Old Dominion University

Summer Research Progress: Week 1 – Hydrology, the Fourier Transform, and Spectrograms

George FavaDepartment of Electrical and Computer Engineering

Temple UniversityURL:

Old Dominion University: Slide 2

Indian Creek Modeling

Hydrology is the study of the movement and distribution of water throughout the Earth(http://en.wikipedia.org/wiki/Hydrology)

• Dr. Boufadel’s data, chair of the Civil Engineering department

•Raw data was non-uniformly spaced

•Interpolation of data using the Nearest Neighbor approach

• 3-D Mesh plots were generated to visual the contours of the data

Old Dominion University: Slide 3

Testing of MATLAB’s Interpolation Methods

Linear Cubic Nearest Neighbor

Old Dominion University: Slide 4

Extraction of Data from the Mesh Plot

• Zero and Ninety degree lines were drawn through the origin of the 3-D Nearest Neighbor Mesh plot

Old Dominion University: Slide 5

Extraction of Data from the Mesh Plot

• Z-axis or “Height” data was extracted from these lines and was used as inputs for the Fourier Transform

(Zero degree data from left to right) (Ninety degree data from bottom to top)

Old Dominion University: Slide 6

Extraction of Data from the Mesh Plot

• “Fast” Fourier Transform of the Z-axis data using

• Magnitude plots of the data are shown to visual the frequency content

Old Dominion University: Slide 7

Line Data Summary

Old Dominion University: Slide 8

Audio Spectrogram

• Spectrograms measure the spectral density of a signal

• It works by using a short-time Fourier Transform over small chunks, or windows, of data

• The spectrogram shows:

• time on the x-axis

• the frequency value on the y-axis

• the intensity or density of the frequencies using color for the third dimension