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This page last updated: 05/19/2003
Metadata created using Minnesota Geographic Metadata Guidelines
| Originator | University of Minnesota | |||
| Abstract | This table contains estimates of lake water clarity for most lakes in the Twin Cities Metropolitan Area larger than 10 hectares (25 acres) for 10 different dates spanning a 25-year period from 1973 to 1998. These data were derived by developing, calibrating, and applying empirical models relating satellite spectral-radiometric data to available ground observations of Secchi depth transparency. | |||
| Browse Graphic | none available | |||
| Time Period of Content Date | ||||
| Currentness Reference | The data correspond to 10 different Landsat image dates: 7/3/73, 8/7/75, 9/6/83, 8/21/86, 8/26/88, 9/4/91, 8/24/93, 7/29/95, 7/15/96, and 9/7/98 | |||
| Access Constraints | None | |||
| Use Constraints | None | |||
| Distributor Organization | Metropolitan Council | |||
| Ordering Instructions | This dataset is distributed on the internet by clicking below after 'Online Linkage'. Doing so will tell your browser to download a 'ZIP' file which will contain the following: - dBase IV file - metadata for the dataset (.htm) - NOTICE.RTF, an important notice about this dataset that can be read by any word processing software. |
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| Distribution Liability | NOTICE: The Geographic Information System (GIS) Data to which this notice is attached are made available pursuant to the Minnesota Government Data Practices Act (Minnesota Statutes Chapter 13). THE GIS DATA ARE PROVIDED TO YOU AS IS AND WITHOUT ANY WARRANTY AS TO THEIR PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE. The GIS Data were developed by the Metropolitan Council for its own internal business purposes. The Metropolitan Council does not represent or warrant that the GIS Data or the data documentation are error-free, complete, current, or accurate. You are responsible for any consequences resulting from your use of the GIS Data or your reliance on the GIS Data. You should consult the data documentation for this particular GIS Data to determine the limitations of the GIS Data and the precision with which the GIS Data may depict distance, direction, location, or other geographic features. If you transmit or provide the GIS Data (or any portion of it) to another user, it is recommended that the GIS Data include a copy of this disclaimer and this metadata. | |||
| Online Linkage | I AGREE to the notice in "Distribution Liability" above. Clicking to agree will begin the download process (See Ordering Instructions above for details.) | |||
Go to Section:
1. Identification Information
2. Data Quality Information
3. Spatial Data Organization Information
4. Spatial Reference Information
5. Entity and Attribute Information
6. Distribution Information
7. Metadata Reference Information
| Section 1 | Identification Information | Top of page | ||
| Originator | University of Minnesota | |||
| Title | Satellite-Estimated Lake Water Clarity | |||
| Abstract | This table contains estimates of lake water clarity for most lakes in the Twin Cities Metropolitan Area larger than 10 hectares (25 acres) for 10 different dates spanning a 25-year period from 1973 to 1998. These data were derived by developing, calibrating, and applying empirical models relating satellite spectral-radiometric data to available ground observations of Secchi depth transparency. | |||
| Purpose | These data were developed as part of a regionally comprehensive lake water clarity assessment for the Twin Cities Metropolitan Area. | |||
| Time Period of Content Date | ||||
| Currentness Reference | The data correspond to 10 different Landsat image dates: 7/3/73, 8/7/75, 9/6/83, 8/21/86, 8/26/88, 9/4/91, 8/24/93, 7/29/95, 7/15/96, and 9/7/98 | |||
| Progress | Complete | |||
| Maintenance and Update Frequency | None planned | |||
| Spatial Extent of Data | The data span the entire seven-county metropolitan area of the Twin Cities | |||
| Bounding Coordinates | -94.012 -92.732 45.415 44.471 |
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| Place Keywords | Twin Cities, Anoka County, Carver County, Dakota County, Hennepin County, Ramsey County, Scott County, Washington County | |||
| Theme Keywords | Lake, Water, Water Clarity, Secchi Depth, Transparency, Water Quality | |||
| Theme Keyword Thesaurus | ||||
| Access Constraints | None | |||
