Data Prep: Tips, Tricks & Techniques: Just build it off of the CADD

Written by Chad Cooper

Created on Tuesday, 01 December 2009 17:15

Its something that eventually everyone who builds data will hear from their client: "Just build it off of the CADD". In an ideal world, you would always have a set of paper plans along with your CADD files (or Microstation, Terramodel and so on) before you worked on any data projects. However, whether its because the paper plans are not available from the engineer or there is not enough time to wait for them to show up in the mail, its becoming more common to have no choice but to do your work based only on the CADD files form the engineer. That reality for us data builders begs the question: Should you build data with only a CADD file and no other source of information? It is that question that I hope to answer and discuss in this months article.

As I have pointed out in my articles numerous times, our standard operating procedure is we need paper and CADD. Whether the paper is scans or a hard copy doesn't matter, we just need it. In our increasingly electronic world of engineering design, it is becoming more and more common for both of these sources of information to be provided directly from the engineer through an FTP site or email. Regardless of whether it comes directly from the engineer, or through our client, we always work to get the paper for a number of reasons. It is not uncommon for us to delay starting a project while we wait for the paper plans to arrive. If our client has a need to start immediately, I always push to provide a rough, mass grading file while we wait for the paper rather than go ahead and completely build it to finish without the paper.

But lets be realistic. Paper plans are not always going to available for every project. There are any number of reasons why this may be the case, but the reason doesn't matter. If you don't have the paper and can't get the paper, then you don't have the paper. This is when the instructions to "just" build it off of the CADD come through from your client. When this is the case, there are numerous things that you need to be aware of and pay attention to - too many to fit into an article of this length. Following are what I consider to be the two biggest considerations when working only with a CADD file.

First, you must take a close look at those CADD files and determine if it even possible to build the project off of "just" the CADD files. Did all the linework come through? Does it appear that all the proposed features came through intact? Do the contours look complete? Are there spot elevations? Do the Northings and Eastings look okay? These questions can be at times hard to answer as you don't have anything to compare the CADD against. Regardless, you can usually tell within a few moments whether the CADD files are complete or missing some critical components. This works great for most projects, but there are special consideration for any roadway type project. As opposed to a simple site project where you only really need site linework, contours and spots, your typical roadway project will require plan, profile, typical section, cross sections, super elevation transitions, intersection details, driveway details and so on. We build countless simple site projects throughout the year without paper, but I have not, and will not ever build a heavy highway project without paper. There's just too much detail and information that can not all be contained in "just" the CADD files. Therefore, outside of most roadway projects, there are usually no major setbacks with missing data in the CADD files.

However, even if all information is present in the CADD files, is everything correct? The biggest sole reason that we always strive to have paper plans and CADD information is to compare the two. If anyone of us data builders had a nickel for every time the paper and CADD did not match there would be no need to work. All too often changes have been made and one outdates the other. Perhaps the paper was a bid set and the CADD is from the final design. Perhaps an addendum was released in the paper but the CADD was never updated to reflect the change. Regardless of why they are different, it is very common for us to see this problem. Having only the CADD, there's no way for you to know. The engineer could have inadvertently emailed you last years file and you go on your merry way building data out of it. Then you get a lovely phone call from the field that your model is in the wrong place, with the wrong features and at the wrong elevation all because you unknowingly used an old CADD file. For this reason, when I have no other choice but to build data without paper, I make it very clear to our client that my work is based only the CADD and that any errors or omissions in the CADD file will be in my work. This is stated in the project file, in the email to the client and over the phone. I make very clear to our client what our model is, and what it isn't.

So can you build data without paper plans and "just" off of the CADD? Simple site, yes, as long as the files provided were complete. Heavy highway? Never. But even when it is possible, it is less than an ideal situation for both your and your client. Universally ask for paper, whether a hard copy or scans, wait for paper and work with paper plans for all your data projects. This will ensure that your work is correct, complete and accurate. If its not available, do everything in your power to still make sure your work is correct, complete and accurate. Work as closely as possible with the engineer to ensure that the CADD information provided is up to date and accurate. By doing so you not only protect yourself and your work, but make certain that the data which leaves your office will provide your client with the best information available enabling them to make the most out of their GPS equipment. After all, that's what we are here for.