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Detailed descriptions of how we do what we do. Find information on equipment, survey procedures, post-processing, and mapping techniques. Photos are also included.
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Methods
Coring Equipment
Core Sample
The Kansas Biological Survey (KBS) operates a Specialty Devices Inc. sediment vibracorer mounted on a dedicated 24' pontoon boat. The vibracorer uses 3" diameter aluminum thinwall pipe in user-specified lengths (KBS has used up to 10' sections). The vibracorer runs off 24-volt batteries, and uses an electric motor with counter-rotating weights in the vibracorer head unit to create a high-frequency vibration in the pipe, allowing the pipe to penetrate even solidly packed sediments and substrate as it is lowered into the lake using a manually operated winch system.
Procedures
Once the open end of the core pipe has penetrated to the substrate, the unit is turned off and the unit is raised to the surface using the winch. At the surface, the pipe containing the sediment core is disconnected from the vibracore head for further onboard processing. The sediment core can be cut into sections while in the pipe, the pipe bisected longitudinally for taking samples along the length of the core, or the sediment can be manually extruded from the pipe and measured.
Specifications from the Kansas Water Office, relayed from the US Army Corps of Engineers Tulsa District help determine the appropriate position, number, size, thickness, and length of core samples.
Equipment
The Kansas Biological Survey (KBS) runs a Biosonics DT-X acoustic echosounding system with a 20 kHz split-beam transducer and 38 kHz single beam transducer. Latitude-longitude information is provided by a JRC global positioning system (GPS) that interfaces with the Biosonics system. ESRI's ArcGIS is used for on-lake navigation and positioning, with GPS data feeds provided by the Biosonics unit through a serial code. Power is provided to the echosounding unit, command/navigation computer, and auxilary monitor by means of a Yamaha generator.
Pre-Survey Preparation
Prior to conducting the survey, geospatial data of the target lake is acquired, including geoferenced National Agricultural Imagery Project (NAIP) photography. The lake boundary is digitized as a polygon shapefile from FSA NAIP georeferenced aerial photography obtained online from the Data Access and Service Center (DASC) at the Kansas Geological Survey.
Establishment of lake levels
Lake levels are obtained from the US Army Corps of Engineers at the beginning of each day.
Calibration (Temperature and Ball Check)
After boat launch and initialization of the Biosonics system and command computer, system parameters are set in the Biosonics Visual Acquisition software. The temperature of the lake at 1-2 meters is taken with a research-grade Clinefinder metric electronic thermometer. This temperature, in degrees Celsius, is input to the Biosonics Visual Acquisition software to calculate the speed of sound in water at the given temperature at the given depth. Start range, end range, ping duration, and ping interval are also set at this time.
A ball check is performed using a tungsten-carbide sphere supplied by Biosonics for this purpose with each transducer. The ball is lowered to a known distance below the transducer face. The position of the ball in the water column (distance from the transducer face to the ball) is clearly visible on the echogram. The echogram distance is compared to the known distance to assure that parameters are properly set and the system is operating correctly. Ball checks are performed at any time the system is stopped and restarted.
Survey Procedures
Transect lines are followed. Using the GPS Extension of ArcGIS, the GPS data feed from the GPS receiver via the Biosonics echosounder, and the pre-planned transect pattern, the location of the boat on the lake in real-time is shown on the command/navigation computer screen. To assist the boat operator in navigation, an auxilary LCD monitor is connected to the computer and placed within the easy view of the boat operator. Transducer face depth is 0.5 meters below the water surface. Data are automatically logged in new files every half-hour (apporximately 9000 ping files) by the Biosonics system.
