AllyCAD Showcase

'Begin with the Survey'


City of Cape Town

Surveyors are the first people into the green fields to prepare the landscape for future development. People tend to take the hidden parts of infrastructure for granted. Turn on the tap and water just comes out.

"Sometimes in the planning not enough emphasis is placed on these non-visible services. You can't have a clinic or a library without a road to service it. Medicines, books and personnel can't get there, the people can walk there, but that's no good if there isn't anybody to help them. And before you build it, you have to survey it," says Peter Whitwam, Senior Survey Technician of the City of Cape Town, based in Durbanville.

Peter is a 26-year veteran surveyor of many local government councils in the Western Cape. "As the various councils have come and gone due to political changes, I have actually changed employers many times but have never had to resign," he says.

Recalling his early days as a surveyor, he reflected on the changes in technology that have shaped the huge growth of the urban landscape. "Sometimes I would spend one whole day trudging through the bush just to fix one point. We had no cellphones, no radios - no communications at all. It was really hell when we had a puncture! Today, however, you have the drawback of having to carry so much battery power needed to run everything."

"When I started my career, there was still wildlife in Mitchells Plain - bokkies and similar wildlife, not the gangster wildlife that the area has unfortunately become known for now. Khayelitsha was not there then - it was a military area; there were even stud farms nearby."

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Technology has made working a lot easier. "Probably the most significant improvement has been in accuracy. In the late 70's through to the late 80's I worked in the raw bush where Atlantis is now. Using a prism bank and an electronic distance meter you could work accurately on distances up to 2km. Over longer distances you had to use resections and triangulation that provided acceptable accuracy 10-20cm either way. Today you use a GPS that gives you an accuracy of 2cm either way over vast distances - and heights as well."

"Maybe people are getting too fussy these days, because they are getting these accuracies, but when you are pushing around a lot of earth, just how accurate do you really have to be? There is a danger though; in the past you would plot your data on a plan that had a particular scale. People would then measure and take co-ordinates off that scale. Now with digital data, some people take information that might have been captured to the nearest metre, and then try and get millimetre accuracy off it. For example, they take an aerial photograph that is at a scale of 1:10 000, blow it up to 1:500 - because they can - and then try and get 1:500 accuracy off it. That is inaccurate, you simply can't do that," says Peter. "Very often the meta-data - the accuracy that the data was captured with - is ignored."

Computers have always been around during Peter's career. "From the start, we had Wang mainframes that had software that was developed in-house. We used these right up to 1997 when the Western Cape Regional office was disbanded. CIVIL DESIGNER and ALLYCAD were chosen by Tygerberg Municipality and I have been using it ever since."

"The huge benefit of these programs is the seamless integration of the CAD, survey and design software into one module. The city has a lot of data that was captured on GIS that you bring straight into your CAD drawing, snap off the co-ordinates, and do your drawings. You don't have to sit and calculate anything, you can just draw. You then snap off the co-ordinates and set it out in the field."
  "Another big benefit is bringing in the photography. We have aerial photography of the whole city, and being able to bring in the aerial survey backdrop gives you the ability to do an on-screen field check. The backdrop is not good enough to draw off it, but being able to see a driveway or a gravel track is an absolute bonus," says a delighted Peter.

The biggest job Peter has done at Durbanville was a joint project with Jeffares & Green who did a 'one-way road system'. "Because I could do the survey in-house - at about a third of the commercial rate - we were able to spend that saving more beneficially with Jeffares & Green. That survey involved 13 000 tache shots, all done by me and Herbert Mgudlwa, my long-standing survey assistant."

"We scanned analogue map images of Durbanville that were done in '86, and brought those in as backdrops. Because Jeffares & Green use the same software, there were no compatibility problems. Although the concept was not implemented as such, the council still gets enormous benefit from the study as it is still used to guide all road accesses etc, for all developments in Durbanville. The benefits will last for about ten years."

Training enjoys a high priority in the Council. "Alwyn Laubsher, the former head of Civil Engineering at Tygerberg was very keen on student development. From that legacy, the city gets about twenty civil engineering students doing their in-service training each year, and I basically teach some of them how to use ALLYCAD and CIVIL DESIGNER in a 'real-world' environment. I enjoy the teaching and get a lot of satisfaction from training. The more you put into the students, the more you get out of them. I like to keep them busy and vary their projects."

"Here in Durbanville the students produce most of the CAD and design work under supervision. They are given what we call Ward Allocation Projects. These are always tight on budget - there are always more projects than there is money. For example,

a sports field would not have money to spend on an outside firm, so we do those projects internally. It really is a win-win; the students get excellent experience and training, and the citizens get a much needed facility that was not possible due to budget constraints."

Peter is currently busy with a collaborative project. "Slent Road is a 10km gravel road that needs to be bitumen surfaced due to increased traffic volumes. The project is mainly being done in-house. I am currently working with an engineer who guides me on the design while I work on the computer - a very efficient and cost effective way to work."

One of the finest benefits of using the software is being able to change the set-up of the drawing from Cartesian to Survey mode. "Just one click changes the co-ordinates from negative to positive. When we use the GIS data, it is so easy to switch the data from one mode to the next. I find that ALLYCAD is really very easy to use."


 
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