Impervious Surfaces, Island of Niihau

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Frequently anticipated questions:


What does this data set describe?

Title: Impervious Surfaces, Island of Niihau
Abstract:
This data set identifies impervious surfaces on the island of Niihau. Impervious surfaces have been extracted using semi-automated methods from high resoltion imagery.
  1. How should this data set be cited?

    State of Hawaii, Office of Planning, and Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC), 20071130, Impervious Surfaces, Island of Niihau: State of Hawaii, Office of Planning, Honolulu, Hawaii.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -160.247233
    East_Bounding_Coordinate: -160.048764
    North_Bounding_Coordinate: 22.022604
    South_Bounding_Coordinate: 21.718297

  3. What does it look like?

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

    Calendar_Date: 2005
    Currentness_Reference: publication date

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

    Geospatial_Data_Presentation_Form: remote sensing image

  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 raster data types:

      • Dimensions 13974 x 8441 x 1, type Pixel

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 4
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -159.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using Row and Column
      Abscissae (x-coordinates) are specified to the nearest 2.400000
      Ordinates (y-coordinates) are specified to the nearest 2.400000
      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 1/298.257224.

  7. How does the data set describe geographic features?

    Layer_1
    Island of Niihau delineated by igh resolution multispectral imagery. (Source: unknown)

    Value
    0 or 1 indicates whether pixel is impervious or not. (Source: State of Hawaii, Impervious Mapping Project.)

    ValueDefinition
    0 PerviousFeatures which allow infiltration from precipitation.
    1 ImperviousAnthropogenic features such as buildings, parking lots and roads developed from asphalt, concrete or other constructed surfaces which do not allow infiltration from precipitation.


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?

    State of Hawaii, Office of Planning
    Attn: Joan Delos Santos
    Systems Analyst, GIS Program
    P.O. Box 2359
    Honolulu, Hawaii 96804
    USA

    808 587 2895 (voice)
    808 587 2899 (FAX)
    jdelos_santos@dbedt.hawaii.gov

    Hours_of_Service: 7:45 am to 4:30 pm HST, M-F


Why was the data set created?

To create a baseline inventory of impervious surfaces which can be utilized by state and local resource managers to assess the impacts precipitation events on water quality and flooding.


How was the data set created?

  1. From what previous works were the data drawn?

    COAST (source 1 of 1)
    www.sanborn.com., Sanborn., 20070515, Island of Niihau Impervious Surfaces Map.: State of Hawaii, Office of Planning, Honolulu, HI.

    Online Links:

    Type_of_Source_Media: ArcInfo coverage file
    Source_Contribution:
    Original source coverage from which data layer was clipped to Niihau.

  2. How were the data generated, processed, and modified?

    Date: 30-Nov-2007 (process 1 of 1)
    This dataset was created by the Sanborn Mapping Company. The impervious surface classification is based on high resolution multispectral imagery. The study area for the project was the island of Niihau, U.S. Hawaiian Island Chain. Automated Classification: The first step in the classification methodology involved incorporating automated techniques. Sanborn analysts utilized the Feature Analyst software extension to extract impervious surfaces from the igh resolution multispectral imagery. This was performed by providing the software with photo-interpreted polygon examples which "train" the software's learning mechanism to recognize impervious surface features for extraction from the imagery. The software then provides the user with an automated output which can be accepted by the analyst or retrained for an improved result. This automated output captures a large percentage of the existing impervious surface features within the imagery but does not meet the required accuracy. Classes: 0 - Pervious; 1 - Impervious

    Person who carried out this activity:

    State of Hawaii, Office of Planning
    Attn: Joan Delos Santos
    Systems Analyst, GIS Program
    P.O. Box 2359
    Honolulu, HI 96804
    USA

    808 587 2895 (voice)
    808 587 2899 (FAX)
    jdelos_santos@dbedt.hawaii.gov

    Hours_of_Service: 7:45 am to 4:30 pm HST, M-F
  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?

