Alaska coastal shorelines and shoreline change statistics for the community of Scammon Bay

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Frequently anticipated questions:


What does this data set describe?

Title:
Alaska coastal shorelines and shoreline change statistics for the community of Scammon Bay
Abstract:
The Division of Geological & Geophysical Surveys has (1) delineated past shoreline positions fronting Alaska communities using orthorectified historically and recently collected aerial imagery, (2) computed rates of shoreline change along cross shore transects cast approximately every 50 meters along the delineated shorelines using the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009), and (3) summarized the results for each community in the region. This geodatabase for the community of Scammon Bay includes shoreline positions, shoreline envelopes, and community location identifiers, as well as geodatabase tables of shoreline change statistics, shoreline change analysis transect information, and summary shoreline change statistics.
  1. How should this data set be cited?

    Glenn, R. J., and Overbeck, J.R., 2018, Alaska coastal shorelines and shoreline change statistics for the community of Scammon Bay: Alaska Division of Geological & Geophysical Surveys, Anchorage, Alaska, United States.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -165.658226
    East_Bounding_Coordinate: -165.545277
    North_Bounding_Coordinate: 61.864048
    South_Bounding_Coordinate: 61.844239

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1955
    Ending_Date: 2015
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a vector data set.

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 3
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -165
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0001
      Ordinates (y-coordinates) are specified to the nearest 0.0001
      Planar coordinates are specified in Meters

      The horizontal datum used is World Geodetic System of 1984.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563000025.

  7. How does the data set describe geographic features?

    SCAMMONBAY
    point file with community name, location, profile location, compiler, and date range of shoreline imagery. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    SCAMMONBAY_DSAS_Intersect_Table
    The DSAS Transect Intersect table gives the X and Y coordinates of each intersection between the shorelines and transects. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    TransectID
    Unique identifier for transect intersecting with the shorelines. (Source: this study)

    Integer

    BaselineID
    Unique identifier for which baseline segment the transect was cast from. (Source: this study)

    Integer

    ShorelineID
    Date of the shoreline the transect is intersecting. (Source: this study)

    String

    Distance
    Distance from the baseline to the intersection for the shoreline from a single date. (Source: this study)

    Double

    IntersectX
    X coordinate of intersection. (Source: this study)

    Double

    IntersectY
    Y coordinate of intersection. (Source: this study)

    Double

    SCAMMONBAY_DSAS_Rates_Table
    Each method used to calculate shoreline rates of change is based on measured differences between shoreline positions through time. The reported rates are expressed as meters of change along transects per year. When the user-selected rate-change calculations are processed, DSAS merges the individual module calculations, and the output is made available as a table in ArcMap. The rate-change statistics provided with DSAS have the standardized field headings, listed below (Himmelstoss, 2009). Some of the shoreline statistic values listed below require greater than 3 shoreline positions to calculate the statistic. If the shoreline statistic is a null value, there were not enough shorelines analyzed to compute that statistic. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    TransectId
    Unique identifier for transect intersecting with the shorelines. (Source: this study)

    Integer

    TCD
    Total cumulative distance of shoreline alongshore in meters. (Source: this study)

    Double

    EPR
    The end point rate is calculated by dividing the distance of shoreline movement by the time elapsed between the oldest and the most recent shoreline (Himmelstoss, 2009). (Source: this study)

    Double

    ECI
    Confidence Interval of Endpoint Rate (Source: this study)

    Double

    SCE
    The shoreline change envelope reports a distance, not a rate. The SCE is the distance between the shoreline farthest from and closest to the baseline at each transect in meters. This represents the total change in shoreline movement for all available shoreline positions and is not related to their dates (Himmelstoss, 2009). (Source: this study)

    Double

    NSM
    The net shoreline movement reports a distance, not a rate. The NSM is associated with the dates of only two shorelines. It reports the distance between the oldest and youngest shorelines for each transect in meters (Himmelstoss, 2009). (Source: this study)