Post-processing (Visual Bottom Typer)
The Biosonics DT-X system produces data files in a proprietary DT4 file format containing acoustic and GPS data. To extract the bottom position from the acoustic data, each DT4 file is processed through the Biosonics Visual Bottom Typer (VBT) software. The processing algorithm is described as follows:
"The Biosonics, Inc. bottom tracker is an "end-up" algorithm, in that it begins searching for the bottom echo portion of a ping from the last sample toward the first sample. The bottom tracker tracks the bottom echo by isolating the region(s) where the data exceeds a peak threshold for N consecutive samples, then drops below a surface threshold of M samples. once a bottom echo has been identified, a bottom sampling window is used to find the next echo. The bottom echo is first isolated by user-defined threshold values that indicate (1) the lowestenergy to include in the bottom echo (bottom detection threshold) and (2) the lowest energy to start looking for a bottom peak (peak threshold). The bottom detection threshold allows the user to filter out noise caused by a low data acquisition threshold. The peak threshold prevents the algorithm from identifying the small energy echos (due to fish, sediment, plant life) as a bottom echo." (Biosonics Visual Bottom Typer User's Manual, Version 1,10, p. 70).
Data is output as a comma-delimited (*.csv) text file. A set number of qualifying pings are averaged to produce a single report (for example, the output for ping 31 {when pings per report is 20} is the average of all values for pings 12-31).
Post-processing (ArcGIS)
Ingest to ArcGIS is accomplished by using the Tools - Add XY Data option. The projection information is specified at this time (WGS84). Files are displayed as Event files, and can be exported as shapefiles if desired. Typically, Event files are merged using the ArcGIS command Data Management Tools - Genreal - Merge, and the output from this is a shapefile.
Initial QA/QC is performed next. The point shapefile(s) is visually evaluated for any points with spurious lat/lon coordinates, which should be obvious (and unlikely). The attribute table is examined for any points reporting a value of 0 in the depth file, and these points are delted. Any points with a value less than the start range of the data acquisition parameter are deleted. In the attribution table, the adjustment for transducer depth is performed next. A new file - AdjDepth - is added to the attribute table of the point shapefile. The value for AdjDepth is calculated as AdjDepth = Depth + (Transducer Face Depth), where the Transducer Face Depth represents the depth of the transducer face below water level in meters.
To set depths relative to the lake elevation, another field is added to the attribute table of the point shapefile, Depth_Elev. The value for this attribute is then computed as Depth_Elev = (Elevation of the Water Surface) - Adj_Depth. The lake surface elevation for each survey date was used for each data set collected on that date. Thus, all depth measurements are expressed as the elevation of the lake bottom, which then allows all data files to be combined into a master file for an entire lake.
A triangulated irregular network (TIN) was created using the master depth data point shapefile and the lake polygon shapefile with the lake surface elevation. Output projection is typically specified to be the same as the input data. Raster interpolation of the point data is also performed using the same input data and the Topo to Raster option within the 3D Extension of ArcGIS. Following creation of the TIN file and the raster file, any necessary projections or conversions from meters to feet units are performed.
The Kansas Biological Survey (KBS) runs a Biosonics DT-X acoustic echosounding system with a 20 kHz split-beam transducer and 38 kHz single beam transducer. Latitude-longitude information is provided by a JRC global positioning system (GPS) that interfaces with the Biosonics system. ESRI's ArcGIS is used for on-lake navigation and positioning, with GPS data feeds provided by the Biosonics unit through a serial code. Power is provided to the echosounding unit, command/navigation computer, and auxilary monitor by means of a Yamaha generator.
Pre-Survey Preparation
Prior to conducting the survey, geospatial data of the target lake is acquired, including geoferenced National Agricultural Imagery Project (NAIP) photography. The lake boundary is digitized as a polygon shapefile from FSA NAIP georeferenced aerial photography obtained online from the Data Access and Service Center (DASC) at the Kansas Geological Survey.
Establishment of lake levels
Lake levels are obtained from the US Army Corps of Engineers at the beginning of each day.
Calibration (Temperature and Ball Check)
After boat launch and initialization of the Biosonics system and command computer, system parameters are set in the Biosonics Visual Acquisition software. The temperature of the lake at 1-2 meters is taken with a research-grade Clinefinder metric electronic thermometer. This temperature, in degrees Celsius, is input to the Biosonics Visual Acquisition software to calculate the speed of sound in water at the given temperature at the given depth. Start range, end range, ping duration, and ping interval are also set at this time.
A ball check is performed using a tungsten-carbide sphere supplied by Biosonics for this purpose with each transducer. The ball is lowered to a known distance below the transducer face. The position of the ball in the water column (distance from the transducer face to the ball) is clearly visible on the echogram. The echogram distance is compared to the known distance to assure that parameters are properly set and the system is operating correctly. Ball checks are performed at any time the system is stopped and restarted.