    Treating the map as a binary or single class scheme, impervious/pervious, allows for a simpler sampling technique than a traditional thematic land cover assessment. For this product, Sanborn developed an efficient procedure to assess accuracy of the impervious classification. The desired accuracy is at least 85% for the impervious/pervious map of Niihau. The approach described here tested the map for an accuracy of 90% for a MMU of 0.06 acre. Since Sanborn was working with a two-case situation they only needed to know whether the classification was right or wrong, a binomial distribution was used to calculate the sample size. Using that assumption, Sanborn used Ginevan (1979) who illustrated a sampling method using stratified random points that satisfies three criteria: 1. The scheme should have a low probability of accepting a map of low accuracy. 2. It should have a high probability of accepting a map of high accuracy. 3. It should require a minimum number of ground truth samples. Using the look-up table given in the paper that presents the required sample size for a given minimum error and a desired level of confidence, Sanborn determined the specific number of points that are required to meet the accuracy specification. To validate a map to determine if it meets a thematic accuracy of 90%, with a 95% confidence level (a 95% confidence interval means the chance of 1 in 20 of rejecting a map that is actually correct), the minimum number of sites required was 298; with the map being rejected if more than 21 are misclassified. In order to compensate for the rarity of impervious surfaces over a large portion of the Niihau landscape, the approach was to create 3 strata layers in order to limit the selection process to areas of likely impervious, and produce a map that accurately assesses the usefulness of the map to the user. Strata 1: Impervious Features This strata layer is based on the actual classification of impervious features. Strata 2: Distance buffer from impervious map The presence of impervious surfaces are correlated with other impervious features, and are likely to occur near other impervious features. A distance map based on a buffer of 250 m will be used to sample from. Strata 3: Remaining un-sampled area. Each of the strata was sampled to build an assessment database that exceeds the required minimum of 298 assessment points. The goal for the division of accuracy assessment points was an approximate 50:50 (impervious:pervious) stratification. The break down is as follows. Table 1: Sampling breakdown based on strata layer. Strata Layer, Percentage of Total Samples, Target Number of Samples; Impervious Classification 30 greater than 149; Distance From Impervious feature Mask 25 greater than 75; Remaining Un-sampled Area 25 greater than 74; Areas of impervious or where impervious surfaces are expected were biased in the sampling structure. Once the samples are collected, labeling and quality control procedures were completed on the samples to create a final accuracy database. The result was a simplified confusion matrix where only two classes are categorized. An overall accuracy statement can be made by summing the correct accuracy locations and deriving a percentage relative to the total number of accuracy points. References: Congalton, R.G., Kass Green 1999. Assessing the accuracy of remotely sensed data: principles and practices. CRC/Lewis Press, Boca Raton, FL. (In Press); Congalton, R. G. and R. D. Macleod. 1998. A quantitative comparison of change-detection algorithms for monitoring eelgrass from remotely sensed data. Photogrammetric Engineering and Remote Sensing. Vol. 64, No. 3, March 1998, pp. 207-216.; Ginevan, M.E. 1979. Testing land-use map accuracy: another look. Photogrammetric Engineering and Remote Sensing, 45(10): 1371-1377.

  2. How accurate are the geographic locations?

    Accuracy dependant on source data

  3. How accurate are the heights or depths?

    Not applicable

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

    Data set is complete.

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

    Tests for logical consistency indicate that all row and column positions in the selected latitude/longitude window contain data. Conversion and integration with vector files indicates that all positions are consistent with earth coordinates covering the same area. Attribute files are logically consistent.


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:
Although every effort has been made to ensure the accuracy of information, errors and conditions originating from physical sources used to develop the State of Hawaii GIS database may be reflected in the data supplied. The user must be aware of data conditions and bear responsibility for the appropriate use of the information with respect to possible errors, original map scale, collection methodology, currency of data, and other conditions specific to certain data. The GIS data or cartographic digital files are not a legal representation of any of the features which they depict. No warranty expressed or implied is made by State of Hawaii GIS program regarding the accuracy or utility of this information.

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

    State of Hawaii, Office of Planning
    Attn: Joan Delos Santos
    Systems Analyst, GIS Program
    P.O. Box 2359
    Honolulu, Hawaii 96804
    USA

    808 587 2895 (voice)
    808 587 2899 (FAX)
    jdelos_santos@dbedt.hawaii.gov

    Hours_of_Service: 7:45 am to 4:30 pm HST, M-F
  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Although every effort has been made to ensure the accuracy of information, errors and conditions originating from physical sources used to develop the State of Hawaii GIS database may be reflected in the data supplied. The user must be aware of data conditions and bear responsibility for the appropriate use of the information with respect to possible errors, original map scale, collection methodology, currency of data, and other conditions specific to certain data. The GIS data or cartographic digital files are not a legal representation of any of the features which they depict. No warranty expressed or implied is made by State of Hawaii GIS program regarding the accuracy or utility of this information.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 20-Dec-2012
Last Reviewed: 24-Sep-2010
Metadata author:
State of Hawaii, Office of Planning
Attn: Joan Delos Santos
Systems Analyst, GIS Program
P.O. Box 2359
Honolulu, Hawaii 96804
USA

808 587 2895 (voice)
808 587 2899 (FAX)
jdelos_santos@dbedt.hawaii.gov

Hours_of_Service: 7:45 am to 4:30 pm HST, M-F
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.9.13 on Fri Oct 31 10:41:00 2014