Coastal Features Extracted from Landsat Collection 2 Data, Northern Chandeleur Islands, Louisiana

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Bernier, Julie C., and Williams, Breanna N., 20251219, Coastal Features Extracted from Landsat Collection 2 Data, Northern Chandeleur Islands, Louisiana:.

   This is part of the following larger work.
   Bernier, Julie C., Williams, Breanna N., and Miselis, Jennifer L., 20210921, Coastal Land-Cover and Feature Datasets Derived from Landsat Satellite Imagery, Northern Chandeleur Islands, Louisiana: U.S. Geological Survey data release doi:10.5066/P9HY3HOR, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P9HY3HOR

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -88.932712
   East_Bounding_Coordinate: -88.742256
   North_Bounding_Coordinate: 30.097824
   South_Bounding_Coordinate: 29.720211
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 22-Dec-2017

   Currentness_Reference:

   ground condition

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

   Geospatial_Data_Presentation_Form: raster and tabular 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: 16
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.0
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 30
      Ordinates (y-coordinates) are specified to the nearest 30
      Planar coordinates are specified in Meters
      The horizontal datum used is D WGS 1984.
      The ellipsoid used is WGS 1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      
7. How does the data set describe geographic features?

   nchan_coll2_shrln_20171222_20241115.shp, nchan_coll2_sandext_20171222_20241115.shp, nchan_coll2_vegext_20171222_20241115.shp

   Vector shoreline, sand, and vegetated feature extents in Esri shapefile (.shp) format, contained in nchan_coll2_features.zip. (Source: USGS)

   FID

   Internal feature number (Source: Esri) Sequential unique whole numbers that are automatically generated.

   Shape

   Feature geometry (Source: Esri) Coordinates defining the features.

   IMG_DATE

   Image acquisition date (Source: USGS) Source image acquisition date written as DD-MON-YYYY (2-digit day, 3-letter month, 4-digit year).

   DEC_YEAR

   Source image-acquisition date, in decimal years. (Source: USGS)

   Range of values
   Minimum:	2017.975
   Maximum:	2024.873
   Units:	Decimal year
   Resolution:	0.001

   nchan_perp_transects_300m.shp

   Cross-shore transect locations in Esri shapefile (.shp) format, contained in nchan_coll2_features.zip. (Source: USGS)

   FID

   Internal feature number (Source: Esri) Sequential unique whole numbers that are automatically generated.

   Shape

   Feature geometry (Source: Esri) Coordinates defining the features.

   Transect

   Transect number (Source: USGS)

   Range of values
   Minimum:	1
   Maximum:	132
   Units:	Dimensionless
   Resolution:	1

   StartX

   UTM coordinates of transect starting x position. (Source: USGS)

   Range of values
   Minimum:	319282.942095
   Maximum:	325039.250404
   Units:	Meters
   Resolution:	0.000001

   StartY

   UTM coordinates of transect starting y position. (Source: USGS)

   Range of values
   Minimum:	3289009.250058
   Maximum:	3326250.763767
   Units:	Meters
   Resolution:	0.000001

   Azimuth

   Azimuth of transect cast (Source: USGS)

   Range of values
   Minimum:	48.408288
   Maximum:	117.397400
   Units:	Meters
   Resolution:	0.000001

   nchan_coll2_featmetrics_2017_2024.csv

   Comma-separated values (.csv) file detailing derived feature metrics for each image-acquisition date, contained in nchan_coll2_features.zip. (Source: USGS)

   Transect

   Transect number (Source: USGS)

   Range of values
   Minimum:	1
   Maximum:	132
   Units:	Dimensionless
   Resolution:	1

   IMG_DATE

   Image acquisition date (Source: USGS) Source image acquisition date written as DD-MON-YYYY (2-digit day, 3-letter month, 4-digit year).