Survey Procedures
Transect lines are followed. Using the GPS Extension of ArcGIS, the GPS data feed from the GPS receiver via the Biosonics echosounder, and the pre-planned transect pattern, the location of the boat on the lake in real-time is shown on the command/navigation computer screen. To assist the boat operator in navigation, an auxilary LCD monitor is connected to the computer and placed within the easy view of the boat operator. Transducer face depth is 0.5 meters below the water surface. Data are automatically logged in new files every half-hour (apporximately 9000 ping files) by the Biosonics system.
Post-processing (Visual Bottom Typer)
The Biosonics DT-X system produces data files in a proprietary DT4 file format containing acoustic and GPS data. To extract the bottom position from the acoustic data, each DT4 file is processed through the Biosonics Visual Bottom Typer (VBT) software. The processing algorithm is described as follows:
"The Biosonics, Inc. bottom tracker is an "end-up" algorithm, in that it begins searching for the bottom echo portion of a ping from the last sample toward the first sample. The bottom tracker tracks the bottom echo by isolating the region(s) where the data exceeds a peak threshold for N consecutive samples, then drops below a surface threshold of M samples. once a bottom echo has been identified, a bottom sampling window is used to find the next echo. The bottom echo is first isolated by user-defined threshold values that indicate (1) the lowestenergy to include in the bottom echo (bottom detection threshold) and (2) the lowest energy to start looking for a bottom peak (peak threshold). The bottom detection threshold allows the user to filter out noise caused by a low data acquisition threshold. The peak threshold prevents the algorithm from identifying the small energy echos (due to fish, sediment, plant life) as a bottom echo." (Biosonics Visual Bottom Typer User's Manual, Version 1,10, p. 70).
Data is output as a comma-delimited (*.csv) text file. A set number of qualifying pings are averaged to produce a single report (for example, the output for ping 31 {when pings per report is 20} is the average of all values for pings 12-31).
Post-processing (ArcGIS)
Ingest to ArcGIS is accomplished by using the Tools - Add XY Data option. The projection information is specified at this time (WGS84). Files are displayed as Event files, and can be exported as shapefiles if desired. Typically, Event files are merged using the ArcGIS command Data Management Tools - Genreal - Merge, and the output from this is a shapefile.
Initial QA/QC is performed next. The point shapefile(s) is visually evaluated for any points with spurious lat/lon coordinates, which should be obvious (and unlikely). The attribute table is examined for any points reporting a value of 0 in the depth file, and these points are delted. Any points with a value less than the start range of the data acquisition parameter are deleted. In the attribution table, the adjustment for transducer depth is performed next. A new file - AdjDepth - is added to the attribute table of the point shapefile. The value for AdjDepth is calculated as AdjDepth = Depth + (Transducer Face Depth), where the Transducer Face Depth represents the depth of the transducer face below water level in meters.
To set depths relative to the lake elevation, another field is added to the attribute table of the point shapefile, Depth_Elev. The value for this attribute is then computed as Depth_Elev = (Elevation of the Water Surface) - Adj_Depth. The lake surface elevation for each survey date was used for each data set collected on that date. Thus, all depth measurements are expressed as the elevation of the lake bottom, which then allows all data files to be combined into a master file for an entire lake.
A triangulated irregular network (TIN) was created using the master depth data point shapefile and the lake polygon shapefile with the lake surface elevation. Output projection is typically specified to be the same as the input data. Raster interpolation of the point data is also performed using the same input data and the Topo to Raster option within the 3D Extension of ArcGIS. Following creation of the TIN file and the raster file, any necessary projections or conversions from meters to feet units are performed.
1957 John Redmond Digital Elevation Model
(Example drawn from 2007 John Redmond Survey)
Note: Caution should be exercised in drawing conclusions based on comparison between two maps of different scales, dates, and production methods.
