Metadata: Identification_Information: Citation: Citation_Information: Originator: University of Hawaii Coastal Geology Group Publication_Date: 2011 Title: KauaiS_LT - Digital Shoreline Analysis System (DSAS) version 4.2 transects with long-term weighted linear regression rate calculations for the Kauai south region from Waimea to Kipu Kai, Hawaii Geospatial_Data_Presentation_Form: vector digital data Series_Information: Series_Name: Open-File Report Issue_Identification: 2011-1009 Publication_Information: Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA Publisher: U.S. Geological Survey, Coastal and Marine Geology Program Online_Linkage: https://doi.org/10.3133/ofr20111009 Online_Linkage: https://pubs.usgs.gov/of/2011/1009/data.html Online_Linkage: https://pubs.usgs.gov/of/2011/1009/ Larger_Work_Citation: Citation_Information: Originator: Bradley M. Romine Originator: Charles H. Fletcher Originator: Ayesha S. Genz Originator: Matthew M. Barbee Originator: Matthew Dyer Originator: Tiffany R. Anderson Originator: S. Chyn Lim Originator: Sean Vitousek Originator: Christopher Bochicchio Originator: Bruce Richmond Publication_Date: 2011 Title: National Assessment of Shoreline Change: A GIS Compilation of Vector Shorelines and Associated Change Data for the Sandy Shorelines of Kauai, Oahu, and Maui; Hawaii Series_Information: Series_Name: Open-File Report Issue_Identification: 2011-1009 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: https://pubs.usgs.gov/of/2011/1009/ Description: Abstract: Sandy ocean beaches are a popular recreational destination, often surrounded by communities containing valuable real estate. Development is on the rise despite the fact that coastal infrastructure is subjected to flooding and erosion. As a result, there is an increased demand for accurate information regarding past and present shoreline changes. To meet these national needs, the Coastal and Marine Geology Program of the U.S. Geological Survey (USGS) is compiling existing reliable historical shoreline data along open-ocean sandy shores of the conterminous United States and parts of Alaska and Hawaii under the National Assessment of Shoreline Change project. There is no widely accepted standard for analyzing shoreline change. Existing shoreline data measurements and rate calculation methods vary from study to study and prevent combining results into state-wide or regional assessments. The impetus behind the National Assessment project was to develop a standardized method of measuring changes in shoreline position that is consistent from coast to coast. The goal was to facilitate the process of periodically and systematically updating the results in an internally consistent manner. Purpose: This dataset consists of long-term (1926-2008) shoreline change rates for the Kauai South region from Waimea to Kipu Kai. Rate calculations were computed within a GIS using the Digital Shoreline Analysis System (DSAS) version 4.2, an ArcGIS extension developed by the U.S. Geological Survey. Long-term rates of shoreline change were calculated using a weighted linear regression rate based on all available shoreline data. A reference baseline was used as the originating point for the orthogonal transects imported into the DSAS software. The transects intersect each shoreline establishing measurement points, which are then used to calculate long-term rates. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2011 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -159.690454 East_Bounding_Coordinate: -159.375421 North_Bounding_Coordinate: 21.959396 South_Bounding_Coordinate: 21.872315 Keywords: Theme: Theme_Keyword_Thesaurus: USGS Metadata Identifier Theme_Keyword: USGS:3f900c30-825a-45a8-956c-902091ff6377 Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: Shoreline Theme_Keyword: Historic Shoreline Theme_Keyword: Shoreline Change Rate Theme_Keyword: Erosion Theme_Keyword: Accretion Theme_Keyword: Weighted Linear Regression Rate Theme_Keyword: Baseline Theme_Keyword: Transect Theme_Keyword: Digital Shoreline Analysis System Theme_Keyword: DSAS Theme_Keyword: U.S. Geological Survey Theme_Keyword: USGS Theme_Keyword: Coastal and Marine Geology Program Theme_Keyword: CMGP Theme_Keyword: Woods Hole Coastal and Marine Science Center Theme_Keyword: WHCMSC Theme_Keyword: National Assessment of Shoreline Change Project Theme_Keyword: University of Hawaii Coastal Geology Group Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: oceans Theme_Keyword: environment Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Marine Realms Information Bank (MRIB) Keywords Theme_Keyword: effects of coastal change Theme_Keyword: coastal processes Theme_Keyword: shoreline accretion Theme_Keyword: shoreline erosion Theme: Theme_Keyword_Thesaurus: USGS Thesaurus Theme_Keyword: coastal processes Theme_Keyword: erosion Theme_Keyword: shoreline accretion Theme: Theme_Keyword_Thesaurus: Coastal and Marine Ecological Classification Standard (CMECS) Theme_Keyword: Continental/Island Shore Complex Place: Place_Keyword_Thesaurus: None Place_Keyword: United States Place_Keyword: Hawaii Place_Keyword: Kauai Place_Keyword: South Kauai Place_Keyword: Waimea, Hawaii Place_Keyword: Kipu Kai, Hawaii Place: Place_Keyword_Thesaurus: Coastal and Marine Ecological Classification Standard (CMECS) Place_Keyword: Hawaii Ecoregion Stratum: Stratum_Keyword_Thesaurus: Coastal and Marine Ecological Classification Standard (CMECS) Stratum_Keyword: Substrate Access_Constraints: none Use_Constraints: Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the University of Hawaii Coastal Geology Group as the originator of the dataset. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: University of Hawaii Coastal Geology Group Contact_Person: Dr. Charles H. Fletcher Contact_Position: professor Contact_Address: Address_Type: mailing and physical address Address: University of Hawaii Coastal Geology Group Address: 1680 East-West Road Address: POST Room 721 City: Honolulu State_or_Province: HI Postal_Code: 96822 Country: USA Contact_Voice_Telephone: 808-956-9513 Contact_Facsimile_Telephone: 808-956-5512 Contact_Electronic_Mail_Address: fletcher@soest.hawaii.edu Native_Data_Set_Environment: Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.0.1770 Cross_Reference: Citation_Information: Originator: E.R. Thieler Originator: E.A. Himmelstoss Originator: J.L. Zichichi Originator: A. Ergul Publication_Date: 2009 Title: Digital Shoreline Analysis System (DSAS) version 4.0: an ArcGIS extension for calculating shoreline change Series_Information: Series_Name: Open-File Report Issue_Identification: 2008-1278 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Other_Citation_Details: Current version is 4.2. Online_Linkage: https://pubs.er.usgs.gov/publication/ofr20081278 Online_Linkage: https://woodshole.er.usgs.gov/project-pages/DSAS/ Cross_Reference: Citation_Information: Originator: Charles H. Fletcher Originator: Bradley M. Romine Originator: Ayesha S. Genz Originator: Matthew M. Barbee Originator: Matthew Dyer Originator: Tiffany R. Anderson Originator: S. Chyn Lim Originator: Sean Vitousek Originator: Christopher Bochicchio Originator: Bruce Richmond Publication_Date: 2011 Title: National Assessment of Shoreline Change: Historical Shoreline Change in the Hawaiian Islands Series_Information: Series_Name: Open-File Report Issue_Identification: 2011-1051 Publication_Information: Publication_Place: Resotn, VA Publisher: U.S. Geological Survey Online_Linkage: https://pubs.usgs.gov/of/2011/1051/ Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: The attributes in this layer are based on the field requirements of the Digital Shoreline Analysis System (DSAS) software (USGS Open-File Report 2008-1278). Transects were constructed manually outside of DSAS and imported into DSAS for calculation of shoreline change rates by the software. The data have been quality checked for intended location and shoreline intersection. Logical_Consistency_Report: These data were constructed outside of DSAS and imported to DSAS v4.2, an automated software program which does not perform checks for fidelity of the input features. The transects were visually inspected and sometimes manually adjusted within a standard ArcMap edit session to adjust the position at which an individual transect intersected the shorelines. Completeness_Report: This dataset contains the transects imported to the DSAS software application that were used to calculate long-term shoreline change rates for the region. Lineage: Process_Step: Process_Description: Transect features were generated outside of DSAS and imported to DSAS v4.2 in ArcMap v9.3 for calculation of long-term shoreline change rates for the region. Transects are roughly perpendicular to the historical shorelines and spaced roughly 20 meters along the shore. Please see the DSAS help file distributed with the DSAS software, or visit the USGS website at: https://pubs.er.usgs.gov/publication/ofr20081278. This process step and all subsequent process steps were performed by the same person: Bradley Romine Process_Date: 20090220 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Bradley M. Romine Contact_Organization: University of Hawaii Coastal Geology Group Contact_Position: graduate student, research assistant Contact_Address: Address_Type: mailing and physical address Address: University of Hawaii Coastal Geology Group Address: 1680 East-West Road Address: POST Room 721 City: Honolulu State_or_Province: HI Postal_Code: 96822 Country: USA Contact_Voice_Telephone: 808-956-3605 Contact_Facsimile_Telephone: 808-956-5512 Contact_Electronic_Mail_Address: romine@hawaii.edu Process_Step: Process_Description: Rate Calculations Performed in DSAS v4.2 using ArcMap v9.3. Parameters Used: shoreline layer=KauaiS_shorelines, shoreline date field=DATE_, shoreline uncertainty field name=ACCURACY, the default accuracy=0 (accuracy values provided for all shorelines), shoreline intersection parameters=closest intersection, stats calculations=[weighted linear regression (WLR)], shoreline threshold=3, confidence interval=95%, Output rate table name=EKauai_transects_LT_rates_20101028_155408. Process_Date: 20101028 Process_Step: Process_Description: Shoreline rates table (SKauai_transects_LT_rates_20101028_155408.dbf) was joined to the transect feature class in ArcCatalog v9.3 with ArcToolbox > Data Management Tools > Joins > Join Field. Parameters: input join field - OBJECTID; output join field - TransID; join table - SKauai_transects_LT_rates_20101028_155408; based on field in table: TransectID; join attributes: WLR, WCI95. This method permanently adds the selected attributes to