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Everglades Depth Estimation Network (EDEN) October 2011 Digital Elevation Model (DEM)

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Frequently anticipated questions:


What does this data set describe?

Title:
Everglades Depth Estimation Network (EDEN) October 2011 Digital Elevation Model (DEM)
Abstract:
This is the 2nd release of the fourth version of an Everglades Depth Estimation Network (EDEN) digital elevation model (DEM) generated from certified airborne height finder (AHF) and airboat collected ground surface elevations for the Greater Everglades Region. Collectively, these data are referred to as "High Accuracy Elevation Data" (HAED). Inconsistencies in available greater Everglades boundary files resulted in a missing elevation value for 1 cell along the western boundary of WCA3s. In this release, that single cell was "filled" with a value of 2.19682 meters as determined through the kriging process summarized below. As was the case with the 1st release (EDEN_em_JA10), this version differs from the previous elevation model (EDEN_EM_OCT07) in several ways. First, the kriging algorithm applied to newly modeled subareas was changed from ordinary to universal kriging - resulting in slightly lower errors during cross-validation and accuracy assessment. Second, a previously omitted area in the northwestern corner of the Everglades National Park (ENP) and southern portion of Big Cypress National Preserve has been filled. Third, to increase accuracy in WCA1, the most challenging EDEN subarea from an elevation modeling standpoint, the Conservation area is subdivided into 4 zones (Northern, Central, Southwest and Southeast). Boundaries between the North, Central and two Southern zones is based upon landscape units defined through the CERP. The landscape unit representing approximately the southern third of WCA1 was further divided into two zones (east and west) based on marked changes in slope and aspect data generated from a DEM of the southern landscape unit as a whole. Division of WCA1 into 5 zones reduces errors estimated by comparing DEM modeled water depths with those measured by EDEN Principal Investigators in the field. Subdivision of the south landscape unit into east and west zones resulted in lower error estimates for the eastern subzone (i.e., southeast) without significantly affecting (i.e., improving or degrading) the quality of the western subzone - an area where DEM modeling is most challenging. Finally, to reduce artificial breaks in elevation along WCA1 subarea boundaries, models were overlapped by 1 cell at these boundaries and, for the North, Central and South zone boundaries, overlapping model values were averaged. For the boundaries between the Southwest and Southeast zones, cell values were "blended" based on weighted distance from the boundary edge. Finally, points along the North / Central and Central / South zone edges were subjectively selected and changed by adding or subtracting 0.03 meters (3 cm) to particular cells. This slightly reduces apparent artifacts without drastically affecting the integrity of the model. The EDEN offers a consistent and documented dataset that can be used to guide large-scale field operations, to integrate hydrologic and ecological responses, and to support biological and ecological assessments that measure ecosystem responses to Comprehensive Everglades Restoration Plan. To produce historic and near-real time maps of water depths, the EDEN requires a system-wide DEM of the ground surface.
  1. How should this data set be cited?

    U.S. Geological Survey, 201110, Everglades Depth Estimation Network (EDEN) October 2011 Digital Elevation Model (DEM).

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81.37
    East_Bounding_Coordinate: -80.22
    North_Bounding_Coordinate: 26.69
    South_Bounding_Coordinate: 25.22

  3. What does it look like?

    <https://sofia.usgs.gov/eden/images/maps/EDEN_oc11_release_graphic_lg.gif> (GIF)
    graphic showing the coverage of EDEN_EM_OC11
    <https://sofia.usgs.gov/publications/fs/2006-3087/images/figure2.jpg> (JPEG)
    location of Everglades Depth Estimation Network (EDEN) gaging stations
    <http://www.evergladesplan.org/pm/recover/recover_docs/map/MAP_3.1_GE.pdf> (pdf)
    p. 3-38 shows the a satellite image with the landscape units of Greater Everglades wetlands to be used for stratified random sampling design
    graphic showing locations of new models

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

    Beginning_Date: 1995
    Ending_Date: Aug-2007
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: raster digital data

  6. How does the data set represent geographic features?

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

      Indirect_Spatial_Reference: Greater Everglades region
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 405 x 287 x 1, type Grid Cell

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -81
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using Row and Column
      Abscissae (x-coordinates) are specified to the nearest 400
      Ordinates (y-coordinates) are specified to the nearest 400
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: .15
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?