   DEC_YEAR

   Source image-acquisition date, in decimal years. (Source: USGS)

   Range of values
   Minimum:	2017.975
   Maximum:	2024.873
   Units:	Decimal year
   Resolution:	0.001

   SHRLN_min

   Distance, in meters, along transect from baseline to first intersection with shoreline vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	564.520
   Maximum:	5072.489
   Units:	Meters
   Resolution:	0.001

   SAND_min

   Distance, in meters, along transect from baseline to first intersection with sand extent vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	598.141
   Maximum:	4957.164
   Units:	Meters
   Resolution:	0.0010

   SAND_max

   Distance, in meters, along transect from baseline to last intersection with sand extent vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	689.084
   Maximum:	5012.648
   Units:	Meters
   Resolution:	0.001

   VEG_min

   Distance, in meters, along transect from baseline to first intersection with vegetated extent vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	695.207
   Maximum:	4279.561
   Units:	Meters
   Resolution:	0.001

   VEG_max

   Distance, in meters, along transect from baseline to last intersection with vegetated extent vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	940.156
   Maximum:	4327.063
   Units:	Meters
   Resolution:	0.001

   SHRLN_max

   Distance, in meters, along transect from baseline to last intersection with shoreline vector. (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	790.196
   Maximum:	5336.275
   Units:	Meters
   Resolution:	0.001

   ISLP

   Width, in meters, of barrier-island platform (sea shoreline to back-barrier shoreline). (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	17.614
   Maximum:	1461.495
   Units:	Meters
   Resolution:	0.001

   BEACH

   Width, in meters, of barrier-island beach (maximum sand extent to seaward shoreline). (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	21.429
   Maximum:	431.331
   Units:	Meters
   Resolution:	0.001

   VEG

   Width, in meters, of barrier-island vegetation (vegetated extent). (Source: USGS)

   Value	Definition
   NoData	Feature is not present along the transect.
   Excl	Feature was excluded from dataset (see process step description for additional details).

   Range of values
   Minimum:	20.308
   Maximum:	1217.769
   Units:	Meters
   Resolution:	0.001

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Julie C. Bernier
   • Breanna N. Williams
2. Who also contributed to the data set?
   U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, St. Petersburg Coastal and Marine Science Center (SPCMSC). Funding and (or) support for this analysis were provided as part of the Extending Government Funding and Delivering Emergency Assistance Act (Public Law 117-43), enacted on September 30, 2021. This document was improved by scientific and metadata reviews by Sydney Nick and Tess Rivenbark-Terrano (USGS SPCMSC).
3. To whom should users address questions about the data?
   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

Why was the data set created?

How was the data set created?

1. From what previous works were the data drawn?
2. How were the data generated, processed, and modified?

   Date: 2025 (process 1 of 5)

   For each image acquisition date, Landsat Collection 2 ARD top-of-atmosphere (TOA) reflectance (reflective bands) and TOA brightness temperature (BT; thermal infrared [TIR] bands) were downloaded from EarthExplorer (https://earthexplorer.usgs.gov/) and Level 2 surface reflectance-derived NDVI images were downloaded from the EROS ESPA On Demand Interface (https://espa.cr.usgs.gov/). Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

   Date: 2025 (process 2 of 5)

   All images were batch-processed using Spatial Model Editor in ERDAS IMAGINE. The TOA and BT bands were stacked to create 9-band multispectral images and clipped to the study-area extent. From these composite images, two additional spectral indices, mNDWI (Xu, 2006) and NBLI (Li and others, 2017), were calculated. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

   Date: 2025 (process 3 of 5)

