This data layer was compiled from 1:100,000 scale DLG hypsography data in order to create topographic contour lines suitable to use as part of a digital base map for the Quaternary Geologic Map of Connecticut and Long Island Sound Basin, USGS I-2784, Stone and others, in press. The vectors (20 meter intervals) were edgematched, edited, and attributed for the purpose of developing a topographic base for the Quaternary Map, but may be useful with other maps of similar scale (1:125,000).
Created as part of the publication process for the Quaternary Geologic Map of Connecticut and Long Island Sound Basin (USGS I-2784), in order to provide a topographic base for the display of geologic units. This layer may provide useful topographic information for other data layers and maps of similar scale (1:125,000).
The Long Island Sound Resource Center is a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut
publication date
None. No restrictions or legal prerequisites for using the data after access is granted. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:100,000 scale (1 inch = 1.578 mile). Although this data set has been used by the Long Island Sound Resource Center and the U.S Geological Survey, no warranty, expressed or implied, is made by the Long Island Sound Resource Center and the U.S Geological Survey as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the Long Island Sound Resource Center or the U.S Geological Survey in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing this data on a map or using it in a software application, analysis, or report, please acknowledge the Long Island Sound Resource Center and the U.S Geological Survey as the source for this information. For example, include the following data source description when printing this layer on a map: Elevation Contours - From the Connecticut 20 Meter Hypsography layer, compiled and published by the LISRC and USGS. Source map scale is 1:100,000.
Long Island Sound Resource Center
UConn Avery Point
1080 Shennecossett Rd
Mary DiGiacomo-Cohen (Long Island Sound Resource Center) for compiling and editing the data; Russell A. Ambroziak (USGS Mapping Division) for assistance in providing the source data.
Editing and edgematching was completed for the purpose of creating topographic contours for use as a 1:125,000 scale base map. The numerous errors and inconsistencies in the source material was most obvious at the boundaries of the sections and these areas received the most effort during editing and edgematching; although the entire data layer has been visually checked, errors may still exist particularly in the central areas of each original 100k sheet section. Line features conform to the following topological rules. Lines are single part. There are no duplicate lines. Lines do not self overlap. Lines do not overlap other lines. Lines intersect only at nodes, and nodes anchor the ends of all lines. Lines do not overshoot or undershoot other lines they are supposed to meet and intersect.
Complete for the state of Connecticut.
The horizontal positional accuracy of this data is no better than the United States National Map Accuracy Standards for 1:100,000 scale maps. According to this standard, not more than 10 percent of the locations tested are to be in error by more than 1/50 inch (167 feet) measured on the publication scale of a 1:100,000-scale metic topographic-bathymetric map produced by the U.S. Geological Survey.
ungenerated vectors and attribute information in ASCII format
CT20MHYP is in Shapefile format.
Includes all line features from the CT20MHYP ArcInfo Coverage. Hypsography_20_Meter.shp is in Shapefile format.
Includes all line features from the Hypsography_20_Meter.shp Shapefile. Hypsography_20_Meter is in GeoDatabase Feature Class format.
Primitive format DLG-source data (.ltx, .lfa, .un, and .def files, which are ASCII format, similar to ungenerate arc coverages and comma separated data from info tables, in CT state plane NAD 27) was generate into 9 Arc coverages using the Prim2arc.aml program (Jim Reddy, USGS). This includes Arc commands: generate, joinitem, and build).
Long Island Sound Resource Center
The border sections were clipped to the state boundary. The 20m contours from all sections were edgematched along boundaries and edited where necessary (using the 24,000 scale quad DRGs as backdrop and edited to approximate that geometry and elevation where there were obvious errors). Note - the western most sections had only 20m interval data, so although the majority of the state had 10m interval data, the odd 10 m interval contours (10, 30, 50, etc) were deleted to create a consistent layer. Supplmental, non-matching attribute items were deleted and the sections were appended. Attributes 'index' and 'label' were added and populated for the purpose of creating a graphic layer suitable for the quaternary map. Coverage projected to NAD83
Long Island Sound Resource Center
UConn Avery Point
1080 Shennecossett Rd
Converted the data from ArcInfo Coverage to Shapefile format and named the shapefile Hypsography_20_Meter.shp. Deleted the FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH, CT20MHYP#, CT20MHYP-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with data that is in ArcInfo Coverage format. Also renamed the ELEV__M01, INDEX, and LABEL fields in the ArcInfo Coverage to ELEV_M, INDEX_FLG, and LABEL_FLG. For the INDEX_FLG and LABEL_FLG, converted attribute values from 'y' or 'blank' to 'Y' or 'N' the information more intuitive to user. Deleted the ELEV_MO2 attribute because metadata indicated not to use the field.
79 Elm Street
Convert to GeoDatabase Feature Class format - Defined new Feature Class named Hypsography_20_Meter; and imported the attribute definitions, loaded features and imported metadata from Hypsography_20_Meter.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
79 Elm Street
Internal feature number.
ESRI
Feature geometry.
ESRI
Feature Identification
compiler and editor
Feature Description
compiler and editor
Contour Interval in Meters
compiler and editor
Label Flag
editor
yes, this contour should be labeled
editor
no, contour should not be labeled
editor
Feature geometry.
ESRI
Index Contour Flag - Identifies contours every 100 meters.
editor
yes this is an index contour (100 m interval) to highlight on a map
editor
20 meter contour
editor
Lines and their attributes have edited, edgematched, and sometimes simpilfied from DLG source data (for example carrying contours will no longer contain all elevations as items elev__m03, elev__m04 have dropped during append). Items index and label have been added for the purpose of creating graphic fiels for the production a base map for the CT Quaternary Map. "Index" flags 100 m contours and "label" flags semi-randomly chosen lines for labeling purposes.
USGS 1:100,000 scale DLG hypsography data
79 Elm Street
Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata.
The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.
Long Island Sound Resource Center
UConn Avery Point
1080 Shennecossett Rd