Link to USGS Home Page

Prepared in cooperation with the Iowa Department of Natural Resources

Bathymetric Contour Maps for Lakes Surveyed in Iowa in 2003

By S. Mike Linhart and Kris D. Lund

U.S. Geological Survey Scientific Investigations Map 2933

AVAILABLE ONLINE ONLY


Individual Target Data-Collection Points for Easter Lake, Polk County, Iowa

Metadata also available as

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator:
U.S. Geological Survey, Iowa Water Science Center, Eastern Iowa Field Unit, Iowa City, Iowa
Publication_Date: 2006
Title:
Individual Target Data-Collection Points for Easter Lake, Polk County, Iowa
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: Scientific Investigations Map 2933-B
Publication_Information:
Publisher: U.S. Geological Survey
Online_Linkage: None
Description:
Abstract:
Point coverage of bathymetry target points for Easter Lake in Polk Co., Iowa. The U.S. Geological Survey conducted a bathymetric survey of Easter Lake in 2003.
Purpose:
This digital, geographically referenced data set was developed by the U.S. Geological Survey to be used with the Lake Bathymetric project, Eastern Field Unit, Iowa City, Iowa.
Supplemental_Information:
Present limitations of the data-collection equipment restrict data collection to depths greater than approximately 3.3 feet. For areas that were too shallow to profile or that were congested with debris, depths were collected manually along with a corresponding GPS location. The target point depths were converted to elevation and input into a geographic information system (GIS) software package, ArcInfo, to create a point coverage representing discrete point locations. This point coverage was one of three point coverages used to generate a three-dimensional surface representing the lake-bottom elevation.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2003
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -93.580959
East_Bounding_Coordinate: -93.549466
North_Bounding_Coordinate: 41.546791
South_Bounding_Coordinate: 41.534364
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Lakes
Theme_Keyword: Bathymetry
Theme_Keyword: Inland Waters
Theme_Keyword: Hydrology
Theme_Keyword: USGS
Place:
Place_Keyword: Iowa
Access_Constraints:
This digital, geographically referenced data set was developed by the U.S. Geological Survey to be used with the Lake Bathymetric project, Eastern Field Unit, Iowa City, Iowa.
Use_Constraints:
The data are released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Greg Nalley
Contact_Position: Project Chief - Eastern Field Unit Supervisory Hydrologist
Contact_Voice_Telephone: 319-337-4191
Contact_Facsimile_Telephone: 319-358-3606
Contact_Electronic_Mail_Address: gmnalley@usgs.gov
Native_Data_Set_Environment:
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.722

Data_Quality_Information:
Completeness_Report:
Point coverage of bathymetry target points collected in areas of the lake where it was too shallow to collect bathymetry data using the 200-KHz transducer.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Accuracy is tested by visual comparison of source with digital data on an interactive computer system.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Type_of_Source_Media: computer program
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2003
Source_Currentness_Reference: ground condition
Process_Step:
Process_Description:
Data collection: Bathymetry data were collected using the Bathymetric Survey System (BSS+5) with a 200-kHZ intelligent depth sounder (IDS) and a differential GPS (Novatel DGPS beacon or omnistar receiver) (Specialty Devices, Inc., 2003, Bathymetric Survey System BSS+5 with omnistar manual: Specialty Devices, Inc., Plano, Texas, 38 p.). The differential GPS has a horizontal accuracy of less than 1 meter (3.281 ft). Bathymetry data were collected and stored in Hypack Max software (ver. 2.12a) (Hydrographic Survey Software, User's Manual, Hypack Max, Coastal Oceanographics, Inc., Middlefield, Conn.). In Hypack Max, the geodetic parameters were set to UTM north, Zone 15, and ellipsoid GRS-1980. Distance (easting and northing) and depth units were both collected in feet.

A bar check calibration on the echo sounder was performed at the start of each day following established protocols (U.S. Army Corps of Engineers, 1994, Engineering and design: Hydrographic survey EM 1110-2-1003, chap. 9-3, p. 9-4 to 9-9). This was done to ensure that the echo sounder was calibrated correctly. The bar check involves suspending a 2-ft-diameter flat aluminum plate directly below the echo sounder. The suspension line is marked in 5-ft increments. An initial calibration is made at 5 ft by entering the speed of sound in water (based on water temperature) and then adjusting the offset of the transducer in the computer software. The offset is the draft of the transducer below the lake surface. The aluminum plate is then lowered in 5-ft increments (depending on the range of depths expected to be encountered on the day of data collection) and adjustments in the speed of sound are made until depth readings and the depth of the aluminum plate agree to within approximately 0.1 ft.

Data were collected along viewable planned transect lines that were set-up in Hypack Max using the internal line editor prior to data collection. Transect lines were spaced at 50-ft intervals perpendicular to the long axis of Easter Lake. Depending on boat speed, one bathymetry data point was collected at approximately 4- to 8-ft intervals. Data points may be much closer in areas where transect or perimeter runs overlap. Perimeter bathymetry data points were collected while driving the boat around the perimeter of the lake. Target points were collected in areas of the lake where it was too shallow to collect data with the BSS+5 system. Target point depths were collected manually along with a corresponding easting and northing location. The number and location of target points were based on a judgment made in the field that was thought to be spatially representative of the area. In addition, shore point locations (easting and northing) were collected to define the edge of the lake. These locations were collected by touching the bow of the boat to the shoreline at various intervals along the shoreline and recording the position using a bow-mounted GPS antenna.

