2001 Digital Elevation Contours

In 2001, the North Central Texas Council of Governments facilitated the purchase of digital elevation contours for the following five counties in North Central Texas: Collin, Dallas, Denton, Rockwall and Tarrant. The contours were captured coincident with the 2001 digital aerial photography using light detection and ranging (LIDAR) and are available at two-foot intervals. The contractor for this project was Vargis, LLC.

Members of NCTCOG and private entities may purchase digital elevation contours at a cost of $25 per tile. Contours are sold as whole tiles only. Each tile is 3,000' x 2,000', or 0.215 square miles. Available file formats are ArcView shapefile (.shp), ArcInfo export (.e00), and AutoCad (.dxf). Sample files and a shapefile of the tile structure may be downloaded below; all orders for digital elevation contour products can be placed via www.dfwmaps.com. Before placing an order, read the instructions and frequently asked questions.

2-Foot Digital Elevation Contour Sample [Shapefile format]

2-Foot Digital Elevation Contour Sample [ArcInfo export format]

2-Foot Digital Elevation Contour Sample [AutoCAD dxf format]

LIDAR grid [README] - Shapefile, DXF file

Metadata for digital elevation contours [PDF]

Specifications

NCTCOG's contour products include digital elevation models (DEMs) and 2-foot contours. The terrain information used to generate the DEMs and contours was captured using an airborne Light Detection and Ranging (LIDAR) system. The collection and production conforms to the following specifications:

Sensor Type	Airborne LIDAR
Altitude of Capture	8,000' above mean terrain
Capture Period	November 2000-January 2001
Control Sources	Ground survey, airborne GPS and inertial measurement
DEM Point Spacing	3-5 meters (9.8-16.4 feet)
DEM Point Accuracy	15-20 cm (5.9-7.8") vertical on clearly defined ground features
Contour Interval	2 feet
Coordinate System	Texas State Plane, North Central Zone
Horizontal Datum	NAD 83
Vertical Datum	NAVD 88
Units	US Survey Feet
DEM Format	ASCII
Contour Format	ArcInfo

The LIDAR data were collected and processed under the supervision of Certified Photogrammetrists and Licensed Surveyors. The raw data were edited to remove above-ground features. The DEM and contours were interpolated from the LIDAR data and interactively edited to create a seamless and consistent coverage. Every fifth contour line is designated as an index and annotated. The contours are guaranteed to meet National Map Accuracy Standards at 2-foot intervals.

For questions about purchasing digital elevation contours, contact Shelley Broyles at 817-695-9156 or via email.