   Land-cover classification was performed using progressive, automatic thresholding of spectral indices. First, Otsu's method (Otsu, 1979) for automatic histogram thresholding was applied to mNDWI images to create a binary land-water raster for each image acquisition date. Second, water area was masked from NBLI and NDVI images, and Otsu's method was applied to the masked images to create binary bare earth-"unclassed" and vegetated-"unclassed" rasters, respectively. Because thresholding was applied to masked NBLI and NDVI simultaneously, some pixels along the sand-vegetation boundary were classed as both sand and vegetated in this step. These pixels were mapped as sand using the following rule: if NBLI = sand and NDVI = vegetated, then final = sand (based on visual analysis during workflow development) (Bernier and others, 2021). Next, water, bare earth (sand), and vegetated areas were masked from mNDWI images, and Otsu's method was applied to the masked mNDWI image to separate the "submerged" and "emergent" intertidal areas. Finally, the binary land-cover images were converted to thematic rasters, merged, and single-pixel "clumps" were removed using a 3x3 majority filter to create a final land-cover raster dataset. The resulting land-cover rasters use the naming convention YYYYMMDD_LC##_nchan_islp_lcr_ce.img, where YYYYMMDD denotes the image-acquisition date (4-digit year, 2-digit month, 2-digit day) and LC## denotes Landsat 8 (LC08) or Landsat 9 (LC09) image source. All steps were batch-processed using the Image Processing toolbox in MATLAB (Otsu thresholding and binary image creation) or Spatial Model Editor in ERDAS IMAGINE (spectral index masking and generation of classed land-cover rasters). Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

   Date: 2025 (process 4 of 5)

   Vector shoreline (representing the boundary between intertidal and open-water areas), sand, and vegetated extents were extracted by contouring the mNDWI and masked NBLI and NDVI images using the calculated Otsu thresholds. The resulting shapefiles (one per image acquisition date) were merged into 3 shapefiles (one each for shoreline [shrln], sand [sandext], and vegetated [vegext] feature extents). Contouring was batch-processed using Python 3 Jupyter Notebooks in ArcGIS Pro. Vector features corresponding to a minimum mapping unit of less than 4 connected pixels were excluded from the final dataset. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

   Data sources produced in this process:

   • nchan_coll2_shrln_20171222_20241115.shp
   • nchan_coll2_sandext_20171222_20241115.shp
   • nchan_coll2_vegext_20171222_20241115.shp

   Date: 2025 (process 5 of 5)

   Barrier platform, beach, and vegetated widths were calculated from the intersection of the shoreline, sand, and vegetated vectors with transects spaced 300 m (10 pixels) apart alongshore. New Harbor Islands, isolated back-barrier islands that are less than 8 pixels in size, and back-barrier islands that are more than 8 pixels from the contiguous island extent were excluded from the feature metrics dataset. Transects are the same as used in Bernier and others (2021); feature intersections and along-transect widths were calculated in RStudio. Vegetated widths were not calculated along transects 56 and 57, where the oblique nature of the back-barrier marsh island, coupled with a change in baseline orientation, caused inconsistencies in delineating feature extents. Features less than 17 m wide along-transect are considered unresolvable based on the stated 12-m RMSE for Landsat L1TP products (sqrt(12^2 + 12^2) = 16.97) and were also excluded from the final dataset. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Julie C. Bernier

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   jbernier@usgs.gov

   Data sources produced in this process:

   • nchan_perp_transects_300m.shp
   • nchan_coll2_featmetrics_2017_2024.csv

3. What similar or related data should the user be aware of?
   Bernier, Julie C., Miselis, Jennifer L., and Plant, Nathaniel G., 20210921, Satellite-Derived Barrier Response and Recovery Following Natural and Anthropogenic Perturbations, Northern Chandeleur Islands, Louisiana: Remote Sensing 13(18), 3778; Special Issue "New Insights into Ecosystem Monitoring Using Geospatial Techniques".

   Online Links:

   • https://doi.org/10.3390/rs13183779

   Xu, Hanqiu, 2006, Modification of Normalised Difference Water Index (NDWI) to Enhance Open Water Features in Remotely Sensed Imagery: International Journal of Remote Sensing Volume 27, Issue 14.

   Online Links:

   • https://doi.org/10.1080/01431160600589179

   Other_Citation_Details: Pages 3025-3033
   

   Li, Hui, Wang, Cuizhen, Zhong, Cheng, Su, Aijun, Xiong, Chengren, Wang, Jinge, and Liu, Junqi, 20170307, Mapping Urban Bare Land Automatically from Landsat Imagery with a Simple Index: Remote Sensing 9(3), 249.

