Elevation Data Sources
Elevation GIS and CAD data comes in many forms, formats, and from many sources. The most accurate and useful elevation data for locations in North Carolina are LIDAR-based products discussed in the seperate section below.
LIDAR Based Elevation Data for North Carolina
Following Hurricane Floyd's flooding damage, North Carolina embarked on a joint effort with FEMA to re-map the state's flood zones. A by-product of this work is detailed elevation data collected by airborne LIDAR sensors. (NOTE: Raw pre-processed LIDAR data can be obtained from the USGS CLICK website for research needs.)
NCSU Libraries has a collection of DEMs by county for North Carolina.
- DEM resolution (cell size) is 20-foot with non-rounded/floating-point values.
- There is a zip file for each NC county, which contains an .asc file (ascii text file), .prj file, and .xml metadata file. The .asc files contain coordinates and elevation values for twenty-foot spaced points, and are converted to a raster based DEM using the "ASCII to Raster" GIS software conversion tool. Specify the "Output data type" as Float, in order to preserve the elevation decimal values.
- The difference between these files and what NC OneMap (via NCDOT) distributes (see below) is that the elevation values in this collection have NOT been rounded to the nearest foot. Instead, the floating point elevation values have been retained, which can be especially significant for applications in eastern NC.
- The coordinate system for these downloads is NC Stateplane, NAD 83, feet, and elevation values are in feet.
- The original statewide DEM is also available, named nc_20ft_grid.zip.
- Special thanks to Doug Newcomb with the U.S. Fish and Wildlife Service for providing the original statewide 20-ft. floating-point DEM.
Download Tip: To easily download many of the zip files at one time, try a Firefox extension such as DownloadThemAll! or use the ftp link with Internet Explorer and choose View -> "Open FTP Site in File Explorer."
For more information about the NC Floodplain Mapping Program (NCFMP), and full documentation on the LIDAR data collection process, see http://www.ncfloodmaps.com.
A LIDAR workshop was hosted by NCSU on August 4, 2004, and it's website has presentations and links to LIDAR data activity in NC that were relevant at that time.
Elevation Products at NC OneMap
A search for "elevation" on the NC OneMap Geospatial Portal gives sevearal potentially useful results, including contours, DEMs, hillshade, aspect (slope direction), and image services. Just be aware that the contours and DEMs produced by NC DOT have elevation values rounded to the nearest foot, so they may not be suitable for precision modeling.
NOAA Coastal Service Center, Digital Coast
LIDAR data is available for download for the Outer Banks and most of the US coastline from the NOAA Digital Coast website. These data were collected seperately than the statewide collection following Hurricane Floyd, and on multiple dates since the mid-90's through the present.
NCSU Campus Elevation Data
See the NCSU Campus GIS Data webpage for LIDAR data derivatives.
US, International Raster/Grid Sources
A valuable online (publically available) source of raster-based or grid elevation data for locations outside of North Carolina is the USGS National Map. It has the following elevation data products available at US and International extents:
- National Elevation Dataset (NED) - Regularly updated composite of the latest Digital Elevation Model (DEM) data for the US, and represents the most current and highest resolution DEM data available that USGS has produced. The entire United States has DEM coverage at 30 meter resolution (1 arc second, originally produced from topographic maps), and much of the country is available at 10 meter resoultion (1/3 arc second). For an expanded discussion, see the Libraries' DEM website.
- DEM Discovery Portal - Search by location for DEMs.
- Open Topography - Crowd-submitted sources for high-resolution topography data and tools.
- Global Digital Elevation Model (GDEM) - 99% global coverage, 30 meter resolution.
- Shuttle Radar Topography Mission (SRTM) - 80% global coverage, 30 and 90 meter resolution.
- ETOPO1 - 1 arc-minute (approx. 2 km) global relief model of the Earth, includes land topography and ocean bathymetry. Also two versions - an "ice surface" version has the Greenland and Antartic ice sheets, and a "Bedrock" version has the underlying terrain.
- GTOPO30 - Global Digital Elevation Model with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer).
The USGS also provides Web Map Service (WMS) links for Elevation data.
For NCSU affiliates, there are many elevation data sources including worldwide SRTM, GTOPO, and NED, on the Geodata Server, mostly from the ESRI Data and Maps collection. Click Here to execute a search for available data with the keyword "elevation."
Vector Contour Lines
Vector contour line data are often useful for visual or analytical purposes. Many local governments provide these data at varying contour intervals, for download from their websites. Go to NC local govt. GIS websites and check both the "Libraries' Archive" and "Download" links. In many cases, vector contour data is already on the Geodata Server. For example, to download contour data for a large area within the City of Raleigh from their tiled interface would take much longer than downloading this single geodatabase.
An alternative option for locations in North Carolina is to use NC DOT's contour data, discussed near the bottom of this webpage. For locations outside of NC, either search Google for locally maintained data, or contact Data Services to discuss your need.