Carquinez Strait Maps -- Small Scale - Vector Features
Scroll down for a description of the data used in this map, or click anywhere on the map to download an 8.5" x 11" scaled PDF.
This 1:55,000 scale map represents the mapped extent of the project and shows all of the vector features created in this project.
Contour Lines
The contour lines were generated with ESRI's 3D Analyst at ten meter intervals based on 1/3 arc-second DEMs from the USGS seamless server. The output contour line table was then processed with the field calculator using the following VB expression:
Abs (([Contour] / 50 - INT([Contour] / 50 )) * 10 = 0)
This VB expression adds a field to the contour table to hold the result of the field calculator expression. The general form of the statement is:
Abs (([Contour] / X - INT([Contour] / X )) * 10 = 0)
where X is the product of the contour interval and how many contour lines one wants between labeled (boss) contour lines (n). The result is either a 0 or 1 with a 1 representing every nth contour line.
After the new field was populated the symbology tab was used to create a new label class via an SQL query where the new label class contained the records where the new field was equal to 1. At this point one can individually label this class with the Contour field from the contour analysis to visually have contour lines with labels denoting elevation every nth contour line.
This process yielded a label class that represents every five contour lines given a ten meter contour interval. This label class was given a different symbology from the intermediate contour lines resulting in every fifth contour line being bolder and labeled with elevation.*
Roads
The roads shown were selected for spatial reference given the map's parks, trails, and points of interest features. The roads were heads-up digitized using one-meter NAIP color orthos and are stored in a file-based geodatabase feature dataset with feature classes being used to delineate between road types such as divided roads, county roads, and municipal roads.
Water Features
The Carquinez Strait shoreline was heads-up digitized from a USGS DRG last updated in 1980. This source was chosen over the NAIP ortho photography primarily due to the fact that the orthos were acquired during low tide and that USGS 7.5 quad maps show mean water levels.
Lake Herman was also heads-up digitized from the 1980 USGS DRG due to the fact that it is the City of Benicia's water reservoir, and because of this the water level fluctuates by large amounts over time.
Park Boundaries, Trails, and Points of Interest
Two hundred forty-four GPS waypoints were acquired to serve as point coordinates in defining three classes of data: Points of Interest (point feature class), Trails (line feature class), and Boundaries (polygon feature class). The waypoints were collected over a two month period in relatively small batches and compiled in an Excel file with added attributes so as to enable class extraction.
The Excel file was imported into the project's file-based geodatabase as a feature dataset with feature classes being extracted based on attributes so as to arrive at polygon classes (park boundaries), line classes (walking trails), and point classes (points of interest.)
Annotation
The annotation is stored as georeferenced symbology in the same file-based database that the base maps, vector files, and elevation data are stored in. The geodatabase dataset for the annotation contains five data classes: Land Area, Transportation, Land Features, Municipalities, and Water Features.
Each annotation class was defined with a default font, font size, effects (bold, italic, halo, etc.) and modified per instance when needed.
* Method provided by Steve Nakazono, M.A., GIS Analyst - Chevron Energy.