   Online Links:

   • https://doi.org/10.3390/rs9030249

   Otsu, Nobuyuki, 197901, A Threshold Selection Method from Gray-Level Histograms: IEEE Transactions on Systems, Man and Cybernetics Volume 9, Issue 1.

   Online Links:

   • https://doi.org/10.1109/TSMC.1979.4310076

   Other_Citation_Details: Pages 62-66
   

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

1. How well have the observations been checked?
   
2. How accurate are the geographic locations?
   Geodetic accuracy of Landsat data products depend on the accuracy, number, and distribution of the ground control points and the resolution of the digital elevation model (DEM) used. All ARD and Level-2 science products are derived from Landsat Level-1 Precision and Terrain (L1TP) corrected data and meet pre-defined image-to-image georegistration tolerances of <= 12-meter radial root mean square error (RMSE). The positional accuracy of the satellite-derived features was not systematically evaluated in this study; however, recent analyses of satellite-derived shoreline (SDS) positions extracted using similar methods to those presented here report offsets of 1/3 to 1/2 pixel (10 to 15 m) seaward of measured in-situ shoreline positions. Compared with methods that extract shoreline position from precise elevation measurements (for example, lidar or GPS surveys), SDS positions are not based on a vertical datum (for example, mean sea level or mean high water); instead, SDS positions may include intertidal areas.
3. How accurate are the heights or depths?
   
4. Where are the gaps in the data? What is missing?
   63 Landsat OLI images (Worldwide Reference System 2 [WRS-2] path 21 row 39) acquired between December 2022 and November 2024 were identified that were cloud free in the study area. To minimize the effects of water-level variations on land-cover classification, only images that were collected within 2 hours of predicted low tide or were collected on a rising tide with predicted water levels at time of acquisition less than mean sea level (National Ocean Service [NOS] Center for Operational Oceanographic Products and Services [CO-OPS] station 8760172, Chandeleur Light, LA) were analyzed. The resulting dataset consisted of 13 Landsat 8 and 6 Landsat 9 OLI images.
5. How consistent are the relationships among the observations, including topology?
   For each image-acquisition date, Landsat Collection 2 Analysis Ready Data (ARD) and Level-2 science products were downloaded from the USGS EarthExplorer (https://earthexplorer.usgs.gov/) and USGS Earth Resources Observation and Science (EROS) Center Science Processing Architecture (ESPA) On Demand Interface (https://espa.cr.usgs.gov/), respectively.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Attn: USGS SPCMSC Data Management

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   gs-g-spcmsc_data_inquiries@usgs.gov
2. What's the catalog number I need to order this data set? nchan_coll2_shrln_20171222_20241115.shp, nchan_coll2_sandext_20171222_20241115.shp, nchan_coll2_vegext_20171222_20241115.shp, nchan_perp_transects_300m.shp, nchan_coll2_featmetrics_2017_2024.csv
3. What legal disclaimers am I supposed to read?
   Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	Download file contains vector sand, vegetation, shoreline, and 300m transect shapefiles (.shp) and comma-separated values (.csv) text files. in format shapefile, comma-delimited text
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P9HY3HOR/data/nchan_coll2_features.zip

   • Cost to order the data: None

5. What hardware or software do I need in order to use the data set?
   Vector datasets were created using Esri ArcGIS Pro version 3.3.2 and can be opened using Esri ArcGIS Pro version 3.1 or higher; these data may also be viewed using free Google Earth Pro or QGIS software.

Who wrote the metadata?

Dates:

Last modified: 19-Dec-2025

Metadata author:

U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

Attn: USGS SPCMSC Data Management

600 4th Street South

St. Petersburg, FL

USA

727-502-8000 (voice)

gs-g-spcmsc_data_inquiries@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)