A Visualization System for Tidal Basins

1. A Visualization System for Tidal Basins Kenrick Mock CS 470

2. 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

3. Data Files • Area of interest divided into 2D 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

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

5. Data File Format • All files are in text • Depth file example • Mapping -99.00 -99.00 3.96 3.96 -99.00 3.96 3.96 3.96 -99.00 3.96 3.96 -99.0

6. Time-Based Files • Typically 2-5Mb in size • Value of each cell specified for a time period VERTICALLY AVERAGED BOD DAYS= 2.0833334E-02 HOURS= 0.5000000 -2.00 -2.00 1.00 1.00 -2.00 1.00 1.00 1.00 -2.00 1.00 1.00 -2.00 VERTICALLY AVERAGED BOD DAYS= 4.1666668E-02 HOURS= 1.000000 -2.00 -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= 4.1666668E-02 HOURS= 1.500000 -2.00 -2.00 0.94 0.92 -2.00 0.95 0.93 0.91 -2.00 0.94 0.87 -2.00

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

8. Final Product • Jumping straight to the program that was created… • VB 6.0

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

10. Dictionary Data Structure

11. System Architecture

12. Addressing Flicker • A screen update while cells are being re-drawn 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

13. 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

14. Schedule

15. 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