The use of the spline function in computer-aided type design

The traditional type designer works with pen, in and paper. The characters that he designs go through many changes before the whole font is finalized and set in the printing medium. Further alterations to the font may occur after he prints and evaluates a sample piece of text. Computer-aided type design presents the type designer with a new design tool. Computers have been used in the printing industry for typesetting; the automation of type design is a logical next step. Freeing the designer from the repetitive tasks of the design cycle is one obvious advantage cf using computers. But computer-aided type design makes its real contribution when a designer can use it with the same facility that he uses traditional design tools like pen, ink and paper. This research investigates the use of the spline curve in type design. Contemporary type designers are expected to perform a variety of tasks. On the one hand, they may design characters that will last because of their artistic merit and singular characteristics. On the other hand, they may design characters that can be recognized by machines. A computer-aided type design tool should be flexible enough to meet these demands and con venient to use. The focus of the research will be on the input requirements for drawing the spline curves that form the characters. First, the mathematics of the spline functions and their use in two dimensional graphics is discussed. Next, a brief survey of the use of the spline curve in computer-aided type design is given. In order to investigate further the problems of designing characters, a pilot system was written to design basic character shapes, using raster based graphics. The system was designed with the objective of having input specifications which would be familiar to a type designer. This system is described in the last section

Application of desktop manufacturing system (SLA) for the manufacturing of a centrifugal pump impeller using CAD (I-DEAS)

Desktop Manufacturing (DTM) systems which combine personal computer, laser and other technologies are being used to sculpt objects from computer generated models created on computer aided design (CAD) workstations. As a member of DTM systems, StereoLithography Apparatus (SLA) transforms 3-dimensional designs into a 3-D output. This can substantially reduce the time required to produce a prototype through the process of photopolymerization. The process involves the transfer of a liquid plastic monomer into a solid polymer by exposing it to ultraviolet light. Although the process looks productive, inefficiencies can occur, if incorrect parameters are selected before its application for a particular prototype fabrication. In understanding the correct requirements of the prototype being built, efficiency can be maximized by the use of desktop manufacturing systems

The statistical properties and coding of handwriting and hand-drawn graphics in tutorial classes

This research investigates compression techniques as applied to input from a digitizing tablet. The representations we consider are either drawn from the literature or developed within this thesis; they involve selecting relevant points along the trajectory of the writing pen, and using an interpolating function for reconstruction. The two dimensional parametric polynomial interpolator (e.g linear, quadratic, cubic ) is used for regenerating the trajectory of the pen. Several techniques for selecting relevant points , i.e control points are discussed. We determine our best representation by weighting the criteria, analyzing the experimental results, examining the theoretical considerations and, making where necessary, justifiable tradeoffs. The techniques tested are objectively evaluated in terms of accuracy, efficiency and compactness. The information characteristics (i.e signal entropy) of the handwriting and drawing signals, are estimated from the original and approximated data. Results are discussed and conclusions drawn. The research has been carried out on static data

Strategies for teaching engineering mathematics

This thesis is an account of experiments into the teaching of mathematics to engineering undergraduates which have been conducted over twenty years against a background of changing intake ability, varying output requirements and increasing restrictions on the formal contact time available. The aim has been to improve the efficiency of the teaching-learning process. The main areas of experimentation have been the integration in the syllabus of numerical and analytical methods, the incorporation of case studies into the curriculum and the use of micro-based software to enhance the teaching process. Special attention is paid to courses in Mathematical Engineering and their position in the spectrum of engineering disciplines. A core curriculum in mathematics for undergraduate engineers is proposed and details are provided of its implementation. The roles of case studies and micro-based software are highlighted. The provision of a mathematics learning resource centre is considered a necessary feature of the implementation of the proposed course. Finally, suggestions for further research are made

NASA Tech Briefs, June 1989

Topics include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

A kinematic numerical camera model for the SPOT-1 sensor

A novel method for modelling linear push-broom sensors has been developed. A numerical model which incorporates the satellite attitude and position data is used to compute the absolute orientation. This method makes a break with traditional photogrammetric practice, in that instead of using an approach based on collinearity equations, the absolute orientation is computed iteratively using a numerical multi-variable minimisation scheme. All current implementations of the model use the Powell direction-set method, but in principle, any multivariable minimisation scheme could be substituted. The numerical method has significant advantages over the collinearity approach. The number of ground control points needed to form an accurate model is reduced and the numerical approach offers a superior basis for the development of general purpose multi sensor modelling software. In order to test these assertions, a numerical model of the SPOT-1 sensor was coded and tested against a pre-existing collinearity based model. Exhaustive tests showed the numerical model, using 3 or fewer ground control points, consistendy equaled or bettered the performance of the earlier model, using between 6 and 15 ground control points, on the same test data. A general purpose sensor modelling system was developed using the code developed for the initial SPOT-1 model. Currently this system supports many rigid linear sensors systems including SPOT-1, SPOT-2, FTIR, MISR, MEOSS and ASAS. Further extensions to the system to enable it to model non-rigid linear sensors such as AVHRR and ATM are planned. Work to enable the system to perform relative orientations for a variety of sensor types is also ongoing