Who produced the data set?

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

    • U.S. Geological Survey

  2. Who also contributed to the data set?

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

    John W. Jones
    U.S. Geological Survey
    521 National Center
    Reston, VA 20192
    USA

    703 648-5543 (voice)
    703 648-4165 (FAX)
    jwjones@usgs.gov


Why was the data set created?

These data were specifically created for the development of water depth information using interpolated water surfaces from the EDEN stage data network.


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: 2009 (process 1 of 1)
    The EDEN domain was broken into a large number of equal-sized rectangles (cells) that in total are referred to as the "grid". Characteristics of this grid, such as location of the centroid, the representative area of the Everglades, elevation, and percentage of vegetation type, define the grid spatial parameters. To match the Airborne Height Finder (AHF) data sampling spacing, the spatial resolution or the dimension (in ground distance) of each grid cell is 400 meters on each side. The ground surface DEM development process is iterative as additional high accuracy elevation data (HAED) are collected, water surfacing algorithms improve, and additional ground-based ancillary data become available. This version was produced by using all available AHF points posted to SOFIA as of August 2007.
    To create a realistic region-wide elevation model for EDEN purposes, the elevation data were segregated by Water Conservation Areas and National Park boundaries so that local trends could be isolated, sub-region specific interpolation models could be developed, and realistic breaks in elevation along sub-region boundaries could be imbedded in a final, region-wide DEM.
    For the previous release of the DEM, subarea DEMs were produced using the geostatistical approach called "anisotropic ordinary kriging". This version is composed of new models created for each new EDEN subarea in Water Conservation Area 1 (WCA1) and for the new coverage in the southern portion of BCNP and the northwest corner of the ENP. For the latest iteration of the EDEN DEM "anisotropic universal kriging" was employed.
    As with the previously released DEM, WCA1 surfaces were produced by removing all "upland" AHF points. However, in this version WCA1 "upland" was defined through a reclassification of the South Florida Water Management Vegetation Map rather than the Florida GAP map.
    As the most challenging area from an elevation modeling standpoint, for this revision WCA1 was further subdivided into a total of 4 zones. First, boundaries between the North, Central and two South zones are based upon landscape units defined through the CERP Monitoring and Assessment Plan, Part 1 (Figure 3-20). Then the South landscape unit (representing approximately the southern third of WCA1) was further divided into two zones (east and west, termed "Southeast" and"Southwest") based on marked changes in slope and aspect data that were generated from a DEM of the South landscape unit as a whole. Division of WCA1 into 4 zones reduces errors estimated by comparing DEM modeled water depths with those measured by EDEN Principal Investigators in the field. Subdivision of the south landscape unit into east and west zones resulted in lower error estimates for the Southeast zone without significantly affecting (i.e., improving or degrading) the quality of the Southwest zone - an area where DEM modeling is most challenging.
    A previously omitted area in the southern portion of the Big Cypress National Preserve (BCNP) and the northwestern corner of the Everglades National Park (ENP) has been filled.

    Person who carried out this activity:

    John Jones
    U.S. Geological Survey
    521 National Center
    Reston, VA 20192
    USA

    703 648-5543 (voice)
    703 648-4165 (FAX)
    jwjones@usgs.gov

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

    Telis, Pamela, 2006, The Everglades Depth Estimation Network (EDEN) for support of ecological and biological assessments: USGS Fact Sheet 2006-3087, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

    Other_Citation_Details: accessed as of 12/29/2009
    Jones, J. W., 2001, Image and in situ data integration to derive sawgrass density information for surface-flow modeling in the Everglades: International Association of Hydrological Sciences, Wallingford, Oxfordshire, UK.

