Internal feature number.

ESRI

Feature geometry.

ESRI

Railroad Arc Code. Numeric values that identify railroad feature types.

State of Connecticut, Department of Environmental Protection

Railroad Class. Text values that correspond to the numeric RRARC_COD attribute values. RAIL_CLASS is the English language equivalent of (decodes) the RRARC_COD field.

State of Connecticut, Department of Environmental Protection

ArcView Legend. Text field for symbolizing railroad feature types on a map.

State of Connecticut, Department of Environmental Protection

Internet Mapping Software Legend. Text field for symbolizing railroad feature types on an Internet map.

State of Connecticut, Department of Environmental Protection

USGS Large Scale Digital Line Graph (DLG) data are digital representations of the cartographic (base map) information published on the 1:24,000-scale, 7.5 minute topographic quadrangle maps. The USGS produces DLG data per 7.5 minute quadrangle. DLG data is organized into categories such as hydrography, boundaries, and transportation. At the time the State of Connecticut began developing the Railroads layer in the late 1980's, Large Scale DLG files were available for 112 of the 115 topographic quadrangle maps necessary to cover Connecticut. Large Scale DLG files were not available for the West Springfield Mass-Conn, Springfield South Mass-Conn, and Hamden Mass-Conn quadrangle. It is important to note that the Large-Scale DLGs were produced in the 1980's at a time when the USGS was developing standards, conventions, and procedures to convert topographic quadrangle maps into digital spatial data. The Connecticut DLG files were produced by digitizing from stable-base mylars using a digitizing tablet to capture the digital data. The features were manually digitized and attributed. Today, there are other methods available for producing DLGs. For additional DLG documentation, refer to the Data User Guides and Standards for 1:24,000-Scale Digital Line Graphs and Quadrangle Maps available from the U.S. Geological Survey, National Mapping Program.

Publication dates of the USGS 7.5 minute topographic quadrangle maps for the State of Connecticut through 1984.

In the absence of Large Scale DLG data, the USGS provided the State of Connecticut with raster image scans of the mylar separates used to publish the black, red, brown, and blue inks for 3 of the 115 topographic quadrangle maps that cover Connecticut. These quadrangles include West Springfield Mass-Conn, Springfield South Mass-Conn, and Hamden Mass-Conn.

publication date

Railroad features for each quadrangle map.

Publication dates of the USGS 7.5 minute topographic quadrangle maps for the State of Connecticut through 1984.

Railroad features for Connecticut combined in a single, statewide layer. Railroad is in ArcInfo Coverage format.

Publication dates of the USGS 7.5 minute topographic quadrangle maps for the State of Connecticut through 1984.

Railroad features for Connecticut combined in a single, statewide layer. Railroad.shp is in Shapefile format.

Publication dates of the USGS 7.5 minute topographic quadrangle maps for the State of Connecticut through 1984.

Railroad features for Connecticut combined in a single, statewide layer. Railroad is in GeoDatabase Feature Class format.

Publication dates of the USGS 7.5 minute topographic quadrangle maps for the State of Connecticut through 1984.

DLG to ArcInfo coverage format conversion - Using ESRI ArcInfo software, the State of Connecticut, Department of Enviromental Protection converted the Railroad overlay from the Transporation category for each Large Scale DLG file to ArcInfo Coverage format, resulting in one ArcInfo Coverage of linear features for each quadrangle area. The Transportation category of data includes major transportation systems collected in three separate overlays labeled: (1) Roads and Trails, (2) Railroads, and (3) Pipelines, Transmission Lines, and Miscellaneous Transportation Features. Only the Railroad overlay was extracted from the Transportation Layer as a data source for this layer. Each Coverage was converted from UTM to Connecticut State Plane, North American Datum of 1927 (NAD27).

Image to vector (ArcInfo coverage) format conversion - Using ESRI ArcInfo software, the black ink image files that depict the railroad (and road and trail features) on three topographic quadrangle maps were georeferenced to Connecticut State Plane, North American Datum of 1927 (NAD27) by registering the image corners to the corresponding quadrangle corner tics.  In an interactive ArcInfo editing environment, the railroad track features were visually identified on the background image and manually vectorized. Railroad features that would have been included in the DLG Transportation category by the USGS were were manually digitized on the screen (heads-up digitizing). Features were assigned RRARC_COD values based on their cartographic representation on the topographic quadrangle maps. Check plots were made to inspect digitizing quality and the assignment of RRARC_COD values.