| Use Constraints | None | |||
| Contact Person Information | Steve Kloiber,
Environmental Analyst Metropolitan Council 390 Robert Street North St. Paul, MN 55101 Phone: 651-602-1056 FAX: 651-602-1130 E-mail: steve.kloiber@metc.state.mn.us | |||
| Browse Graphic | none available | |||
| Browse Graphic File Description | ||||
| Associated Data Sets | Hydro_sub_luse2000 |
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| Section 2 | Data Quality Information | Top of full metadata | Top of page | |
| Attribute Accuracy | Synoptic water clarity estimates for an individual lake are generally accurate to within about 0.6 meters based on the standard error of the Y-estimate statistic from the regression model. For more information about the regression model and the accuracy of these estimates, please refer to the detailed citation (Kloiber 2002). | |||
| Logical Consistency | NA | |||
| Completeness | Estimates are provided for all lakes with greater than 10 hectares of open water provided the lake was deep enough to prevent signal confusion with macrophytes and bottom reflectance. Some large shallow lakes could not allways be assessed in this manner. Differences in water levels and vegetation growth result in missing estimates for some years on certain lakes. | |||
| Horizontal Positional Accuracy | NA - See metadata for the associated spatial dataset | |||
| Vertical Positional Accuracy | NA | |||
| Lineage | This table contains estimates of lake water clarity for most lakes in the Twin Cities Metropolitan Area larger than 10 hectares (25 acres) for 10 different dates spanning a 25-year period from 1973 to 1998. These data were derived by developing, calibrating, and applying empirical models relating satellite spectral-radiometric data to available ground observations of Secchi depth transparency. This work was performed on a Silicon Graphics Indigo workstation. The software used included ArcView 3.x GIS software and ERDAS Imagine image processing software. Ten high-quality, cloud-free Landsat images were selected from those available within a late summer index period (July 15 - September 15, with a preference for August). The images were registered to the Universal Transverse Mercator (UTM) coordinate system using the NAD 83 datum and subsequently resampled using nearest neighbor. Through careful selection of numerous (approx. 40), well-defined, and well-distributed ground control points (GCPs), the positional accuracy (RMSE) are on the order of +or- 0.25 pixels, or 7.5 m. An unsupervised cluster-classification of the Landsat image was performed first to differentiate water from terrestrial areas. All seven Landsat bands were used for the classification, and ten classes were specified. Because the spectral-radiometric response from water is significantly different from terrestrial features, water was assigned its own, easily identifiable class. The unsupervised classification map was then used as a binary mask to remove terrestrial areas from the original Landsat image. The resulting water-only image was used for further processing. The image is visually checked for cloud shadows and other anomalies and, if needed, affected areas are masked out of the image. An unsupervised classification of the water-only image is performed to differentiate water affected by varying concentrations of algae from water affected by vegetation, shoreline and/or bottom effects. Lake bathymetric maps, if available, and an unsupervised classification of the water-only image were used as guides when selecting area of interest (AOI) locations to avoid vegetation, shoreline, and bottom effects. The AOIs were manually delineated using the AOI tool in ERDAS Imagine. Once AOIs were delineated for all lakes in an image, a signature file was output containing the AOI average digital brightness levels for each of seven spectral bands. These data were then saved as a coma delimited text file and imported into Excel. An Excel macro was written to transform the data so it could be imported into MS Access. The data were imported into Access and joined to a table of ground observations of Secchi depth made within seven days of the satellite overpass (later processing restricted this to within one day of each overpass). The joined MS Access table was exported to a dBase file and then imported into SPSS version 10.0 for statistical analysis. A combination of linear regression techniques were used to develop the best model for each image using Band 1 (blue) and a ratio of Band 1 to Band 3 (blue:red) to estimate the natural log of Secchi depth in meters. The fitted models were applied to the Excel spectral signature file providing estimates of Secchi depth transparency for all lakes in the database. This file was then imported into ArcView and converted to an ArcView dBase file so that it could be joined to the lake sub-basin data layer. |
