The following tests were also applied in order to minimize the number of or invalid or illogical code assignments:
1. FEATURE_ID must be unique and persistent, though not necessarily sequential without breaks.
2. Potential wetlands cannot be anything but a Lake or Pond (STATUS_ID = 3 and FEAT_TYPE_ID <> 421 must be a empty set)
3. Current Reservoirs cannot be Non water (FEAT_TYPE_ID = 101 and WATER_ID = 0 and RATE_ID = 1 must be an empty set).
This test was also peformed for FEAT_TYPE_ID = 106 Fish hatchery 109 Industrial or residential water impoundment 115 Flats (tidal, mud, sand, gravel) 116 Bays, estuaries, gulfs, oceans 400 Rapids 401 Falls 412 Dam, wier or obscured 414 River or stream 415 Aqueduct 416 Flume 421Lake or pond
4. Current Dam, wier or obscured cannot be Water (FEAT_TYPE_ID = 406 and WATER_ID = 1 and RATE_ID = 1 must be an empty set).
This test was also performed for FEAT_TYPE_ID = 423 Sand and gravel 902 Fresh water island 901 Marine Island
5. Potential wetlands must be Water (STATUS_ID = 3 and WATER_ID = 0 must be empty)
6. Various test were performed where wildcard queries on the NAME item were compared to the FEAT_TYPE assigned. Though these tests are not absolute due to the way certain features are named, it did allow a search for major blunders.
7. A BIGWATER river must be a RIVER/STREAM type (SUBSET_ID =1 and FEAT_TYPE_ID <> 412 must be empty). The exception are FLUMES which are considered connecting segments of a river rather than obscure.
8. A BIGWATER lake must be LAKE/POND type (SUBSET_ID =2 and FEAT_TYPE_ID <> 421 must be empty). Some exceptions are allowed for tidal flats (part of Sound), Reservoirs, and obscured dockland areas which are included in the BIGWATER representation.
9. BIGWATER features (both rivers and lakes) must not be too small. No features below a threshhold of Shape.area < 5000 are allowed, except dockland area polygons.
10. NULLs or no value values are not allowed in any item, except for the NAME item where blanks (no value) are allowed.
11. The maintenance database includes two addition items not included in the production warehouse database. The userid of the editor and the date edited are captured. This has been set to a publication default for this version but will be maintained for all future edits.
Only features that exhibited open water are included in this layer. However, to ensure completeness leeway was allowed to the editors to interpret the outer extent of the water body when broken by tree and shrub clusters or covered by surface-only vegetation.This may result in some inconsistency in how different water bodies are represented.
All features visible during the data development or quality assessment phases were captured, limited only by the ability to resolve at the capture scale. Small manmade features such as swimming pools, smaller landscape ponds, and other recreational water facilities were not included. Smaller features of interest may have been missed due to vegetation masking, or questions as to type of feature due to resolution of imagery. New features will be added and existing features corrected, based on user feedback and when the layer is reevaluated with 2007 imagery, when available.
The original coverage data in this layer was updated using the 2002 King County Natural Color orthoimagery. This imagery is considered to be the most spatially accurate of the four imagery sets used for this edition. Within the limits of the the visual resolution and editor digitizing, features with this source are accurate to plus/minus 2 feet. Where the 2002 USGS imagery was used (outside of the extent of the King County product), the accuracy is stated as 0.5 meter. There is no accuracy statement for the 2005 Aerials Express imagery, though where the same feature appeared in 2002 and 2005, the 2002 imagery location was chosen. The accuracy of the 2006 NAIP imagery is stated as current to FSA specifications. Due to its resolution and quality, this data was used only in cases where other data was not available to to define a feature was no longer present in 2006 or to create a new feature until it can be confirmed with more accurate 2007 data.
- Angel Lake renamed Angle Lake - Howard Hansen Reservoir was incorrectly labeled Chester Morse Lake. Corrected. - A small slough north of Mercer Slough Nature Park was edited so that the land between the two branches of the slough appears as non-water rather than an island.
Marine island polygons (those in Puget Sound, including Vashon), and Mercer Island polygon were permanently removed. The tide line in Puget Sound has been removed.
Prior to publication of user version to Spatial Data Warehouse the following geometry revisions are made programatically. 1. Freshwater islands are erased from underlying double-banked stream geometry 2. Manmade over-water features (Dams, wiers, docks, etc) are erased from the underlying waterbody.
Columns AA thru AN were completed at the start of the update. Three additional editors were assigned areas east of Column AN to assist in completing review of WTRBDY_AREA against the 2007 imagery. They worked on aerial waterbodies only, double-banked streams and edge-of-water (Puget Sound) are being handled separately.
The attributes provide required information for feature type determination, cartographic symbolization, provenance and topological associations.
Users should keep in mind two of the attributes, though based on ancillary data or comparative imagery analyses, contain subjective interpretations.
1. To assist users in a gross differentiation between 'natural' features and 'manmade features' areal waterbodies may be coded as FEAT_TYPE = Lake or Pond or as FEAT_TYPE = Residential or industrial water impoundments, respectively. This classication is not absolute and is based on a qualitative evaluation of the feature extent, boundary and appearance. However, any features seen in 2005/2006 imagery but not in early imagery are coded as impoundments. The FEAT_TYPE value assigned to individual features will be modified as necessary during maintenance cycles.
2. To assist users in making possible interpretations regarding wetland coincidence, the STATUS item is coded as POTENTIAL WETLAND where ancillary data provides this indication. The ancillary data includes the original coverage interpretation where the extent of the water body included non-water boundary areas and vector data compiled from many sources. Not all potential wetland areas are indicated and further refinement is anticipated.