the transect feature class. Process_Date: 20111017 Process_Step: Process_Description: The joined transect feature class was exported to a shapefile in ArcMap v9.3 by right-clicking the transect layer > data > export data. Process_Date: 20111017 Process_Step: Process_Description: The exported transect shapefile was projected in ESRI's ArcToolbox (v.9.3) > Data Management Tools > Projections and Transformations > Feature > Project. Parameters: input projection - UTM zone 4N (NAD 83); output projection - geographic coordinates (WGS84); transformation - NAD_1983_To_WGS_1984_3 (Hawaii). Process_Date: 20111017 Process_Step: Process_Description: Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Process_Date: 20170823 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Alan O. Allwardt Contact_Position: Contractor -- Information Specialist Contact_Address: Address_Type: mailing and physical address Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Contact_Voice_Telephone: 831-460-7551 Contact_Facsimile_Telephone: 831-427-4748 Contact_Electronic_Mail_Address: aallwardt@usgs.gov Process_Step: Process_Description: Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata. Process_Date: 20180426 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Alan O. Allwardt Contact_Position: Contractor -- Information Specialist Contact_Address: Address_Type: mailing and physical address Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Contact_Voice_Telephone: 831-460-7551 Contact_Facsimile_Telephone: 831-427-4748 Contact_Electronic_Mail_Address: aallwardt@usgs.gov Process_Step: Process_Description: Edits to the metadata were made to fix any errors that MP v 2.9.46 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Added a data landing page link as the first link in the identification section. Removed LIDAR bounding coordinates - an artifact of Esri and MP processing. Minor fixes to the attribute format for some attributes were needed. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. Added additional information to a cross-reference and fixed the online link. Attempted to modify http to https where appropriate. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. Process_Date: 20180515 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: VeeAnn A. Cross Contact_Position: Marine Geologist Contact_Address: Address_Type: Mailing and Physical Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: 508-548-8700 x2251 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: vatnipp@usgs.gov Process_Step: Process_Description: Crossref DOI link was added as the first link in the metadata. Process_Date: 20191118 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: VeeAnn A. Cross Contact_Position: Marine Geologist Contact_Address: Address_Type: Mailing and Physical Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: 508-548-8700 x2251 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: vatnipp@usgs.gov Process_Step: Process_Description: Added keywords section with USGS persistent identifier as theme keyword. Process_Date: 20200908 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: VeeAnn A. Cross Contact_Position: Marine Geologist Contact_Address: Address_Type: Mailing and Physical Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: 508-548-8700 x2251 Contact_Facsimile_Telephone: 508-457-2310 Contact_Electronic_Mail_Address: vatnipp@usgs.gov Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: String Point_and_Vector_Object_Count: 790 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geographic: Latitude_Resolution: 0.000001 Longitude_Resolution: 0.000001 Geographic_Coordinate_Units: Decimal degrees Geodetic_Model: Horizontal_Datum_Name: D_WGS_1984 Ellipsoid_Name: WGS_1984 Semi-major_Axis: 6378137.000000 Denominator_of_Flattening_Ratio: 298.257224 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: KauaiS_LT Entity_Type_Definition: Transects are generated outside of DSAS at a 90 degree angle to the user-specified baseline and imported to DSAS. Entity_Type_Definition_Source: U.S. Geological Survey 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: OBJECTID Attribute_Definition: The object identification field establishes a unique ID for each row in the attribute table. This number is used by DSAS to relate all shoreline-change results tables with the transects. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Information unavailable from original metadata. Attribute: Attribute_Label: BaselineID Attribute_Definition: Unique identification number of the baseline segment. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0 Range_Domain_Maximum: unlimited Attribute: Attribute_Label: Group Attribute_Definition: Values in this field are based on input by user for grouping transects (=0, if no grouping). Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Information unavailable from original metadata. Attribute: Attribute_Label: TransOrder Attribute_Definition: Ordering of transects along the baseline. Used to allow user to sort transect data along the baseline from baseline start to baseline end. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0 Range_Domain_Maximum: unlimited Attribute: Attribute_Label: StartX Attribute_Definition: X coordinate of the beginning of the transect in meter units (UTM zone 4N, NAD 83). Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Values based on data set extent. Attribute: Attribute_Label: StartY Attribute_Definition: Y coordinate of the beginning of the transect in meter units (UTM zone 4N, NAD 83). Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Values based on data set extent. Attribute: Attribute_Label: EndX Attribute_Definition: X coordinate of the end of the transect in meter units (UTM zone 4N, NAD 83). Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Values based on data set extent. Attribute: Attribute_Label: EndY Attribute_Definition: Y coordinate of the end of the transect in meter units (UTM zone 4N, NAD 83). Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Values based on data set extent. Attribute: Attribute_Label: Azimuth Attribute_Definition: Azimuth of the transect measure in degrees clockwise from North. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Values based on data set extent. Attribute: Attribute_Label: SHAPE_Leng Attribute_Definition: Length of feature in meter units (UTM zone 4N, NAD 83). Attribute_Definition_Source: ESRI Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 150.000000 Range_Domain_Maximum: 200.000004 Attribute: Attribute_Label: WLR Attribute_Definition: Long-term weighted least squares (WLR) shoreline change rate in meters per year. A negative value indicates beach erosion (shoreline recession) and a positive value indicates beach accretion (shoreline progradation). In a weighted linear regression, more reliable data are given greater emphasis or weight towards determining a best-fit line. The uncertainty field ("accuracy") of the shoreline feature class is used to calculate the weight. The weight is equal to the inverse of the shoreline uncertainty squared. Therefore, when fitting a trend line, greater emphasis is placed on data points for which the positional uncertainty is smaller. Rates were calculated only at transects with 3 or more historical shoreline intersects (shoreline threshold=3). Transects with less than 3 shoreline intersects were given a 'null' value of -9999. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Transects with less than 3 shoreline intersects were given a WLR 'null' value of -9999. Attribute: Attribute_Label: WCI95 Attribute_Definition: 95% confidence interval of WLR shoreline change rate in meters per year. The standard error of the slope with confidence interval describes the uncertainty of the reported rate. The confidence interval is calculated by multiplying the standard error of the slope of the WLR (meters/year) by the two-tailed test statistic at the specified confidence percentage (95). For example, if the reported WLR is 1.34 m/year and the 95 percent confidence interval (WCI95) is 0.5 then you can be 95 percent confident that the true rate of change is 1.34 m +- 0.5 meters/year. Rates and uncertainties were calculated only at transects with 3 or more historical shoreline intersects (shoreline threshold=3). Transects with less than 3 shoreline intersects were given a 'null' value of -9999. Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Unrepresentable_Domain: Transects with less than 3 shoreline intersects were given a WCI95 'null' value of -9999. Overview_Description: Entity_and_Attribute_Overview: All calculations for length are in meter units and were based on the UTM zone 4N NAD83 projection. Entity_and_Attribute_Detail_Citation: U.S. Geological Survey Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Country: USA Contact_Voice_Telephone: 508-548-8700 Contact_Facsimile_Telephone: 508-457-2310 Resource_Description: Downloadable data. Distribution_Liability: Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. 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: Format_Name: Shapefile Format_Version_Number: ArcGIS 9.3 Format_Specification: ESRI polyline shapefile Format_Information_Content: This WinZip file contains a shapefile of transects generated by the Digital Shoreline Analysis System including long-term rate calculations for the Kauai South region from Waimea to Kipu Kai. File_Decompression_Technique: Use WinZip or pkUnzip Transfer_Size: 0.5 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: https://pubs.usgs.gov/of/2011/1009/data/Kauai/KauaiS/KauaiS_LT.zip Access_Instructions: Data may be downloaded via the World Wide Web (WWW). Fees: None Technical_Prerequisites: This zip file contains data available in Environmental Systems Research Institute (ESRI) polyline shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing the data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com. Metadata_Reference_Information: Metadata_Date: 20240318 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Bradley M. Romine Contact_Organization: University of Hawaii Coastal Geology Contact_Position: graduate student, research assistant Contact_Address: Address_Type: mailing and physical address Address: University of Hawaii Coastal Geology Group Address: 1680 East-West Road Address: POST Room 721 City: Honolulu State_or_Province: HI Postal_Code: 96822 Country: USA Contact_Voice_Telephone: 808-956-3605 Contact_Facsimile_Telephone: 808-956-5512 Contact_Electronic_Mail_Address: whsc_data_contact@usgs.gov Contact_Instructions: The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240318) Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time