Shaded Relief (1:5,000)

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Frequently anticipated questions:

What does this data set describe?

Title: Shaded Relief (1:5,000)
Abstract:
This raster layer, useful for cartographic display, represents a shaded relief or "hillshade" for the surface terrain of Massachusetts. Its source data were the digital terrain models that were produced as part of the 1:5,000 Black and White Digital Orthophoto imagery project. Cellsize is 10 meters by 10 meters. Each cell has a grayscale value ranging from 1 to 255.
MassGIS stores the statewide image in its Oracle-based ArcSDE geodatabase as IMG_SHDREL5K.
  1. How might this data set be cited?
    MassGIS, EOEA -, 20050228, Shaded Relief (1:5,000).

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.545863
    East_Bounding_Coordinate: -69.870162
    North_Bounding_Coordinate: 42.909573
    South_Bounding_Coordinate: 41.197561
  3. What does it look like?
    (PNG)
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 28-Feb-2005
    Currentness_Reference: publication date
  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?
      This is a Raster data set. It contains the following vector data types (SDTS terminology):
      • G-polygon (44)
      It contains the following raster data types:
      • Dimensions 18821 x 30022 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Lambert Conformal Conic.
      Projection parameters:
      Standard_Parallel: 42.683333
      Standard_Parallel: 41.716667
      Longitude_of_Central_Meridian: -71.500000
      Latitude_of_Projection_Origin: 41.000000
      False_Easting: 200000.000000
      False_Northing: 750000.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 10.000000
      Ordinates (y-coordinates) are specified to the nearest 10.000000
      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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 1
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Implicit coordinate
  7. How does the data set describe geographic features?
    shdrel5k.sid.vat
    OID
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Value
    Count

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?
    EOEA - MassGIS
    Attn: Michael Trust
    Sr. Database Administrator
    251 Causeway Street
    Boston, MA
    USA

    (617) 626-1000 (voice)
    (617) 626-1249 (FAX)
    michael.trust@state.ma.us
    Hours_of_Service: 9 AM - 5 PM

Why was the data set created?

Cartographic display

How was the data set created?

  1. From what previous works were the data drawn?
    (source 1 of 1)
    Source_Scale_Denominator: 1:5,000
    Source_Contribution:
    Using ESRI's ArcInfo Workstation software, MassGIS ran the TOPOGRID command, using the existing 3-Meter Elevation Contours (1:5,000) layer as input. Working on an Orthophoto Quad Index tile-by-tile basis (clipping the contours out of SDE with a bit of overlap on all sides of the tile), TOPOGRID produced elevation grids based on the contours. The HILLSHADE command then produced the shaded relief grid from the output of TOPOGRID. The hillshade grids were produced with an azimuth of 315 degrees, an altitude of 45 degrees, a Z factor of 1.5, and without the effects of local shadows. To produce a continuous coastline, the outermost breaklines from the Topographic Breaklines layer were appended and edited into polygon coverages, converted to grids, and used the in the SELECTMASK () Grid function. This process allowed all off-shore areas to be coded as NODATA. For some tiles along the coast, there were too few contours to use TOPOGRID. For these, an OQ tile-based area was clipped out of the Digital Elevation Model (1:5,000) and HILLSHADE was run on that. Once grids for all tiles were completed, they were merged into one statewide grid. At this point, any grayscale values of 255 (pure white) within the land portion of the image were changed to 254 and all NODATA was converted to 255 so that when the grid was converted to a tiff image (needed for production of a MrSID image version of the layer), the only 255s would be offshore or in adjacent states, allowing for a white background around valid hillshade data. The grid version was loaded into SDE, after which pyramids were built and statistics generated.
    After some experimentation, the TOPOGRID-HILLSHADE approach was chosen over other methods (such as the Surface Analysis > Hillshade tool in ArcGIS' Spatial Analysis extension) because the HILLSHADE command produced the smoothest, most realistic and cartographically pleasing shaded relief image when generated from the already generalized contours, with minimal banding or other visually disturbing artifacts. In a few areas, some banding may be noticeable at large scales, a result of the irregular pattern of original sampling points in the source DTM files.
  2. How were the data generated, processed, and modified?
    (process 1 of 1)
    Metadata imported. Data sources used in this process:
    • C:\temp\img_shdrel5k.xml
  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?
    The source digital terrain model data were collected on analytical stereoplotters at a sufficient density to support generation of 3-meter contours conforming to the National Map Accuracy Standards (+ or - 1.5 meters) at the nominal scale of 1:5,000.
  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 observations, including topology?

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: None
  1. Who distributes the data set? (Distributor 1 of 1)
    EOEA - MassGIS
    Attn: Michael Trust
    Sr. Database Administrator
    251 Causeway Street
    Boston, MA
    USA

    (617) 626-1000 (voice)
    (617) 626-1249 (FAX)
    michael.trust@state.ma.us
    Hours_of_Service: 9 AM - 5 PM
  2. What's the catalog number I need to order this data set? Data may be ordered in MrSID image format
  3. What legal disclaimers am I supposed to read?
    Please see the "PURCHASE AGREEMENT FOR DIGITAL DATA PROVIDED BY THE MASSACHUSETTS EXECUTIVE OFFICE OF ENVIRONMENTAL AFFAIRS", online at http://www.mass.gov/mgis/puragree.htm.
  4. How can I download or order the data?
  5. Is there some other way to get the data?
    Order CD-ROM from http://www.mass.gov/mgis/order.htm
  6. What hardware or software do I need in order to use the data set?
    MassGIS' data may be used in many standard GIS software products. See each software's vendor for technical prerequisites.

Who wrote the metadata?

Dates:
Last modified: 14-Mar-2014
Metadata author:
EOEA - MassGIS
Attn: Michael Trust
Sr. Database Administrator
251 Causeway Street
Boston, MA
USA

(617) 626-1000 (voice)
(617) 626-1249 (FAX)
michael.trust@state.ma.us
Hours_of_Service: 9 AM - 5 PM
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Generated by mp version 2.9.33 on Wed Jun 08 13:50:26 2016