Contours 10 Foot Merge

Hypsography Digital Line Graph (DLG-3) data is currently derived
by digitizing the map features as line graph elements from the
cartographic source materials.  The scale of the source materials is
contained in the file header.  Most commonly, the scale is 1:24,000.
The scale is also reflected in the resolution field, which states the
ground length in meters of the smallest data collection unit (0.001
inch) for each scale (0.610 meters for 1:24,000 scale source data).
Large-scale Hypsography data files are derived primarily from USGS
 topographic maps published as 7.5-minute quadrangles at 1:24,000 or
1:25,000.  The Hypsography DLG-3 category consists of information on
topographic relief (primarily contour data) and supplementary spot
elevations.  The formal and abbreviated forms of this DLG category/
overlay are Hypsography and HP respectively.  All data structuring
standards (topology, elements, etc.), specifications (coordinate
systems, cell size, error definition), data quality (positional/
attribute accuracy, edge matching, edge alignment/status), and
distribution format information pertaining to the Hypsography DLG-3
is provided in the National Mapping Program Geospatial Standards
(Standards for Digital Line Graphs (Level 3)), Parts 1 - 3; 7/98
(see http://rmmcweb.cr.usgs.gov/public/nmpstds/dlgstds.html).  All
DLG-3 files submitted as final deliverables under this agreement
must be quality verified (per USGS DLG-3 standards) through the current
release of the PROSIX software.

This metadata document describes a Hypsography digital line graph
(DGL-3) file that is produced by AverStar Geospatial Services of
Portland, OR for the Texas Strategic Mapping Program (StratMAP).
StratMAP is administered by the Texas Water and Development Board
(TWDB) on behalf of the state of Texas (Texas Natural Resource
Information System (TNRIS)) for the purpose of creating digital line
graphs throughout the state.  StratMAP is supported by contributions
from the Federal Government, the State of Texas, and local and regional
organizations.  The DLG products produced for StratMAP and the Texas
Water and Development Board under the Texas StratMAP Program reside
in the public domain.  As described by USGS's Standards for Digital
Line Graphs, a digital line graph is a vector file of large-scale data
primarily from 1:24,000 scale USGS topographic quadrangles.  The basic
applications of DLG data are to support automation of cartographic
processes and automated spatial data analysis.  The DLG file structure
is designed to accommodate all categories of spatial data represented
on a conventional line map.  Node, line, and area types are accepted.
The attribute coding scheme is designed to accommodate several basic
cartographic data categories such as in this case, hypsography.  The
standard distribution format of these DLGs is DLG-3 optional format on
CD-ROM.  These have been converted from the original files produced in
standard USGS DCF format.

The DLG described in this document has been produced for use in a statewide base map series for the State of Texas.

REQUIRED: The state of the data set.
Data update frequency: REQUIRED: The frequency with which changes and additions are made to the data set after the initial data set is completed.

Who created the data: REQUIRED: The name of an organization or individual that developed the data set.

File name: contours_capcog
Type of data: vector digital data
Data processing environment: Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.5.1450