A pre-impoundment topographic map dated 1957 with a contour interval of five feet (5') was obtained in digital form from the Corps of Engineers Tulsa District Office via the Kansas Water Office. The map was converted from PDF format to TIFF format at 300dpi and georeferenced to the Universal Transverse Mercator (UTM) projection, NAD83, Zone 15, in ERDAS Imagine image processing software. A total of fifty (50) control points were located on the 1957 Corps map at section corners and referenced to corresponding locations on a UTM-georeferenced USGS Digital Raster Graphic (DRG) topographic map. A second-order polynomial transformation was computed from the 50 coordinate pairs and the 1957 map was resampled to the UTM coordinate system using a nearest-neighbor algorithm with an output pixel size of three (3) meters.
Contour lines were manually digitized to a polyline shapefile and attributed. Per the direction of the Kansas Water Office, all contour intervals at elevations 1050 feet and below were digitized (every five feet of vertical); above the 1050-foot elevation, every other contour interval was digitized (every ten feet of vertical). Lines representing streams were digitized as a separate polyline shapefile, and spot locations of elevation appearing on the map (benchmarks and high water marks) were digitized as a point shapefile.
The contour line file, the stream line file, and the spot elevation point file were input to the TIN tool in ArcGIS. The TIN tool uses the contour line file and the spot elevation file to establish elevations within a triangulated irregular network, while the stream line file is used as a breakline to "force" valley bottoms to their "true" locations. The TIN file was then converted to a raster file to facilitate compairon elevations with the 2007 bathymetric data (present-day lake bottom elevations).
Changes in lake bottom elevation between 1957 and 2007 were computed by digitally subtracting the 1957 digital elevation model from the 2007 digital elevation model. Negative numbers on the resulting ouput indicate loss of material during the 50-year period; positive numbers indicate accumulated material (siltation). The difference map suggests that the greatest sedimentation has occured in the former river channel, as might be expected; furthermore, the majority of the non-river channel silt accumulation has occured in the lower part of the reservoir. Some loss of material has occured in the 50-year period, principally along the northern lake shore (possible shoreline erosion) and just offshore of the park at the north end of the dam (possible material removal during construction).
Note: Caution should be exercised in drawing conclusions based on comparison between two maps of different scales, dates, and production methods.
A pre-impoundment topographic map dated 1957 with a contour interval of five feet (5') was obtained in digital form from the Corps of Engineers Tulsa District Office via the Kansas Water Office. The map was converted from PDF format to TIFF format at 300dpi and georeferenced to the Universal Transverse Mercator (UTM) projection, NAD83, Zone 15, in ERDAS Imagine image processing software. A total of fifty (50) control points were located on the 1957 Corps map at section corners and referenced to corresponding locations on a UTM-georeferenced USGS Digital Raster Graphic (DRG) topographic map. A second-order polynomial transformation was computed from the 50 coordinate pairs and the 1957 map was resampled to the UTM coordinate system using a nearest-neighbor algorithm with an output pixel size of three (3) meters.
Contour lines were manually digitized to a polyline shapefile and attributed. Per the direction of the Kansas Water Office, all contour intervals at elevations 1050 feet and below were digitized (every five feet of vertical); above the 1050-foot elevation, every other contour interval was digitized (every ten feet of vertical). Lines representing streams were digitized as a separate polyline shapefile, and spot locations of elevation appearing on the map (benchmarks and high water marks) were digitized as a point shapefile.
The contour line file, the stream line file, and the spot elevation point file were input to the TIN tool in ArcGIS. The TIN tool uses the contour line file and the spot elevation file to establish elevations within a triangulated irregular network, while the stream line file is used as a breakline to "force" valley bottoms to their "true" locations. The TIN file was then converted to a raster file to facilitate compairon elevations with the 2007 bathymetric data (present-day lake bottom elevations).
Changes in lake bottom elevation between 1957 and 2007 were computed by digitally subtracting the 1957 digital elevation model from the 2007 digital elevation model. Negative numbers on the resulting ouput indicate loss of material during the 50-year period; positive numbers indicate accumulated material (siltation). The difference map suggests that the greatest sedimentation has occured in the former river channel, as might be expected; furthermore, the majority of the non-river channel silt accumulation has occured in the lower part of the reservoir. Some loss of material has occured in the 50-year period, principally along the northern lake shore (possible shoreline erosion) and just offshore of the park at the north end of the dam (possible material removal during construction).