    Other_Citation_Details:
    in Remote Sensing and Hydrology 2000, editors Manfred Owe, Kaye Brubaker, Jerry Ritchie, and Albert Rango, publication 267, ISBN 1-901502-46-5
    Desmond, G. B., 2003, Measuring and mapping the topography of the Florida Everglades for Ecosystem Restoration: USGS Fact Sheet 021-03, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details: accessed as of 1/11/2010
    U.S> Army Corps of Engineers, 2004, RECOVER: Monitoring and Assessment Plan (MAP) 2004 Greater Everglades Wetlands Module: U.S. Army Corps of Engineers, Jacksonville, FL.

    Online Links:

    Other_Citation_Details: accessed as of 2/3/2010


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?

    Horizontal positions are established by GPS observations and are referenced to the North American Datum of 1983 (NAD83). The desired horizontal accuracy is +/- 15 centimeters. This level of accuracy is consistent with GPS differential techniques which use two stations - a high-quality dual-frequency GPS receiver base station and a roving GPS station. The density and accuracy of a given GPS data observation varies from a few meters to a few centimeters according to the Position Dilution of Precision (PDOP) in the study area. Generally if the PDOP is observed to be excessive, data collection is discontinued or the data are discarded. The PDOP is an indicator of the positional accuracy of the GPS that be can derived from the current GPS satellite geometry, which varies continuously. Generally the smaller the PDOP number, the higher the data quality. The PDOP is a permanent part of the recorded data and is also included in the post processing procedures during reduction of the GPS observations to NAD 83. Where possible, the GPS base station has an ellipsoid height to an accuracy of two centimeters relative to the Continuously Operating Reference Stations (CORS) or the High Accuracy Reference Network (HARN), both operated by the National Geodetic Survey (NGS).

  3. How accurate are the heights or depths?

    Source data (HAED) collected to better than +/- 15cm. Standard errors of cross-validation for the DEM range from ~7cm to ~21cm depending on the EDEN subarea.

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

    Ground-surface elevation data were collected by the USGS at more than 50,000 points with an approximate spacing of 400 meters covering almost the entire Greater Everglades. The EDEN water-level network consists of hourly water-level data from 253 gaging stations (230 existing gaging stations and 23 new installations) and includes freshwater (nontidal) marsh gaging stations, boundary gages on canals, and coastal gaging stations operated by the Big Cypress National Preserve (BCNP), Everglades National Park (ENP), South Florida Water Management District (SFWMD), and USGS. The U.S. Army Corps of Engineers (USACE) and SFWMD recently documented or surveyed a majority of the hydrologic gages in the Greater Everglades to obtain correct values for converting water-level data from NGVD 29 to NAVD 88. The NAVD 88 datum is consistent in comparing water-level data across the Greater Everglades and computing accurate water depths.

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

    The EDEN monitoring network includes ground-elevation measurements and continuous water-level data.


How can someone get a copy of the data set?

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

Access_Constraints:
These data were produced for EDEN operational water depth estimation and applications.
Use_Constraints:
The user is cautioned that this elevation model was produced specifically for EDEN applications and is based on input data of approximately 400m sample spacing and +/- 15cm vertical accuracy. No statement of appropriateness for uses other than that intended are implied.

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

    Heather S. Henkel
    U.S. Geological Survey
    600 Fourth St. South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext 3028 (voice)
    727 803-2030 (FAX)
    hhenkel@usgs.gov

  2. What's the catalog number I need to order this data set?

    EDEN_EM_ JA10

  3. What legal disclaimers am I supposed to read?

    No warrantees are implied or explicit for the data

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 27-Oct-2011
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

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


Generated by mp version 2.9.14 on Thu Oct 27 14:12:14 2011

U.S. Department of the Interior, U.S. Geological Survey
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