The water-surface elevation of Easter Lake was determined by tape down (using a steel tape) from a reference point (with a known elevation) on the north rim of a manhole located on top of the concrete emergency spillway west of the main spillway. The elevation of the reference point, according to the Polk County Engineers Office (oral commun., 2003), was 816.85 ft above NGVD29. The water-surface elevation was found to be 813.0 ft above NGVD29 on July 30, 2003.

Post-processing: Bathymetry data were processed back in the office using the Hypack Max software. Post-processing involved removing obvious spikes, inputting depths for the time-tagged target points, and editing extraneous points within the shore point files. In addition, tide corrections were applied in Hypack Max to convert depths to elevations. The processed bathymetry data in Hypack Max were exported to XYZ format. A total of three separate files were exported into XYZ format: (1) transect and perimeter bathymetric data; (2) shore point location data; (3) and the target point data. All three XYZ files were then converted to ASCII text files for input into ESRI-ArcGIS (ver. 8.3).

Generation of Bathymetry Map: The output text files (containing northing, easting, and elevation) were input into an arc macro language (AML) script called createpoint in ARC to generate three corresponding coverages (eas_allpts, eas_edgepts, and eas_targpts). Projections for the coverages were then defined in ARC as UTM zone 15, NAD83, and units in feet.

In ARC, the eas_allpts coverage was processed through the WEEDPOINT command with a weed-tolerance of 30 ft to create the output coverage eas_tinpts30. Of the original 14,934 data points, 3,038 data points remained after weeding. The weeding was performed to reduce the density of points in one direction (along data-collection transects) to minimize the spatial pull of contours toward the densified lines. The eas_tinpts30 coverage was then input into a TIN model.

The point coverage eas_ptsinterp was created using an arc macro language (AML) script. The script interpolated additional data points between bathymetry data points collected in the field. Data points were interpolated along creek channels and within lake coves to aid in generating contours.

To generate contours and calculate lake volume, three-dimensional surfaces (TIN models) were created using 3-D Analyst in ArcMap. The TIN eas_tin30 was used to generate the preliminary contours. The TIN model (eas_tin30) was generated using the eas_tinpts30, eas_targpts, and eas_ptsinterp point coverages triangulated as mass points. Height source was "elevation". The eas_bndelev and eas_islelev line coverages were input as hard lines with height source as "elev" (elevation value = 813.0 ft). The eas_bndry polygon coverage was input as a hard clip to clip the TIN to the lake shoreline. The eas_island polygon coverage was input as a hard erase to remove the island from the TIN. Another TIN model (eas_tin) was later generated to further adjust contours and to calculate lake volume after the boundary coverages (eas_bndry and eas_bndelev) were adjusted using the DOQ.


Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: Entity point
Point_and_Vector_Object_Count: 49
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: Point
Point_and_Vector_Object_Count: 4

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Transverse Mercator
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999600
Longitude_of_Central_Meridian: -93.000000
Latitude_of_Projection_Origin: 0.000000
False_Easting: 1640416.666667
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.000005
Ordinate_Resolution: 0.000005
Planar_Distance_Units: survey feet
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: National Geodetic Vertical Datum of 1929
Altitude_Distance_Units: feet
Depth_System_Definition:
Depth_Datum_Name: Mean sea level
Depth_Distance_Units: feet

Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: eas_targpts.pat
Attribute:
Attribute_Label: FID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: AREA
Attribute_Definition: Area of feature in internal units squared.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Area is always zero for point coverages. Values are automatically generated.
Attribute:
Attribute_Label: PERIMETER
Attribute_Definition: Perimeter of feature in internal units.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Perimeter is always zero for point coverages. Values are automatically generated.
Attribute:
Attribute_Label: EAS_TARGPTS#
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: EAS_TARGPTS-ID
Attribute_Definition: User-defined feature number.
Attribute_Definition_Source: ESRI
Attribute:
Attribute_Label: EASTING
Attribute:
Attribute_Label: NORTHING
Attribute:
Attribute_Label: ELEVATION

Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:
Lake Bathymetric Project, U.S. Geological Survey, Iowa City, Iowa
Contact_Person: Greg Nalley
Contact_Position: Project Chief
Contact_Address:
Address_Type: mailing address
Address: P.O. Box 1230
City: Iowa City
State_or_Province: Iowa
Postal_Code: 52244
Country: USA
Contact_Voice_Telephone: 319-337-4191
Contact_Facsimile_Telephone: 319-358-3606
Contact_Electronic_Mail_Address: gmnalley@usgs.gov
Resource_Description: None
Distribution_Liability:
The Lake Bathymetric project of the Eastern Field Unit, the Water Resources Discipline (WRD), and the U.S. Geological Survey make no guarantee nor offer any warranty concerning the accuracy, condition, or application of the information contained in these geographic data.

The burden for determining fitness for use of this data lies entirely with the user. Although these data have been processed successfully on computers of WRD, no warranty, expressed or implied, is made by WRD regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty.

In no event shall the WRD have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of the delivery, installation, operation, or support by WRD.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Transfer_Size: 0.027

Metadata_Reference_Information:
Metadata_Date: 20060724
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Mike Linhart
Contact_Position: Hydrologist
Contact_Address:
Address_Type: mailing address
Address: P.O. Box 1230
City: Iowa City
State_or_Province: Iowa
Postal_Code: 52244
Country: USA
Contact_Voice_Telephone: 319-337-4191
Contact_Facsimile_Telephone: 319-358-3606
Contact_Electronic_Mail_Address: slinhart@usgs.gov
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Access_Constraints: None
Metadata_Use_Constraints: None
Metadata_Extensions:
Online_Linkage: <http://www.esri.com/metadata/esriprof80.html>
Profile_Name: ESRI Metadata Profile

Generated by mp version 2.8.6 on Mon Jul 24 15:11:55 2006

Back