Data Sources & Acknowledgements
=============================

**TopoBathySim** relies on a federation of open-access geospatial datasets. We gratefully acknowledge the following agencies and specific surveys used for development, validation, and simulation.

The datasets are listed below in inverse order of priority (from global context to high-resolution survey truth).

Global Coverage (Tier 4)
------------------------

General Bathymetric Chart of the Oceans (GEBCO)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*   **GEBCO_2025 Grid**

    *   **Description**: A continuous terrain model for ocean and land, providing global context at 15 arc-second intervals.
    *   **Citation**: GEBCO Compilation Group (2025) GEBCO 2025 Grid (doi:10.5285/1c44ce9e-0a53-431f-9780-3843464522c5).
    *   **Access**: `GEBCO Grid Download <https://www.gebco.net/data_and_products/gridded_bathymetry_data/>`_

Continental / Land (Tier 3.5)
-----------------------------

U.S. Geological Survey (USGS) - 3DEP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*   **3D Elevation Program (3DEP)**

    *   **Description**: The source for high-quality topographic data of the conterminous United States, Hawaii, and U.S. territories.
    *   **Citation**: U.S. Geological Survey, 2017, 3D Elevation Program (3DEP): U.S. Geological Survey Fact Sheet 2017–3081.
    *   **Access**: `3DEP Homepage <https://www.usgs.gov/core-science-systems/ngp/3dep>`_

Regional Bathymetry (Tier 3)
----------------------------

NOAA NCEI - CUDEM
~~~~~~~~~~~~~~~~~

*   **Continuously Updated Digital Elevation Model (CUDEM)**

    *   **Description**: Ninth Arc-Second Resolution Bathymetric-Topographic Tiles. Used as a critical gap-filler for coastal inundation zones.
    *   **Citation**: Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder. 2014. Continuously Updated Digital Elevation Model (CUDEM) - Ninth Arc-Second Resolution Bathymetric-Topographic Tiles. NOAA National Centers for Environmental Information.
    *   **Access**: `Dataset Homepage <https://www.ncei.noaa.gov/metadata/geoportal/rest/metadata/item/gov.noaa.ngdc.mgg.dem:999919/html>`_ | `Bulk Access <https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/dem/NCEI_ninth_Topobathy_2014_8483/index.html>`_

Regional High-Resolution (Tier 2)
---------------------------------

NOAA Office of Coast Survey - BlueTopo™
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*   **BlueTopo™**

    *   **Description**: A compilation of the best available public bathymetric data of U.S. waters, merged into a simplified product.
    *   **Citation**: NOAA Office of Coast Survey. BlueTopo™.
    *   **Access**: `BlueTopo Portal <https://nauticalcharts.noaa.gov/data/bluetopo.html>`_

Local High-Resolution Lidar (Tier 1)
------------------------------------

NOAA National Geodetic Survey (NGS)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*   **Topobathymetric Lidar**

    *   **Description**: High-resolution nearshore bathymetry captured via green-wavelength Lidar.
    *   **Citation**: National Geodetic Survey, 2026: 2023 NOAA NGS Lidar DEM. NOAA National Centers for Environmental Information.
    *   **Example (Long Island Sound)**: `Methodology Report (PDF) <https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/10273/supplemental/NOAA_NY_Long_Island_Topobathymetric_Lidar_Imagery_Report_Final.pdf>`_
    *   **Access**: `NOAA Digital Coast <https://coast.noaa.gov/digitalcoast/>`_

    **Coverage Maximization & Survey Selection Strategy**

    To manage the hundreds of overlapping proprietary surveys available via NOAA's Digital Coast, TopoBathySim employs a dynamic **Spatial Index** to select the optimal data source for any given area of interest.

    When a simulation region intersects multiple available surveys, the system prioritizes them using the following **Fusion Hierarchy**:

    1.  **Vertical Datum Quality**: Surveys referenced to **NAVD88 (Geoid18)** are strictly preferred over legacy NAVD88 or Ellipsoidal references, ensuring consistent vertical integration with water levels.
    2.  **Recency**: Among surveys with equal datum quality, the most recently completed survey (based on ``end_date``) is selected.
    3.  **Spatial Overlap**: The system identifies all surveys intersecting the requested bounding box. Currently, the single "best" survey is selected to provide a self-consistent foundation, rather than blending multiple surveys which may have slight vertical offsets or temporal discrepancies.

    Within a selected survey, individual data tiles are fused using a **Mosaic** operation, where valid data overwrites NoData/Void areas.

Survey "Truth" Data (Tier 0)
----------------------------

NOAA NCEI - Bathymetric Attributed Grid (BAG)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*   **Bathymetric Attributed Grids (BAG)**

    *   **Description**: The definitive format for multi-beam sonar surveys. When found, these overwrite all other sources.
    *   **Citation**: NOAA National Centers for Environmental Information. "Bathymetric Attributed Grid (BAG) File Format."
    *   **Access**: `NCEI Bathymetry Data Viewer <https://www.ncei.noaa.gov/maps/bathymetry/>`_