The Central African Republic Diamond Database (2018) - Hydrologically Corrected Digital Elevation Model (30 m)

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:

What does this data set describe?

Title:
The Central African Republic Diamond Database (2018) - Hydrologically Corrected Digital Elevation Model (30 m)
Abstract:
This is a 30 m digital elevation model (DEM) raster that was created by post-processing and hydrologically correcting the Shuttle Radar Topography Mission (SRTM) 30 m DEM. Procedures to create the DEM included mosaicking of multiple 30 m SRTM tiles, reprojection into UTM 34 N WGS 84 planar projection, an averaging filter to smooth out local variance in elevation values, conversion to float type, and improvements to hydrologic flow following the methods of Hellweger and Maidment (1997). For a complete description of the procedures used to create the DEM, see DeWitt and others (2018).
Supplemental_Information:
This dataset is closely associated with the Central African Republic Diamond Database (2018) - Hillshade dataset (30 m), published as part of the same On File Report.
  1. How might this data set be cited?
    DeWitt, Jessica D., Chirico, Peter G., and Bergstresser, Sarah E., 2018, The Central African Republic Diamond Database (2018) - Hydrologically Corrected Digital Elevation Model (30 m): U.S. Geological Survey, Reston, VA.

    Online Links:

    This is part of the following larger work.

    DeWitt, Jessica D., Chirico, Peter G., Bergstresser, Sarah G., and Clark, Inga E., 2018, The Central African Republic Diamond Database – A Geodatabase of Archival Diamond Occurrences and Areas of Recent Artisanal and Small-scale Diamond Mining: U.S. Geological Survey, Reston, VA.

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: 14.392089839578
    East_Bounding_Coordinate: 27.487792964054
    North_Bounding_Coordinate: 11.005474976683
    South_Bounding_Coordinate: 2.3280232001808
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2018
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GIS dataset
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference: Central African Republic
      This is a Raster data set.
    2. What coordinate system is used to represent geographic features?
      The map projection used is Transverse Mercator.
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: 21.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 30.0
      Ordinates (y-coordinates) are specified to the nearest 30.0
      Planar coordinates are specified in METERS
      The horizontal datum used is D_WGS_84.
      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?
    Entity_and_Attribute_Overview: The dataset is an example of a DEM
    Entity_and_Attribute_Detail_Citation:
    Environmental Systems Research Institute (ESRI). ESRI Support GIS Dictionary. (June 26, 2017). http://support.esri.com/other-resources/gis-dictionary.

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?
  3. To whom should users address questions about the data?
    Jessica D. DeWitt
    U.S. Geological Survey
    12201 Sunrise Valley Dr.
    Reston, VA
    USA

    703-648-6926 (voice)
    jdewitt@usgs.gov

Why was the data set created?

The purpose of this dataset is to model the physical topography of the Central African Republic (CAR) in a regular grid-format. The GIS raster dataset describes elevation values in meters (m) above sea level.

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: 2016 (process 1 of 4)
    Download of raw SRTM 30 m tiles covering the full extent of the Central African Republic (CAR) from the USGS Earth Explorer website (https://earthexplorer.usgs.gov).
    Date: 2016 (process 2 of 4)
    All SRTM tiles were mosaicked into one continuous raster dataset (30 m) then reprojected from the WGS 84 geographic coordinate system into the Universal Transverse Mercator (UTM) projected coordinate system (zone 34 N, WGS 84) in PCI Geomatica OrthoEngine (v. 2014) software.
    Date: Jul-2016 (process 3 of 4)
    Focal average statistics were calculated for a 5x5 window to smooth local variation from the raster, and the raster was converted from integer to float type using ESRI ArcGIS (v.10.4).
    Date: 2017 (process 4 of 4)
    Because the SRTM was created from radar data which is affected by dense vegetation, the thick canopy and undergrowth that grows in the stream valleys of CAR causes anomalously high elevation values in these areas and interferes with hydrologic flow. To resolve this issue, the major rivers of CAR were manually digitized as a new vector shapefile from the ESRI imagery basemap (ESRI, 2015) at scales 1:50,000 or coarser. This polyline file was converted to a 30 m raster with negative values, then used to vertically offset the pre-processed DEM and improve the modeling of hydrologic flow. These procedures roughly follow the the methods of Hellweger and Maidment (1997).
  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?
    No formal attribute accuracy tests were conducted
  2. How accurate are the geographic locations?
    No formal positional accuracy tests were conducted
  3. How accurate are the heights or depths?
    No formal positional accuracy tests were conducted
  4. Where are the gaps in the data? What is missing?
    Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: none
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Jessica D. DeWitt
    U.S. Geological Survey
    12201 Sunrise Valley Dr.
    Reston, VA
    USA

    7003-648-6926 (voice)
    jdewitt@usgs.gov
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    This dataset is formatted as a .tif raster. It requires the user to have geospatial software such as ESRI ArcGIS, Blue Marble Global Mapper, Que GIS, GRASS, or other GIS software.

Who wrote the metadata?

Dates:
Last modified: 05-Apr-2018
Metadata author:
Jessica D. DeWitt
U.S. Geological Survey
12201 Sunrise Valley Dr.
Reston, VA
USA

703-648-6926 (voice)
jdewitt@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Generated by mp version 2.9.47 on Thu Apr 5 06:44:46 2018