GeoIS-EM Home         Mound sidescan sonar data processing, analysis and visualization

Helena Mitasova, Tom Drake, NCSU
Jessie McNinch, VIMS, Carl Miller, USACE

GIS data processing is performed for the USACE project: Monitoring Processes and the Fate of a Mixed-Sediment Mound at the Cape Fear River, NC
Mnoitoring data sets

Bald Head Island shore and bathymetry

a) Brunswick county DEM (30m resolution, USGS NED), mound is the little green spot south off the Bald Head Island
b) Bald Head Island LIDAR DEM, nearshore bathymetry from LARC data, channel and mound bathymetry from sonar.
c) Bald Head Island LIDAR DEM, nearshore bathymetry from LARC data in more detail, lines show the zero contours from both data sets.
d) 3D view of Bald Head Island and bathymetry with dredged channel
e) zoomed-in 3D view of the shore (LIDAR) and bathymetry (LARC)
f) View from the East

[IMG]a) [IMG] b) [IMG] c) [IMG]a) [IMG]b) [IMG]c)

DOER mound and the surrounding bathymetry

a) Bathymetry survey pattern b) Bathymetry in April 2001 and January 2002 c) Slope in April 2001 and January 2002
[bathymetry]a [bathymetry]b [slope]b

bathymetry: view from the NE (shore)

a) April 2001, b) January 2002
[IMG]a) [IMG]b)

High resolution (0.5m) mound change analysis

Orientation image for most of the views used in the analysis:

Summary statistics for the surfaces and their differences presented below. Size of the study area is 300 x 250 m

April 2001

a) given gridded data: 1m resolution
b) interpolated by RST with parameters preserving most of what is in data (minimal smoothing, resolution 0.5m)
c) interpolated and smoothed by RST
d) overlayed RST surfaces with and without smoothing, standard deviation is 0.11m, maximum difference is +1.33m (see Summary statistics )

[IMG]a) [IMG]b) [IMG]c) [IMG]d) Legend legend

Note: the visible rectangles show area with insufficient data coverage - the elevation differences between segments indicate the level of uncertainty.

January 2002


a) RST interpolated surface from January 2002 (minimal smoothing, resolution 0.5m)
b) interpolated and smoothed by RST
c) overlayed RST surfaces with and without smoothing.

[IMG]a) [IMG]b) [IMG]c) Legend legend

Comparison between April 2001 and January 2002

a) Both surfaces overlayed: orange is Apr. 01, blue is Jan. 02
b) Crossections of the two overlayed surfaces

[IMG] a [IMG] b [IMG] b [IMG] b [IMG] b [IMG] b

Difference draped over Apr. 01 surface: yellow-red is loss, cyan-blue is gain.
Mean loss was 0.23m while mean gain was 0.24m. The maximum height of the mound was reduced only from -6.4 to -6.7m (around 0.3m), based on the given data, or -6.6 to -7.2 (around 0.6m) based on the smoothed surfaces. The difference between "raw" surfaces is <-1.7, +1.7m>, with net volume difference 8380 cubic m gain mostly on NE side of the mound. The difference between smoothed surfaces is <-1.1, +0.8> with net volume difference 8540 cubic m. Slope was reduced from <0.,9.> degrees to <0.,6.> degrees.

[IMG]a [IMG]b [IMG]c Legend legend

This project is supported by Army Research Office and National Research Council


Processed and visualized
by GRASS5