A Visualization System for Tidal Basins Kenrick Mock

A Visualization System for Tidal Basins Kenrick Mock CS 470

System Overview • Goal – Develop a system to graphically visualize properties of tidal basins – Client is Coastal Engineering • Why – Visualization will aid in the analysis of coastal erosion, effects of pollution, navigational access, and other aspects of waterways – To visualize the system today, Coastal Engineering uses a manual process of loading data into Excel

Data Files • Area of interest divided into 2 D grid of cells. Five files containing source data. – Depth • Depth to basin floor, -99 to represent land – Elevation • Height of the water, indicates tide – U velocity • X velocity of water in a particular cell – V velocity • Y velocity of water in a particular cell – Concentration • Percentage of contaminant or other material in a particular cell

Data Source • Physical Model – Miniature version of the real thing • Computer Model – Fortran program – Most data in this project generated from a computer model

Data File Format • All files are in text • Depth file example -99. 00 3. 96 • Mapping 3. 96 -99. 0

Time-Based Files • Typically 2 -5 Mb in size • Value of each cell specified for a time period VERTICALLY AVERAGED BOD DAYS= 2. 0833334 E-02 HOURS= 0. 5000000 -2. 00 1. 00 -2. 00 VERTICALLY AVERAGED BOD DAYS= 4. 1666668 E-02 HOURS= 1. 000000 -2. 00 0. 98 0. 94 -2. 00 0. 98 0. 95 0. 93 -2. 00 0. 97 0. 94 -2. 00 VERTICALLY AVERAGED BOD DAYS= 4. 1666668 E-02 HOURS= 1. 500000 -2. 00 0. 94 0. 92 -2. 00 0. 95 0. 93 0. 91 -2. 00 0. 94 0. 87 -2. 00

Visualization Using Excel • Import data, assign colors based on values • Slow! • Especially slow for time-based data • Solution: Program to automatically visualize data

Final Product • Jumping straight to the program that was created… • VB 6. 0

How was this created? • System Design – For speed, load all data into memory – Depth file: 2 D array – Time-based files: • Dictionary of 2 D arrays – Simpler than a 3 D array – Dictionary is like a dynamic, content-based vector

Dictionary Data Structure

System Architecture

Addressing Flicker • A screen update while cells are being redrawn for the next time step can result in unpleasant flicker • Use “Double Buffering” solution – Draw new cell colors on the hidden screen – Draw new vectors for velocities on the hidden screen – Copy entire hidden screen to the visible screen

Prototyping • Prototyping used since the client was not sure what they wanted • Somewhat fuzzy requirements led to some difficulties in implementation – Requirements changed • Had to add zoom, graphical slider synchronized with tide • Fortunately did not require major re-design – Wrong origin for vectors – Meticulously engineered code for arrowheads was thrown out

Schedule

Conclusion • Successfully delivered a visualization system for tidal basins • I learned: – More about programming in Visual Basic, particularly with graphics – Experience working with a real product as opposed to an academic exercise – More rigorous requirements could have eliminated some trouble and re-work farther into the development process