or even PDF. Never settle for a scanned raster file as a lot of guesswork resulting in inaccuracies may arise. Vector files are intelligent and will catalyse faster and more accurate results.
If you want to learn more about the different files types and measurement methods available on eMeasure, you can download our eMeasure Drawing File Optimisation document here. For any other questions, please feel free to contact us here.