Contents last updated: 20080527 at time 09530100

Process description: Process_Step: Process_Description: Scanning - Calibration is performed on the Eagle Anatech 4080 black and white production scanner to optimize the results for the USGS film separates being scanned. A scan resolution of 800 dpi is used for all TWDB DLG separates. Pre-processing of quads is performed prior to actual production processing. In this manner, AverStar ensures that all scan files are of optimum quality for production. Batch processing is then performed on the scan files to prepare them for production use. Upon completion of the batch processing, a visual quality check is made on the batched maps. Each batched map is opened in the LT4X editing software and checked for presence of tics, content, and overall quality. Process_Date: unknown Process_Step: Process_Description: Registration - Next, the scanned maps are each geodetically registered. RMSE values are automatically calculated in LT4X and this value is checked to verify map registration accuracy. The RMSE is required to be within National Map Accuracy Standards. Process_Date: unknown Process_Step: Process_Description: First Edit - The first step within the editing phase is to update the DLG header items to accurately reflect information found on the source data. Vector editing is then performed utilizing pre- established menus containing approved LT4X processing macros for efficient production. Geodetic neatlines are generated in LT4X; these reflect the map units and projection. The vector data will then be more thoroughly cleaned in LT4X by stepping through the digital data on screen in a zoomed view mode. Once vector editing is complete, contours are then attributed with elevation values. Adjacent maps are closely reviewed during the attributing activity, as it is often very difficult to determine whether elevations are rising or falling near the neatline. Process_Date: unknown Process_Step: Process_Description: Spot Elevations - Once the Hypsography layer is complete through the first edit phase, corresponding spot, or point, elevations are then captured. Spot elevations are collected using a digitizing tablet. Published maps are registered to the tablet and spot elevations manually digitized. Once spot collection is complete, a series of topological checks is then performed to check the integrity of the map. A paper quality control plot of the spot elevations is created and a visual inspection of placement and accuracy performed. If errors are noticed in the spot inspection, they are corrected before completing the first edit. Process_Date: unknown Process_Step: Process_Description: Second Edit - The first edit soft copy and hard copy products are then reviewed within a controlled QA/QC process to ensure accuracy before finalizing data for edge matching and final PROSIX validation. Process_Date: unknown Process_Step: Process_Description: Edge Matching - Following the second edit step, all the adjacent edges are matched using LT4X. Adjacent map files are displayed in an on-screen view mode, checking each edge and manipulating lines to match in accordance with DLG product specifications. The USGS allows a six pixel movement for edge matching. Process_Date: unknown Process_Step: Process_Description: PROSIX - The PROSIX processing is used to ensure final verification and for structuring purposes. The PROSIX software structures the DLG into a DCF (Digital Cartographic File), which then in turn can be read by PROSIX and TRMPLT. PROSIX is also used verify the attributes of a single DCF, and to edgematch several DCFs before exporting as final DLGs. All edge QC flags will be properly set in the header prior to delivery. Process_Date: unknown Process_Step: Process_Description: Final QC / Header Check - Following the final PROSIX verification and edgematching, a final hard copy plot is produced and then compared to the published map. The plot is checked for completeness and accuracy. All final DLG products delivered will meet or exceed accuracy guidelines established by National Mapping Program Technical Instructions STANDARDS FOR DIGITAL LINE GRAPHS (4/96). Process_Date: unknown Process Description: When CAPCOG received the files, an attempt was made to find a common contour interval that could be used across the entire CAPCOG region. The 10 foot interval was deemed adequate, an a process was implemented to merge the files while cleaning up the dataset topology.
Source used: C:\GIS\Projects2006\contours\CAPCOG_contours

Horizontal_Positional_Accuracy_Report:
        The DLG positional error shall be less than or equal to 0.003 inches
        standard error in both x and y component directions.  The data is
        collected and processed using equipment with a resolution of 0.001 inch.
        The positional accuracy of the data and completeness of the file are
        checked by visually comparing proof plots with the source materials.
        As set by the National Map Accuracy Standards, an acceptable
        registration RMSE must be below 20 ground feet for a 1:24,000 scale map.
      Quantitative_Horizontal_Positional_Accuracy_Assessment:
        Horizontal_Positional_Accuracy_Value: 40
        Horizontal_Positional_Accuracy_Explanation:
          DLG positional accuracy is based on the use of standard USGS graphic
          products as the fundamental source for initial loading of the NDCDB.
          These sourcegraphics are normally compiled to meet National Map
          Accuracy Standards, where 90% of well-defined features are to be
          within 0.02 inches of true mapped ground position (40 feet for
          1:24,000 scale source maps).  U.S. Bureau of the Budget, 1947, United
          States National Map Accuracy Standard.

ESRI feature type: Simple
Geometry type: Polyline
Topology: FALSE
Feature count: 170386
Spatial Index: TRUE
Linear referencing: FALSE