    Double

    LMS
    In ordinary and weighted least-squares regression, the best-fit line is placed through the points in such a way as to minimize the sum of the squared residuals. In the linear regression method, the sample data are used to calculate a mean offset, and the equation for the line is determined by minimizing this value so that the input points are positioned as close to the regression line as possible. In the least median of squares method the median value of the squared residuals is used instead of the mean to determine the best-fit equation for the line. This method is a more robust regression estimator that minimizes the influence of an anomalous outlier on the overall regression equation. The Least Median of Squares rate is the slope of this best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WLR
    In a weighted linear regression, more reliable data are given greater emphasis or weight towards determining a best-fit line. In the computation of rate-of-change statistics for shorelines, greater emphasis is placed on data points for which the position uncertainty is smaller. The Weighted Linear Regression Rate is the slope of that best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WR2
    R-squared of Weighted Linear Regression (Source: this study)

    Double

    WSE
    Standard Error of Linear Regression (Source: this study)

    Double

    WCI90
    Confidence Interval of Weighted Linear Regression (Source: this study)

    Double

    LRR
    A linear regression rate-of-change statistic can be determined by fitting a least-squares regression line to all shoreline points for a particular transect. The regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The Linear Regression Rate is the slope of that line (Himmelstoss, 2009). (Source: this study)

    Double

    LR2
    R-squared of Linear Regression (Source: this study)

    Double

    LSE
    Standard Error of Linear Regression (Source: this study)

    Double

    LCI90
    Confidence Interval of Linear Regression (Source: this study)

    Double

    SCAMMONBAY_Relationship_Class
    Relates values in the community table to the Statistics_Table using Location_ID (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    SCAMMONBAY_Shoreline_Envelope
    The shoreline envelope feature class was created using the positional outputs of the DSAS analysis. The shoreline envelope is a line between the shoreline position furthest from land and most landward, which shows the range of shoreline position locations at one transect. Shoreline envelopes show how much change has occurred at each transect between the time periods analyzed. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    Azimuth
    Used to record the azimuth of the transect measured in degrees clockwise from north. (Source: this study)

    Double

    Group_
    Identifier for which group the transect is in based on Baseline ID. Values in this field assigned by DSAS are based on input by user for grouping transects. (Source: this study)

    Integer

    BaselineID
    Identifier for which baseline segment the transect was cast from. (Source: this study)

    Integer

    TransOrder
    Transect order, from 1 to x number of transects. Assigned by DSAS on the basis of transect order along the baseline or baselines. This field provides the user with a method to sort transect data from the start of the baseline segment with an ID=1 and increment sequentially to the end of the final baseline segment (Himmelstoss, 2009). (Source: this study)

    Integer

    Proctime
    Time and date of when each transect was cast. (Source: this study)

    String

    StartX
    Assigned by DSAS automatically to record the X coordinate of the beginning of the transect. (Source: this study)

    Double

    StartY
    Assigned by DSAS automatically to record the Y coordinate of the beginning of the transect. (Source: this study)

    Double

    EndX
    Assigned by DSAS automatically to record the X coordinate of the end of the transect. (Source: this study)

    Double

    EndY
    Assigned by DSAS automatically to record the Y coordinate of the end of the transect. (Source: this study)

    Double

    SCAMMONBAY_Shorelines
    Shoreline positions are a representation of a linear shoreline feature at a given point in time. These data were visually interpreted from historical and current orthorectified aerial photographs and delineated in ArcGIS. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    Date_
    Acquisition date of the imagery used to delineate shoreline position. (Source: this study)

    String

    Uncertainty
    Sum of squares of four uncertainty values associated with a shoreline position, including positional uncertainty associated with ground control points, horizontal uncertainty associated with orthorectification of the aerial imagery, spatial uncertainty associated with the spatial resolution of the imagery, and uncertainty due to shoreline indicator interpretation during the digitization process (Gould and others, 2015). (Source: this study)

    Double

    Digitizer
    Name of the digitizer who delineated the shoreline. (Source: this study)

    SString

    Agency
    Name of the agency that delineated the shoreline. (Source: this study)

    String

    SIndicator
    Shoreline indicator used to delineate shoreline position (e.g. visible wet/dry line or vegetation line; Gould and others, 2015). (Source: this study)

