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Layer: i07_Habitat_Delta_1977 (ID: 0)

Name: i07_Habitat_Delta_1977

Display Field: SYMBOL

Type: Feature Layer

Geometry Type: esriGeometryPolygon

Description: 1977 Delta Habitat Types were made digital by heads up digitizing registered scanned pages from 1979 Delta Environmental Atlas, produced by USACE. "The Habitat Types & Vegetation section delineates on 1 inch to 1000 foot scale aerial photographs the habitat types found in the Delta, described according to the classification system of the US Fish & Wildlife Service. Thirteen habitat types are defined in this Atlas. The system was based on a USFWS for its national wetland mapping program....The system was modified to include those terrestrial habitats, such as upland, agriculture, and urban, which were not included in the USFWS system. In addition, an open water classification was used in place of the USFWS river classification where the bottom type could not be identified." -excerpts from the 1979 USACE Delta Environmental Atlas, 7/1979. Digital images were clipped prior to warping to reduce risk of error during processing due to excess background. Digital clipped images were registered to USGS DOQQ's in ArcView 3.x(ESRI) utilizing Imagewarp 2.x extension. 23 October, 2002. Projection: UTM meters zone 10, nad 83. Accuracy within acceptable 7.5 Minute USGS map accuracy standards (1:24000 scale). For this set, the minimum number of control points used was 6 with an average of 8 to 9 points used. The pixel size for this set is 5.0 feet per pixel. User notes about the accuracy of this dataset (J Dudas, 1/24/2003): The goal of this project was to produce positionally accurate polygons which preserved the polygon areas/shapes as indicated in the Atlas plates. Chico State registered the scans to UTM Zone 10/NAD83, but it was clear that the scans had all sorts of distortions in them for a couple of fundamental reasons. The original Corps Atlas maps appear to have been produced by a fairly rough mosaicking, and as a result do not always correspond particularly well with DOQQs. Furthermore, the warping in the photos appears to get worse near the edges of the source photos, which suggests to me that the original photos were used in their entirety, rather than clipped, in effect a sidelap/overlap of 0%. As a result, the polygons were modified to reflect where some of these areas appeared in the 1993 DOQQs, for example, a channel island or a stretch of forest. In other words, the Corps Atlas polys were used to produce the shape geometry, and then the 1993 DOQQs provided the base for the actual poly locations. This will explain the positional offset seen between these polys and the scanned Atlas photos.

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