Identification_Information: Citation: Citation_Information: Originator: Arnell S. Forde Publication_Date: 2016 Title: Ground Penetrating Radar (GPR) Navigation Data Collected from Dauphin Island, Alabama in April 2013 Geospatial_Data_Presentation_Form: Tabular Digital Data Online_Linkage: pubs.usgs.gov/ds/0982/downloads/13BIM01_gps_data.zip Larger_Work_Citation: Citation_Information: Originator: Arnell S. Forde Originator: Christopher G. Smith Originator: Billy J. Reynolds Publication_Date: 2016 Title: Archive of Ground Penetrating Radar Data Collected During USGS Field Activity 13BIM01: Dauphin Island, Alabama, April 2013 Geospatial_Data_Presentation_Form: Publication (Other) Series_Information: Series_Name: U.S. Geological Survey Data Series Issue_Identification: 982 Publication_Information: Publication_Place: St. Petersburg, FL Publisher: U.S. Geological Survey Online_Linkage: pubs.usgs.gov/ds/0982 Description: Abstract: From April 13-20, 2013, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS-SPCMSC) conducted geophysical and sediment sampling surveys on Dauphin Island, Alabama as part of field activity number 13BIM01. This dataset, Ground Penetrating Radar (GPR) Navigation Data Collected from Dauphin Island, Alabama, in April 2013, contains the processed, differentially corrected position data obtained during this survey. Purpose: The objectives of this study were to quantify inorganic and organic accretion rates in back-barrier and mainland marsh and estuarine environments. Various field and laboratory methods were used to achieve these objectives, including subsurface imaging using Ground Penetrating Radar (GPR), sediment sampling, lithologic and microfossil analyses, and geochronology techniques to produce barrier island stratigraphic cross sections to help interpret the recent (last 2000 years) geologic evolution of the island. Supplemental_Information: Data were collected during USGS field activity 13BIM0. Additional survey details are available at http://cmgds.marine.usgs.gov/fan_info.php?fan=13BIM01. Funding for this survey was provided by the USGS Coastal and Marine Geology Program’s Barrier Island Evolution Research (BIER) project (http://coastal.er.usgs.gov/bier/). The post-processed Global Positioning System (GPS) data for this survey are provided in American Standard Code for Information Interchange (ASCII) format. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20130413 Ending_Date: 20130420 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -88.195013 East_Bounding_Coordinate: -88.074726 North_Bounding_Coordinate: 30.258131 South_Bounding_Coordinate: 30.243289 Keywords: Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: Ground Penetrating Radar (GPR) Theme_Keyword: navigation Theme_Keyword: location Theme_Keyword: Barrier Island Mapping Theme_Keyword: 13BIM01 Theme_Keyword: Global Positioning System (GPS) Place: Place_Keyword_Thesaurus: None Place_Keyword: United States of America Place_Keyword: Alabama Place_Keyword: Dauphin Island Place_Keyword: Mobile Bay Place_Keyword: Mississippi Sound Place_Keyword: Gulf of Mexico Access_Constraints: None. Please see “Distribution Info” for details. Use_Constraints: Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originators of the data in future products or derivative research. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey, Southeast Region Contact_Person: Arnell S Forde Contact_Position: Geologist Contact_Address: Address_Type: Mailing and Physical Address: 600 4th Street South City: St. Petersburg State_or_Province: FL Postal_Code: 33701 Contact_Voice_Telephone: 727-502-8111 Contact_Facsimile_Telephone: 727-502-8001 Contact_Electronic_Mail_Address: aforde@usgs.gov Native_Data_Set_Environment: Environment as of Metadata Creation: Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.2.2 (Build 3552) Service Pack N/A (Build N/A) Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: No formal attribute accuracy tests were conducted. Logical_Consistency_Report: No formal logical accuracy tests were conducted. Completeness_Report: A total of 65 GPR lines, representing a linear distance of approximately 40 km, were acquired during field activity 13BIM01. Due to acquisition errors encountered during the collection of lines 87 (missing GPS information) and 101 (incomplete data file), those files were not processed. No data were collected for lines 112, 113 and 114. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Location information associated with each GPR line was determined by post-processed differential correction using a base/rover setup. The field setup consisted of two (rover and base station) Ashtech ProFlex Global Navigation Satellite System (GNSS) receivers and antennas. The GNSS base and rover receivers recorded the raw full-carrier-phase positioning signals (L1/L2) from satellites, via Ashtech GNSS antenna, concurrently at 0.2 seconds (s) (5 Hertz [Hz]) intervals throughout the survey. The base station receiver was positioned on the National Geodetic Survey (NGS) published reference point NGS PID# BH1755 (Station ID: 8735180), located on the east side of the island, at the entrance to Fort Gaines. The vertical offset between the GNSS antenna and the NGS benchmark was 2.476 m. The rover GPS was mounted on a fixed frame above the GPR unit. The offset between the rover GNSS antenna (located on the GPR unit) and the ground was 1.915 m. Uncorrected positions were output from the rover GPS to the GPR as a National Marine Electronics Association (NMEA) GGA string at a 9600 baud rate. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: During acquisition of lines 66-116, the signal between the GPS rover unit and multiple satellites was interrupted or lost, most likely due to dense tree canopy within the survey area. This lack of communication with the satellites caused either incorrect values to be recorded or missing/incomplete GPS data to be collected. For lines missing post-processed GPS and (or) elevation data, elevation and location data were extracted from a topographic lidar survey, which was contracted by the USGS in July 2013 (Guy and Plant, 2013) and used instead. In cases where the DGPS data were incomplete or corrupted and lidar data were unavailable, non-elevation corrected profiles have been provided. Lines 65, 120, 121 and 122 were all processed using lidar-extracted location and elevation information. Lines 66-70, 74-82, 88, 92-94, 98, 100, 102, 109-116 and 124 have non-elevation corrected profile images associated with each line. Lineage: Process_Step: Process_Description: Navigation Acquisition: Location information associated with each GPR line was determined by post-processed differential correction using a base/rover setup. The field setup consisted of two (rover and base station) Ashtech ProFlex Global Navigation Satellite System (GNSS) receivers and antennas. The GNSS base and rover receivers recorded the raw full-carrier-phase positioning signals (L1/L2) from satellites, via Ashtech GNSS antenna, concurrently at 0.2 seconds (s) (5 Hertz [Hz]) intervals throughout the survey. The base station receiver was positioned on the National Geodetic Survey (NGS) published reference point NGS PID# BH1755 (Station ID: 8735180), located on the east side of the island, at the entrance to Fort Gaines. The vertical offset between the GNSS antenna and the NGS benchmark was 2.476 m. The rover GPS was mounted on a fixed frame above the GPR unit. The offset between the rover GNSS antenna (located on the GPR unit) and the ground was 1.915 m. Uncorrected positions were output from the rover GPS to the GPR as a National Marine Electronics Association (NMEA) GGA string at a 9600 baud rate. Process_Date: 20130413 Process_Step: Process_Description: Navigation processing: The coordinate values for the GNSS base station were checked using the time-weighted average of values obtained from the NGS On-Line Positioning User Service (OPUS). The average of the coordinates from all the occupations collected at the base during the survey did not differ significantly from the NGS published coordinates; therefore, the published coordinates were used for post-processing. The kinematic GNSS data from the GPR were post-processed using the concurrent GNSS data from the base station. The raw base station and rover data were imported into NovAtel GrafNav version 8.4 software and were post-processed by differential correction. During processing, steps were taken to ensure that the trajectories between the base and rover were clean, resulting in fixed positions. By analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GNSS session, data from satellites flagged by the program as having poor health or satellite time segments that had cycle slips could be excluded, or the satellite elevation mask angle could be adjusted to improve the position solutions. The final, differentially corrected, precise DGPS positions were computed at 1-s intervals for each roving GNSS session and exported in American Standard Code for Information Interchange (ASCII) text format (as a GGA string), which replaced the uncorrected real-time rover positions recorded during acquisition. The GPS data were acquired, processed, and exported in the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum. During acquisition of lines 66-116, the signal between the GPS rover unit and multiple satellites was interrupted or lost, most likely due to dense tree canopy within the survey area. This lack of communication with the satellites caused either incorrect values to be recorded or missing/incomplete GPS data to be collected. For lines missing post-processed GPS and (or) elevation data, elevation and location data were extracted from a topographic light detection and ranging (lidar) survey, which was contracted by the USGS in July 2013 and used instead. In cases where the DGPS data were incomplete or corrupted and lidar data were unavailable, non-elevation corrected profiles have been provided. Lines with post-processed GPS and elevation data issues are noted in this metadata file. Process_Date: 20140422 Overview_Description: Entity_and_Attribute_Overview: The entity and attribute information provided here describes the tabular data associated with the dataset. Entity_and_Attribute_Detail_Citation: The entity and attribute information was generated by the individual and (or) agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information. Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey, Southeast Region Contact_Person: Arnell S Forde Contact_Position: Geologist Contact_Address: Address_Type: Mailing and Physical Address: 600 4th Street South City: St. Petersburg State_or_Province: FL Postal_Code: 33701 Contact_Voice_Telephone: 727-502-8111 Contact_Facsimile_Telephone: 727-502-8001 Contact_Electronic_Mail_Address: aforde@usgs.gov Distribution_Liability: This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ASCII Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: pubs.usgs.gov/ds/0982/downloads/13BIM01_gps_data.zip Fees: None. No fees are applicable for obtaining the dataset. Metadata_Reference_Information: Metadata_Date: 20151222 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Arnell S Forde Contact_Organization: U.S. Geological Survey, Southeast Region Contact_Position: Geologist Contact_Address: Address_Type: Mailing and Physical Address: 600 4th Street South City: St. Petersburg State_or_Province: FL Postal_Code: 33701 Contact_Voice_Telephone: 727-502-8111 Contact_Facsimile_Telephone: 727-502-8001 Contact_Electronic_Mail_Address: aforde@usgs.gov Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998