    String

    Release_Date
    Date the shoreline was released/published by the originating agency (Source: this study)

    Double

    Source
    Source agency or organization of the imagery used to delineate shoreline position. (Source: this study)

    String

    SCAMMONBAY_Statistics_Table
    Shoreline statistics at the transects are variable along the coast. In order to evaluate shoreline change for alongshore segments surrounding community locations, these alongshore shoreline statistics have been quantified using further statistics. The community statistics table shows the mean, standard deviation, etc. of a group of transects for particular alongshore location (as defined by the community feature class). (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    Community_Name
    Name of community. (Source: this study)

    Double

    Profile_Location
    Specific name of the community site location (if more than one site per community). (Source: this study)

    Double

    Statistics_Description
    Type of statistic (mean, standard deviation, etc.) for each of the shoreline change statistics (End Point Rate, Net Shoreline Movement, etc.) (Source: this study)

    Double

    EPR
    The end point rate is calculated by dividing the distance of shoreline movement by the time elapsed between the oldest and the most recent shoreline (Himmelstoss, 2009). (Source: this study)

    Double

    ECI
    Confidence Interval of Endpoint Rate (Source: this study)

    Double

    SCE
    The shoreline change envelope reports a distance, not a rate. The SCE is the distance between the shoreline farthest from and closest to the baseline at each transect in meters. This represents the total change in shoreline movement for all available shoreline positions and is not related to their dates (Himmelstoss, 2009). (Source: this study)

    Double

    NSM
    The net shoreline movement reports a distance, not a rate. The NSM is associated with the dates of only two shorelines. It reports the distance between the oldest and youngest shorelines for each transect in meters (Himmelstoss, 2009). (Source: this study)

    Double

    LMS
    In ordinary and weighted least-squares regression, the best-fit line is placed through the points in such a way as to minimize the sum of the squared residuals. In the linear regression method, the sample data are used to calculate a mean offset, and the equation for the line is determined by minimizing this value so that the input points are positioned as close to the regression line as possible. In the least median of squares method the median value of the squared residuals is used instead of the mean to determine the best-fit equation for the line. This method is a more robust regression estimator that minimizes the influence of an anomalous outlier on the overall regression equation. The Least Median of Squares rate is the slope of this best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WLR
    In a weighted linear regression, more reliable data are given greater emphasis or weight towards determining a best-fit line. In the computation of rate-of-change statistics for shorelines, greater emphasis is placed on data points for which the position uncertainty is smaller. The Weighted Linear Regression Rate is the slope of that best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WR2
    R-squared of Weighted Linear Regression (Source: this study)

    Double

    WSE
    Standard Error of Linear Regression (Source: this study)

    Double

    WCI90
    Confidence Interval of Weighted Linear Regression (Source: this study)

    Double

    LRR
    A linear regression rate-of-change statistic can be determined by fitting a least-squares regression line to all shoreline points for a particular transect. The regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The Linear Regression Rate is the slope of that line (Himmelstoss, 2009). (Source: this study)

    Double

    LR2
    R-squared of Linear Regression (Source: this study)

    Double

    LSE
    Standard Error of Linear Regression (Source: this study)

    Double

    LCI90
    Confidence Interval of Linear Regression (Source: this study)

    Double

    Location_ID
    Unique numbered identifier for each community site. (Source: this study)

    Double

    SCAMMONBAY_Transects
    Transects that are automatically generated by DSAS at a 90 degree angle to the user-specified baseline. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    Azimuth
    Used to record the azimuth of the transect measured in degrees clockwise from north. (Source: this study)

    Double

    Group_
    Identifier for which group the transect is in based on Baseline ID. Values in this field assigned by DSAS are based on input by user for grouping transects. (Source: this study)

    Integer

    TransectId
    Unique identifier for transect intersecting with the shorelines. (Source: this study)

    Integer

    BaselineID
    Identifier for which baseline segment the transect was cast from. (Source: this study)

    Integer

    TransOrder
    Transect order, from 1 to x number of transects. Assigned by DSAS on the basis of transect order along the baseline or baselines. This field provides the user with a method to sort transect data from the start of the baseline segment with an ID=1 and increment sequentially to the end of the final baseline segment (Himmelstoss, 2009). (Source: this study)