The efficient use of data from different sources for production and application of digital elevation models

The emphasis of the investigation reported in this thesis is on the use of digital elevation data of two resolutions originating from two different sources. The high resolution DEM was captured from aerial photographs (first source) at a scale of 1:30,000 and the low resolution DEM was captured from SPOT images (second source). It is well known that the resolution of DEM data depends a great deal on the scale of the images used. The technique for capturing DEMs is static measurement of the spot heights in a regular grid. The grid spacing of the high resolution DEM was 30 m, and of the low resolution DEM was 100 m. The aims of this thesis are as follows: 1. To assess the feasibility of using SPOT stereodata as a source of height information and merged with data from aerial photography. This is carried out by comparison of the elevation data derived from SPOT with the digital elevation data derived from aerial photography. From the comparison of these two sources of height information, some results are derived which show the possible heighting accuracy levels which can realistically be achieved. A systematic error in the estimated average of the elevation differences was found and many tests have been carried out to find the reasons for the presence of this systematic error. 2. To develop methods to manipulate the captured data. 2.1. Gross error (blunder) detection. Blunders made during the data capturing procedure affect the accuracy of the final product. Therefore it is necessary to trap and to remove them. A pointwise local self-checking blunder detection algorithm was developed in order to check the grid elevation data, particularly those which are derived from the second source. 2.2. Data coordinates transformation. The data must be transformed into a common projection in order to be directly comparable. The projection and coordinate systems employed are studied in this project, and the errors caused by the transformations are estimated. 2.3. Data merging. Data of different reliability have to be merged into a single set of data. In this project data from two different sources are merged in order to create a final product of known and uniform accuracy. The effect of the lower resolution source on the high resolution source was studied, in dense and in sparse form. 2.4. Data structure. To structure the data by changing the format in order to be in an acceptable form for DEM creation and display, through the commercially available Laser-Scan package DTMCREATE. 3. DEM production and contouring. To produce DEMs from the initial data and that derived from the two merged sources, and to find the accuracy of the interpolation procedure by comparing the derived interpolated data with the high resolution DEM which has been derived from aerial photography. Finally to interpolate contours directly from the "raw" SPOT data and to compare them with those derived from the aerial photography in order to find out the feasibility and capability of using SPOT data in contouring for topographic maps

NASA Tech Briefs, July 1992

Topics include: New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Geometrical modelling and graphics display of stratigraphic orebodies.

In this research project the author introduces the use of geometrical modelling techniques alongside geostatistical methods to model a stratigraphic orebody and to present a graphics display system developed as a fIrst step towards a general integrated system for computer aided design and planning in mining. Geometrical modelling techniques and geostatistical methods are combined to carry out the process of modelling a stratigraphic orebody. From a mining point of view, there are two main features of interest in a stratigraphic ore-body: a-The modelling of the geometry of the orebody. b- The modelling (estimation) of the physical properties (grades, etc ... ) of the orebody. The first feature is the subject of this research project. Modelling methods and techniques developed elsewhere and for different applications, such as Computer Aided Design, have been applied successfully to model the geometry of stratigraphic orebodies. The modelling process consists of the applications of surface modelling techniques to represent the hangingwall and the footwall of the stratigraphic orebody and thereby to produce the space where the physical properties are geostatistically to be estimated. The graphics display system is presented to highlight the use of computer graphics techniques to communicate graphically all sorts of information concerning the modelling of stratigraphic orebodies and also to display the end product of the modelling process, such as cross-sections, plane-sections, wireframe and solid models of the orebody. The graphics system itself is part of a computer based system for mine design and planning similar to computer aided design systems used mainly in the manufacturing industry. The presentation of the research project in this thesis started by the review of the literature of some existing ore reserves estimation methods in the mineral industry, particularly geostatistical methods. Then an overview and the scope of this research project have been given. The second chapter describes the type of data which could be encountered while building a geometrical model of a stratigraphic orebody and a description of data from a nickel vein deposit used as a case study for this research project. The accumulations have been estimated geostatistically subject to geometrical control. The geometrical control concept and surface modelling techniques are presented in chapter three together with the numerical application of modelling a nickel vein deposit using two different surface modelling techniques. Chapter four describes the graphics display system developed to display several geometric features of stratigraphic orebodies in two and three dimensions. The summary of this research project and some concluding remarks are given in chapter fiv