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| Source Scale Denominator | ||||
| Section 3 | Spatial Data Organization Information | Top of full metadata | Top of page | |
| Native Data Set Environment | dBase IV | |||
| Geographic Reference for Tabular Data | Thw PWI field from this table can be joined to the Subasin_id field of the Subasin Water Features Layer (Hydro_sub_luse2000) dataset. | |||
| Spatial Object Type | ||||
| Vendor Specific Object Types | ||||
| Tiling Scheme | All data are in one tile | |||
| Section 4 | Spatial Reference Information | Top of full metadata | Top of page | |
| Horizontal Coordinate Scheme | ||||
| Ellipsoid | ||||
| Horizontal Datum | ||||
| Horizontal Units | ||||
| Distance Resolution | ||||
| Section 5 | Entity and Attribute Information | Top of full metadata | Top of page | |
| Entity and Attribute Overview | PWI: A unique 8-digit lake ID that can be used to join this table the |
| Entity and Attribute Detailed Citation | Kloiber, S.M. 2002. Satellite Remote Sensing and Geographical Information Systems: Tools for Regional Surface Water Management. Ph.D. Thesis, University of Minnesota. 154 pages. | |||
| Section 6 | Distribution Information | Top of full metadata | Top of page | |
| Publisher | Metropolitan Council | |||
| Publication Date | 05/20/2003 | |||
| Contact Person Information | Mark Kotz GIS Database Administrator Metropolitan Council 390 Robert Street North St. Paul, MN 55101 Phone: 651-602-1644 FAX: 651-602-1674 E-mail: mark.kotz@metc.state.mn.us |
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| Distributor's Data Set Identifier | LakeWaterClaritySatelliteEstimated | |||
| Transfer Format Name | dBase IV table | |||
| Transfer Format Version Number | IV | |||
| Transfer Size | 1 MB for zip file | |||
| Ordering Instructions | This dataset is distributed on the internet by clicking below after 'Online Linkage'. Doing so will tell your browser to download a 'ZIP' file which will contain the following: - dBase IV file - metadata for the dataset (.htm) - NOTICE.RTF, an important notice about this dataset that can be read by any word processing software. |
|||
| Distribution Liability | NOTICE: The Geographic Information System (GIS) Data to which this notice is attached are made available pursuant to the Minnesota Government Data Practices Act (Minnesota Statutes Chapter 13). THE GIS DATA ARE PROVIDED TO YOU AS IS AND WITHOUT ANY WARRANTY AS TO THEIR PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE. The GIS Data were developed by the Metropolitan Council for its own internal business purposes. The Metropolitan Council does not represent or warrant that the GIS Data or the data documentation are error-free, complete, current, or accurate. You are responsible for any consequences resulting from your use of the GIS Data or your reliance on the GIS Data. You should consult the data documentation for this particular GIS Data to determine the limitations of the GIS Data and the precision with which the GIS Data may depict distance, direction, location, or other geographic features. If you transmit or provide the GIS Data (or any portion of it) to another user, it is recommended that the GIS Data include a copy of this disclaimer and this metadata. | |||
| Online Linkage | I AGREE to the notice in "Distribution Liability" above. Clicking to agree will begin the download process (See Ordering Instructions above for details.) | |||
| Section 7 | Metadata Reference Information | Top of full metadata | Top of page | |
| Metadata Date | 05/19/2003 | |||
| Contact Person Information | Steve Kloiber,
Environmental Analyst Metropolitan Council 390 Robert Street North St. Paul, MMN 55101 Phone: 651-602-1056 FAX: 602-1130 E-mail: steve.kloiber@metc.state.mn.us |
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| Metadata Standard Name | Minnesota Geographic Metadata Guidelines | |||
| Metadata Standard Version | 1.2 | |||
| Metadata Standard Online Linkage | http://www.gis.state.mn.us/stds/metadata.htm | |||
This page last updated: 05/19/2003