    Integer

    Proctime
    Time and date of when each transect was cast. (Source: this study)

    String

    StartX
    Assigned by DSAS automatically to record the X coordinate of the beginning of the transect. (Source: this study)

    Double

    StartY
    Assigned by DSAS automatically to record the Y coordinate of the beginning of the transect. (Source: this study)

    Double

    EndX
    Assigned by DSAS automatically to record the X coordinate of the end of the transect. (Source: this study)

    Double

    EndY
    Assigned by DSAS automatically to record the Y coordinate of the end of the transect. (Source: this study)

    Double

    TCD
    Total cumulative distance of shoreline alongshore in meters. (Source: this study)

    Double

    EPR
    The end point rate is calculated by dividing the distance of shoreline movement by the time elapsed between the oldest and the most recent shoreline (Himmelstoss, 2009). (Source: this study)

    Double

    ECI
    Confidence Interval of Endpoint Rate (Source: this study)

    Double

    SCE
    The shoreline change envelope reports a distance, not a rate. The SCE is the distance between the shoreline farthest from and closest to the baseline at each transect in meters. This represents the total change in shoreline movement for all available shoreline positions and is not related to their dates (Himmelstoss, 2009). (Source: this study)

    Double

    NSM
    The net shoreline movement reports a distance, not a rate. The NSM is associated with the dates of only two shorelines. It reports the distance between the oldest and youngest shorelines for each transect in meters (Himmelstoss, 2009). (Source: this study)

    Double

    LMS
    In ordinary and weighted least-squares regression, the best-fit line is placed through the points in such a way as to minimize the sum of the squared residuals. In the linear regression method, the sample data are used to calculate a mean offset, and the equation for the line is determined by minimizing this value so that the input points are positioned as close to the regression line as possible. In the least median of squares method the median value of the squared residuals is used instead of the mean to determine the best-fit equation for the line. This method is a more robust regression estimator that minimizes the influence of an anomalous outlier on the overall regression equation. The Least Median of Squares rate is the slope of this best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WLR
    In a weighted linear regression, more reliable data are given greater emphasis or weight towards determining a best-fit line. In the computation of rate-of-change statistics for shorelines, greater emphasis is placed on data points for which the position uncertainty is smaller. The Weighted Linear Regression Rate is the slope of that best-fit line (Himmelstoss, 2009). (Source: this study)

    Double

    WR2
    R-squared of Weighted Linear Regression (Source: this study)

    Double

    WSE
    Standard Error of Linear Regression (Source: this study)

    Double

    WCI90
    Confidence Interval of Weighted Linear Regression (Source: this study)

    Double

    LRR
    A linear regression rate-of-change statistic can be determined by fitting a least-squares regression line to all shoreline points for a particular transect. The regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The Linear Regression Rate is the slope of that line (Himmelstoss, 2009). (Source: this study)

    Double

    LR2
    R-squared of Linear Regression (Source: this study)

    Double

    LSE
    Standard Error of Linear Regression (Source: this study)

    Double

    LCI90
    Confidence Interval of Linear Regression (Source: this study)

    Double


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    These materials were prepared in partnership with the Federal Emergency Management Agency through a Cooperative Technical Partner grant. Data were produced by the Alaska Division of Geological & Geophysical Surveys, the U.S. Geological Survey, and the National Park Service.

  3. To whom should users address questions about the data?

    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Coastal Hazards Program
    3651 Penland Pkwy
    Anchorage, AK 99508
    USA

    907-451-5026 (voice)
    dggspubs@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays


Why was the data set created?

Coastlines are dynamic features that change shape and position on a range of timescales. These changes can result in erosion or aggradation of the coastline fronting valued systems (e.g. community infrastructure). This geodatabase for the community of Scammon Bay includes shoreline positions, shoreline envelopes, and community location identifiers, as well as geodatabase tables of shoreline change statistics, shoreline change analysis transect information, and summary shoreline change statistics.


How was the data set created?

