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Dr.Dejan GAVRAN,dipl.ing.



GAVRAN – Civil Modeller





Latest versions of GCM

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GCM – Development History

by Dejan GAVRAN



Even as a student of civil engineering, in early 1980-es, I was heavily involved in computer programing. I think, at least quarter of the students from my generation were pretty good programmers. It was a pioneering time and our ambitions were far from the commercial ones. We were just enthusiastic about making our students projects easier to do and, of course, about making our examinations easier to pass.

In 1985-86, while preparing for final exam, I developed software for drafting perspective views of the road from the driver’s eye position. Unlike simple axonometry, characteristic for early releases of AutoCAD, the software was drafting real perspective views on Commodore C64. For just one colored wire frame picture there was 2 to 3 minutes of calculation. In essence, the software was resolving many aspects of road design. The input was pretty row: terrain surveys, basic elements of horizontal and vertical alignment, elements of the typical cross section, criteria for applying retaining walls etc. Before generating the picture itself, the software was supposed to recalculate the entire roadway morfology.

In the years to come (1987-1990) I moved to Apple MacIntosh. I continued with upgrading software for the perspective view of the roadway, but also developed software for traffic network simulations (gravity model, Moore-Dial algorithm, shortest path through the maze, traffic distribution etc.), for finite element analyses of the pavement structures, for aircraft noise simulation and mapping. By the end of the 80-es, I also did some software for PC, mainly for the simulation of the aircraft movement. But, even when working on Mac, which was exceptionally friendly for programming, most of the programming code was not about the engineering calculations themselves, but about mouse control, zooming in and out, plotting control etc.

In 1990. I definitely moved to AutoCAD on PC platform and it was great relief for me. All general purpose options (mouse control, zooming, plotting, general editing) were already present and the core of the engineering problem could have been solved by using AutoLISP, very “fluent” dialect of LISP (stands for LISt Processing), which happened to be one of the oldest programming languages. The first serious undertaking in AutoCAD was AeroCAD, developed in 1990-91 while working on master degree thesis, on AutoCAD Rel.10 and AutoCAD Rel.11 platforms. It was entire package covering all aspects of the airport’s airside design in plan projection: aircraft movement simulation, design of runways and taxiways, apron and holding-bay design, simulation of parking maneuvers, positioning of passenger bridges, marking and lighting, positioning of navigational aids etc. The upper part of vintage AutoCAD Rel.10 tablet (to be put on digitizer for easier and more accurate mouse movement), containing AeroCAD commands, is given on Fig.2-01.

Fig.2-01. AeroCAD commands          

Besides AutoLISP, AutoCAD Rel.11 (in 1990) enabled compiled C code to run within AutoCAD. Thus, it finally became possible to seamlessly incorporate the most time consuming calculations in AutoCAD based packages - calculations like TIN (Triangulated Irregular Network) generation, prismoidal volume calculations, extraction of profiles and cross sections, generation of cut and fill slopes etc. While working on doctoral thesis (1993.), my ambitions moved from 2D to 3D. In 1993. The first version of GCM was created, and the name was AeroCAD 3D (Fig.2.-02). The intention was to create the software for airport design in 3D, which is more complex than developing software for road design only. While the road is typical linear facility, the airside constitutes a system of interlinked linear and planar facilities. Even the general cross section of the airside is more complex than the cross section of the road, because it contains cross section of the runway, cross sections of parallel taxiways and sometime aprons, and all these facilities are interlinked with the complex and expensive elements of grading.  General idea was to develop fully three-dimensional software that would generate triangulated model of the airside. And all the cross-sections and profiles would be simply cut out from the model’s triangles. Also, the grading plans would be generated by cutting the model’s triangles with the series of imaginary horizontal planes placed at the constant intervals. Volumes would be calculated between the triangulated networks as well. Finally, the finest shapes of grading were supported, even the modeling of intersecting cut and fill slopes, which was out reach for many software solutions of the era. Special set of commands for fine modeling of runway-taxiway and road intersections was developed. The first version of software was completed in autumn 1993, but for next four years it was not commercially available. It was thoroughly tested and used on some in-house projects.


Fig.2-02. AeroCAD 3D commands

After passing final doctoral examination by the end of 1996, I was asked by the local engineering community to make the software commercially available. Thus, in May 1997 (AutoCAD Rel.14 era), after producing user manual and making some final touches, the software was sold to first design bureaus in Israel and former Yugoslavia. The name of the software was changed – it became GAVRAN – Civil Modeller, or GCM. Also, some options that proved to be too specific for the airports were removed (such as the options for checking the obstacle limitation surfaces, windrose analyses etc.) and some new were added.

In order not to compromise GCM, I was refusing to sell the product in larger quantities. Though there was a pretty good written manual, I insisted on giving 4-5 day free course for each new customer. As I was always a single developer, that fact was limiting sells to one or two new customers per month.  But, GCM was quite a success. For example, it was possible only with GCM to model the entire corridor of the motorway and then to extract the perfect cross sections, containing not only the motorway itself, but also the service roads,  regulated riverbeds, tunnels and bridges, even the nearby houses … everything that had been constructed by using GCM’s triangulated models. By the end of the 90-es the software was tested on very demanding tunneling projects in Austria and later in Switzerland.

By year 1999, requests for GCM went higher. In order to satisfy new customers, but still maintaining the high level of training, I decided to create the first video tutorial. Thus, GCM2000 (AutoCAD 2000 era) came with both written and video documentation (with more than 6 hours of video files). GCM2000 introduced dynamic triangulated models, even the dynamic crossroads, which was also ahead of the time.

GCM2004 upgraded dynamic 2D and 3D behavior in general and also introduced dynamic behavior of simulated vehicle trajectories.

From technological and scientific point of view, GCM2006 was one step back. Though full 3D had always been a main characteristic of GCM, local engineering community was expecting simplification in the design of purely linear facilities. Therefore, CSC macro language (Cross Section Constructor) was developed. The language conceptually resembles graphical languages for guiding the antique pen-plotters from 1970-90. era, but its syntax reflects the geometrical reasoning specific to the cross section construction.

GCM2009 (or GCMx64) provides kind of a graphical substitute for CSC coding. CSC code is now automatically generated from the graphically defined road details. Also, GCM2009 introduces calculation of available sight distances from the 3D model and the simulation of vehicle maneuvers is performed by pushing and pulling the vehicle like toy.

GC2013 (or GCM++) further automates CSC concept, provides support for speed analyses for both passenger cars and trucks, upgrades optical analyses of the road, greatly improves 3D model dynamics by combining the traditional 3D modeling techniques and CSC concept and introduces 3D printing.






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