Alaska Highway GPS Centerline Data

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Frequently anticipated questions:


What does this data set describe?

Title: Alaska Highway GPS Centerline Data
Abstract:
This coverage, created by the Alaska Department of Transportation and Public Facilities Statewide GIS Mapping Section, depicts the roadway centerlines for the major highways in Alaska . The centerline data was collected using a Trimble Pro XR DGPS receiver during the summer of 1997 to the fall of 1999. The raw centerline data was exported from Trimble's Pathfinder Office software into ARC/INFO where it was converted into an arc coverage, edited, attributed, and projected.
  1. How should this data set be cited?

    State of Alaska - Department of Transportation and Public Facilities, 19991117, Alaska Highway GPS Centerline Data: Department of Transportation and Public Facilities / Statewide GIS Mapping Section, Juneau, Alaska.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -152.413411
    East_Bounding_Coordinate: -126.320875
    North_Bounding_Coordinate: 68.453186
    South_Bounding_Coordinate: 59.052109

  3. What does it look like?

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

    Beginning_Date: 01-May-1997
    Ending_Date: 01-Sep-1999
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: map

  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. It contains the following vector data types (SDTS terminology):

      • Complete chain (1012)
      • Point (4)

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

      The map projection used is Albers Conical Equal Area.

      Projection parameters:
      Standard_Parallel: 55.000000
      Standard_Parallel: 65.000000
      Longitude_of_Central_Meridian: -154.000000
      Latitude_of_Projection_Origin: 50.000000
      False_Easting: 0.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.002048
      Ordinates (y-coordinates) are specified to the nearest 0.002048
      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.

  7. How does the data set describe geographic features?

    gps_akhwysy.aat

    LAYER
    Characterizes the quality of the GPS centerline data.

    ValueDefinition
    ROADCENTERLINEGPS Centerline data (final product)
    ROADCENTERLINE_BADCorrupt GPS centerline data (will need to re-collect road segment)
    ROADCENTERLINE_UNCORUncorrected GPS centerline data (no correction data available, will need to re-collect road segment)
    USGS 1:25,000United States Geological Survey Digital Line Graph roadway data 1:25,000 scale.

    NAME
    Signed name that appeared on the road during GPS collection or name assigned to the road by the Alaska Department of Transportation and Public Facilities Statewide Traffic Data Section.

    CDSNUM
    Unique route identification number assigned by the Alaska Department of Transportation and Public Facilities Statewide Traffic Data Section

    LNGTHML
    Length of arc segment in miles.


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?

    State of Alaska - Department of Transportation and Public Facilities - Statewide GIS Mapping Section

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

    Garry Remsberg, Jr.
    State of Alaska - Department of Transportation and Public Facilities
    Cartographer II
    Planning Division - Statewide GIS Mapping Section 3132 Channel Drive, MS/2500
    Juneau, Alaska 99801-7898
    USA

    907-465-8956 (voice)
    907-465-6984 (FAX)
    gis@dot.state.ak.us


Why was the data set created?

The Alaska Department of Transportation and Public Facilities Statewide GIS Mapping Section collected the DGPS centerline data and created this centerline coverage in an effort to establish a current, accurate digitial transportation data set for the state.


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?

    The road centerline data was collected using a twelve channel Trimble Pro XR receiver with a Trimble TSC1 data logger running Trimble's Asset Surveyor software. Centerlines were captured as line features with a collection interval of one position per second. All rover files were differentially corrected with the best available base station data.
    Trimble specifies the Pro XR receiver as capable of delivering differentially corrected C/A code position accuracy to better than 50 centimeters (RMS) horizontal. The 50 centimeter level of horizontal accuracy is obtained only under optimal operating circumstances. The accuracy of each determined position may be greatly degraded by many factors. Factors that degrade accuracy may include but are not limited to atmospheric interference, satellite geometry, satellite clock errors, satellite orbit errors, topography, receiver noise, and multipathing errors.
    Since our road centerline data was collected in very dynamic driving conditions it is not possible to make a blanket statement of accuracy. However, Trimble's Pathfinder Office software does provide tools to predict the precision of both individual observations and entire features. Trimble's precision estimates are RMS based. Average horizontal 2dRMS values for our road centerline data range from four to eight feet. Precision estimates should be used as a gauge of quality and repeatability and not be misconstrued as a measurement to or from true feature location.

  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 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:
Limitations of Data. Acknowledgment of the Alaska Department of Transportation and Public Facilities, Statewide GIS Mapping Section would be appreciated in products derived from these data sets. Any hardcopies or published datasets utilizing these data sets shall clearly indicate their source. If the user has modified the data in any way they are obligated to describe the types of modifications they have performed. User specifically agrees not to misrepresent these data sets, nor to imply that changes they made were approved by the Alaska Department of Transportation and Public Facilities. Any hardcopies or published datasets utilizing these data sets shall clearly indicate their source. If the user has modified the data in any way they are obligated to describe the types of modifications they have performed. User specifically agrees not to misrepresent these data sets, nor to imply that changes they made were approved by the Alaska Department of transportation and Public Facilities.

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

    Garry Remsberg, Jr.
    Alaska Department of Transportation and Public Facilities
    Cartographer II
    Planning Division - Statewide GIS Mapping Section 3132 Channel Drive, MS/2500
    Juneau, Alaska 99801-7898
    USA

    907-465-8956 (voice)
    907-465-6984 (FAX)
    gis@dot.state.ak.us

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

  3. What legal disclaimers am I supposed to read?

    Although this data set has been processed successfully on a computer system at the State of Alaska, Department of Transportation and Public Facilities, Statewide GIS Mapping, no warranty expressed or implied is made by the State of Alaska regarding the utility of the data on any system, nor shall the act of distribution constitute such a warranty. The State of Alaska and Department of Transportation and Public Facilities makes no expressed or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user purposes. In no event will the State of Alaska and/or The Department of Transportation and Public Facilities be liable for any incidental, indirect, special, consequential or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof or otherwise, and in no event will the State of Alaska and/or The Department of Transportation and Public Facilities liability to the requestor or anyone else exceed the fee paid for the electronic service or product.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 11-Aug-2000
To be reviewed: 17-Nov-2000
Metadata author:
Garry Remsberg, Jr.
State of Alaska - Department of Transportation and Public Facilities
Cartographer II
Planning Division - Statewide GIS Mapping Section 3132 Channel Drive, MS/2500
Juneau, Alaska 99801-7898
USA

907-465-8956 (voice)
907-465-6984 (FAX)
gis@dot.state.ak.us

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


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