  1. From what previous works were the data drawn?

    Gould and others, 2015 (source 1 of 3)
    Gould, A.I., Kinsman, N.E.M., and Hendricks, M.D., 2015, Guide to projected shoreline positions in the Alaska shoreline change tool: Miscellaneous Publication MP 158, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 11 p
    Type_of_Source_Media: paper
    Source_Contribution: Projected shoreline positions

    Himmelstoss, 2009 (source 2 of 3)
    Himmelstoss, E.A., 2009, DSAS 4.0 Installation Instructions and User Guide in: Thieler, E.R., Himmelstoss, E.A., Zichichi, J.L., and Ergul, Ayhan. 2009 Digital Shoreline Analysis System (DSAS) version 4.0 - An ArcGIS extension for calculating shoreline change: U.S. Geological Survey Open-File Report OFR 2008-1278, U.S. Geological Survey, United States.

    Type_of_Source_Media: paper
    Source_Contribution: Projected shoreline positions

    Thieler, E.E. and others, 2008 (source 3 of 3)
    Thieler, E.E., Himmelstoss, E.A., Zichichi, J.L., and Ergul, Ayhan, 2008, The digital shoreline analysis system (DSAS) version 4.0 - An ArcGIS extension for calculating shoreline change: Open-File Report OF 2008-1278, U.S. Geological Survey, United States.

    Online Links:

    Type_of_Source_Media: ArcGIS extension
    Source_Contribution: Projected shoreline positions

  2. How were the data generated, processed, and modified?

    Date: 2017 (process 1 of 3)
    Historical shoreline compilation - Using orthorectified historically and recently collected aerial imagery, we delineated past shoreline positions fronting Alaska communities. The agency or organization that produced the imagery used to delineate shoreline position is noted in the Shoreline Positions data table.

    Date: 2017 (process 2 of 3)
    Rates of shoreline change - We computed rates of shoreline change along cross shore transects cast approximately every 50 meters along the delineated shorelines using the Digital Shoreline Analysis System

    Date: 2017 (process 3 of 3)
    Summary results - We summarized the results for each community by computing summary statistics of the resulting shoreline change statistics at community-located profiles.

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    DGGS staff have performed visual qualitative assessment of each shoreline file to ensure consistency between the digitized lines and originating images. Several factors have potential to introduce uncertainty in the measured or interpreted results. The factors include: positional uncertainty associated with ground control points, horizontal uncertainty associated with orthorectification of the aerial imagery, spatial uncertainty associated with the spatial resolution of the imagery, and uncertainty due to shoreline indicator interpretation during the digitization process. The accompanying delivery report provides additional information about the procedures used to determine values for shoreline positions, shoreline envelopes, and community location identifiers, shoreline change statistics, shoreline change analysis transect information, and summary shoreline change statistics.

  2. How accurate are the geographic locations?

    Shoreline positions are a representation of a linear shoreline feature at a given point in time. These data were visually interpreted from historical and current orthorectified aerial photographs and delineated in ArcGIS. These accuracies are dependent on a number of variables. The details of their calculation are explained in the associated publications: Gould, A.I., Kinsman, N.E.M., and Hendricks, M.D., 2015, Guide to projected shoreline positions in the Alaska shoreline change tool: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 158, 11 p. doi:10.14509/29503

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Gaps in shoreline data may occur where a shoreline indicator is not identifiable (example: poorly defined shoreline indicator, cloud cover in imagery, etc.) or does not exist (example: tidal inlet, revetment or other coastal structure).

  5. How consistent are the relationships among the observations, including topology?

    not applicable


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

  1. Who distributes the data set? (Distributor 1 of 1)

    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Coastal Hazards Program
    3651 Penland Pkwy
    Anchorage, AK 99508
    USA

    907-451-5026 (voice)
    dggspubs@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity, whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requestor or anyone else exceed the fee paid for the electronic service or product.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 04-May-2018
Metadata author:
Simone Montayne
3354 College Road
Fairbanks, AK 99709-3707
USA

907-451-5020 (voice)

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.21 on Fri Jun 22 14:07:25 2018