Attribute value verification - The quality and accuracy of the digitizing and coding of the railroad features was checked by comparing the transporation features in each ArcInfo Coverage with the railroad features on the published USGS topographic quadrangle maps. Visual comparisons using 1:24,000 scale paper check plots combined with automated procedures to identify inconsistent attribute coding were the primary means of evaluating and correcting obvious errors with the original DLG data. Where necessary, corrections were made to DLG major and minor codes in the ArcInfo Coverages. The original DLG major and minor codes were modified to form the RRARC_COD attribute in the final Railroads layer.

Quadrangle coverage edgematch - Using ESRI ArcInfo software, the individual 7.5 minute quadrangle coverages of Railroad features were systematically edgematched. Features along the edges of adjacent quadrangle were moved to make their end-point coordinates identical through a process of checkerboard style edgematching. Features on every other quadrangle were adjusted. The ends of Railroad segments were snapped to align with the connecting stationary features on adjacent quadrangles if their end-points were generally within 20 feet. On occasion, there were no connecting features on adjacent quadrangles to match to so some features abruptly end at quadrangle boundaries. This is mostly due to variations in quadrangle publication dates.  Varying publication dates also explain inconsistent DLG major and minor codes for certain railroads that appear on more than one topographic map. For example, a track that appears on two adjacent quadrangle maps may appear as a track on one map and abandoned track on the adjacent (more recent) map. Consequently, RRARC_COD values for some railroad tracks change when crossing quadrangle boundaries. These inconsistencies were not resolved because the intent was to represent the classification of these features on USGS topographic quadrangle maps.

Statewide layer creation - Using ESRI ArcInfo sofware, all of individual 7.5 minute quadrangle coverages were appended to form a single, statewide Railroads layer.  Linear features were unsplit (merged) to eliminate unnecessary pseudo nodes between similar features from adjacent quadrangle areas. Final line feature topology was established with ArcInfo Fuzzy and Dangle tolerances verified at 4 and 10 feet, respectively. At this step in the process the Railroads layer was fully attributed and ready for use. Not all data fields from the orginal DLG files were preserved by this step in the process. A new data field, AV_LEGEND, was added to more easily classify and cartographically represent features when displaying the information with software such as ArcView.

Datum conversion - Using ESRI ArcInfo software, the Railroads layer was converted from the Connecticut State Plane Coordinate System of 1927 (NAD27) to the Connecticut State Plane Coordinate System of 1983 (NAD83). The NADCON (North American Datum CONversion) data transformation was used.

Attribute enhancements - RAIL_CLASS and AV_LEGEND attributes were changed from storing abbreviated values in upper case (e.g. TRACK, SIDING, STATION ) to full length values in both upper and lower case (e.g. Track, Siding, Station). Additionally the IMS_LEGEND attribute was added to establish a very general classification scheme for symbolizing railroad features with Internet mapping software environments such as ArcIMS. The following attributes from the original DLG files were removed from the data table due to poor data quality: PHOTRV_FLG and QUAD_NO. These attribute values were inconsistent, not verified and of limited value to the State of Connecticut. Using Arc Macro Language (AML), an automated process (MAKECOVER.AML) was developed to maintain consistent attribute values by programmatically joining lookup data tables to decode numeric code fields.  The MAKECOVER.AML also created this particular copy of the Railroads layer that is clipped to the State of Connecticut boundary.

Create 2005 Edition of Railroad - The automated process (software program), MAKECOVER.AML, developed for the previous process step was executed in 2005 in order to create a 2005 edition (copy) of Railroad that captures recent corrections and enhancements made to the layer. The MAKECOVER.AML program was last run in 2005, and the name of the resulting ArcInfo coverage created by this automated process is RAIL. Note, this particular run of the MAKECOVER.AML created a copy of the Railroad ArcInfo coverage that is clipped to the State of Connecticut boundary and is named RAIL instead of RAILMASTER. Prior to 2005, the Railroads layer in ArcInfo Coverage format that was clipped to the state of Connecticut boundary was named RAILROADCT.

Export to Shapefile format - Converted line feature data from an ArcInfo coverage named RAIL to a Shapefile named Railroad.shp. Excluded the FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH, RAIL#, RAIL-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with spatial data that is ArcInfo coverage format.

Convert to GeoDatabase Feature Class format - Defined new Feature Class named Railroad; and imported the attribute definitions, loaded features and imported metadata from Railroad.shp shapefile. 

Spatial Reference Properties for Feature Class:

Coordinate System: NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet
XY Domain MinX: 100000; MaxX: 2247483.645
XY Domain MinY: 200000; MaxY: 2347483.645
Precision: 1000