Gunnar Liden

Mittelwiesstrasse 39

CH-8708 Männedorf


Tel. +41 43 810 54 33










Before there were any CAD systems on the market, aircraft companies used own-developed Surface Definition Systems to mathematically define aircraft shapes. Some of these systems later became commercial CAD systems like for instance Catia from Dassault. My career as a programmer of CAD functions started with the Saab FORMELA system and the British Aerospace system NMG. My actual job was to define surfaces, but the functionality in FORMELA and NMG was not sufficient. Special support and analysis functions were always needed to be able to handle all the requirements from the aerodynamic, design, stress, manufacturing and material people.


Very early in my surface definition work I started to use non-linear optimization methods. Such methods require mathematical criteria for the quality (fairness) of curves and surfaces. One of the first things I developed was a spline smoothing method based on curvature. This smoothing function was implemented in the Gerber CAD system and Saab Automobile used it for many years. For surfaces I used lines of curvature and other curvature criteria, surface normal variations and special FANGA curves. The FANGA method was published in the Computer Aided Design Magazine, and was also presented at a Catia users meeting and at a mathematics conference in Edinburgh.


At Saab I started in the Geometry Group, became later the team leader for four geometry programmers and ended as a Geometry Specialist, which is the top position of the Saab technical career. I have also been project leader in a CIM composite material project and I was Saab’s project leader in the EU MEDIATE project.


All my Saab years I had a close cooperation with the universities in Linköping, Stockholm, Örebro and Birmingham. I have contributed to research projects, I have made presentations, and I was almost every year supervisor for one or two students doing their master thesis at Saab. For two months I was also in Birmingham participating in a Surface Mathematics project.


I have implemented geometry functions in the systems: NMG, APT140 (a NC system), Catia and in Varkon ( I also implemented interfaces between many of Saab’s and Saab partner’s CAD and NC programs. In Catia I programmed sheet-metal and composite material functions. Many geometry applications were implemented in Varkon. One of the more exciting ones was a radar signature calculation. This application was run (is perhaps still running) in a Cray super computer.


Varkon is “my” CAD system since I practically implemented all the curve and surface functions in this system. Varkon is a Generic Model (History tree) type of system where Product Model applications can be implemented. I have at conferences and in a paper presented such applications. 


At Prosolvia I developed simulation functions and an interface from Robcad to ACIS.


At Leica Geosystems I implemented the Varkon Generic Model in AutoCad as a prototype, I developed measurement functions in the Horizon system and I transferred CAD knowledge to developers, supporters and sales people. I was also Leica’s project leader in the EU ADFAST project ( 


At Phonak: Development of functions in the RSM system. In RSM are shells for hearing instruments defined.  





2005 –                       Phonak, Switzerland


1999 – 2005             Leica Geosystems, Switzerland


Position                      Senior Software Engineer

Development of functions in the Horizon measurement system including the selection of a base CAD system (Mechanical Desktop) and implementation of a Generic Model (History Tree) as a prototype.


Other tasks                Seminars to transfer general CAD knowledge to the software development team.

CAD import (interface) seminars for all Leica support and sales people.

Leica’s project leader in the EU project ADFAST. Leica’s contribution was to integrate a tracker with a robot for the building of a flexible tool, i.e. a tool that can be used for many assemblies.


1997 – 1999             Prosolvia, Sweden


Position                      Senior Software Engineer

Interface between Robcad and Prosolvia’s Digital Plant system that was based on ACIS.

Function to define mounting paths for parts in an assembly (avoid collisions).

Implementation of functions in a Discrete Event Simulation program..



1988 – 1997             Saab Aircraft, Sweden


Position                      Geometry Specialist

Development of many geometry applications in Varkon like for instance: Radar reflection, Optical analysis, Definition of satellite antennas, Weight prediction and Measurement analysis.

Evaluation of CAD systems.

Evaluation of Rapid Prototype systems.

European Catia User Association (ECUA) Saab representative in the Surface committee.

Leader of a CIM Composite Material Project.

Saab’s project leader in the EU project MEDIATE, where methods and software were developed in order to improve manufacturing quality. Saab’s (my) contribution was a product model type of application for wing analysis based on measured point data.


1982 – 1998             Saab Aircraft, Sweden


Position                      Software Engineer and Team Leader

Curve and surface functions in NMG. NC functions in APT140 and Catia. 

Sheet metal and composite material functions in Catia.


1977 – 1981             Saab Aircraft, Sweden


Position                      Geometrician (lofting group)

Definition of surfaces for a trainer aircraft, Saab 340 and Gripen.

Programming of curve and surface functions.



1973 – 1976             Saab Aircraft, Sweden


Position                      Buyer

Purchase of equipment for the Viggen fighter




·        Roland Zumbrunn, Leica Geosystems, Tel. +41 62 737 68 18

·        Additional names available on request from Saab Aircraft, Saab Automobile and Universities




·        Gunnar Liden and Alan Ball, Intersection techniques for assessing surface quality, Design and Applications of Curves and Surfaces, Mathematics of surfaces V, Oxford University Press 1994

·        Gunnar Liden and Stefan Westberg, Fairing of Surfaces with optimization techniques using FANGA curves as the quality criterion, Computer Aided Design Magazine, volume 25 number 7 July 1993.

·        Johan Kjellander, Gunnar Liden and Bengt Nilsson, Product Models for Design and Manufacture, Örebro University 1992 (in Swedish).







2004               Metrology-integrated Industrial Robots, International Symposium on Robotics, Paris

1996               Optimization algorithms and calculations in 3D available to Designers, ECUA (Catia user meeting), Gothenburg

1996               Overview of parametric methods in CAD systems, Parametric Design conference, Saab Aircraft (chairman and speaker)

1995               Minimize routine work at design, Designers Conference, Gothenburg

1995               Generic product models for design, Product models conference, Linköping

1994               How to integrate a new CAD system in a company, Stockholm

1992               Fanga surface quality criterion, Institute of Mathematics and its Applications conference in Edinburgh

1983               Surface quality criteria, AECMA meeting, Linköping





·        Languages: English, German and Swedish (mother tongue)

·        Programming: Fortran, C, C++, XML, script languages, UML, Unix, Windows, TCP/IP, WinSocks

·        Applications: Mechanical Desktop, Surfacer, Catia, NMG, APT140, Gerber





1969  - 1973                    Mechanical engineering and Economy, Linköping University, Sweden

1968  - 1969                    Mathematics, University of Växjö, Sweden






First name



Mittelwiesstrasse 39

CH-8708 Männedorf




+41 43 810 54 33



Date of Birth

September 13th, 1947






Two daughters (Lena 1977 and Karin 1979). Divorced.



Kayak paddling. Organizer of jazz concerts and Webmaster for the jazz club.