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Digital Aerial Imagery and Orthophotographs

Overview | Summary Table of Orthophoto Collections | Historic Aerial Photograph Collections



Overview

Aerial Image, true color, leaf-off

Digital aerial imagery and orthophotography are terms that refer to photographs taken usually from an airplane using either a film or digital camera. The photos are geometrically corrected, or "orthorectified," to adjust for topographic relief, as well as lens distortion and tilt from the camera position. The uniform scale of a digital orthophoto makes it possible to determine map measurements or to overlay information, using the digital orthophoto as a base map. Features are represented in their true ground position, making direct measurement of distance, areas, angles, and positions possible. The resulting images are usually mosaiced into a uniform tiling scheme. Thus for most collections, you must determine which tiles you need that cover your study area.

AlertPlease Note: Before downloading any imagery, ask yourself if you really need the imagery downloaded, or are you just using it as a background reference layer? If it's just for use in the background, it's much easier to stream the imagery from a WMS image server. Look for relevant WMS links in the table below.



Summary Table of Orthophoto Collections

The table below summarizes various available orthophoto collections.


Collection Name and LinksUsage Notes
North Carolina Regional and Statewide

In 2010, aerial photography for the entire state was caputured at 6 inch resolution color, leaf-off.

Beginning in 2012, imagery will be collected in one of four regions for the next four years, after which the cycle will begin again. Data collected in the Spring will be available in the Fall or Winter. More Info... (For a map of the regions and dates, see the "Business Plan").
  • Unless you have a specific need to download the imagery, it is recommend to simply view the imagery in a browser or GIS software using the WMS or Image Service links.
  • For downloading, if you select an area using the interactive map, you'll get an email with a link. The download is a zip file, containing your selected images as TIFFs.
  • This statewide initiative will provide the most current and highest resolution aerial data for NC available, with the exception of NAIP data (discussed below) depending on the location and the collection cycle.
  • Flights are conducted from February - April, in order to capture leaf-off conditions.
National Agriculture Imagery Program (NAIP)

See the Libraries' NAIP webpage for full details and access instructions.

  • Mostly statewide extent
  • 1-2 meter resolution; natural color and color-infrared (CIR)
  • Collected on a nearly annual basis (pending funding) since 2004.
  • Leaf-on (taken during the summer).
USGS National Map Seamless Server

The USGS National Map offers viewing, download, and WMS connection of multiresolution USGS orthophotography for dates and locations across the Unites States and its territories.

USGS EarthExplorer

The USGS EarthExplorer is a clearinghouse for a very large range of geospatial data types, including aerial photography, satellite imagery, and cartography products. Aerial photo products include: DOQ, NAPP, NHAP, and mosaics from various federal agencies.

This is a good place to find historic aerial images - some of which may be over 50 years old. See also the table for Historic Aerial Photos below.

  • Many image products at EarthExplorer are now free for download. Be sure to read message updates posted on their homepage for availability details.
  • You must allow pop-ups on EarthExplorer. Searching can be quirky. If you get an error, try a different web browser.
World Imagery

Search GIS Lookup for "imagery" to see catalog records of many other aerial and satellite-based imagery data sources in the Libraries' collection, including World imagery content.

  • ESRI provides an excellent selection of world imagery through ArcGIS.com which can be easily added or downloaded to ArcMap.
Online Imagery Sources

Geographic exploration software and online applications provide additional sources of aerial and orthophoto viewing:

  • These applications and websites are excellent for viewing data and information. However, they offer very limited analysis and export options.
  • These applications make heads-up digitizing of general landscape features fairly simple. Search online for data conversion tools, ie. KML to shape.
  • Extensive documentation and discussion exists elsewhere online for these services.
  • Much of Google and Microsoft's data are commercial, and certain uses may be restricted by licensing.


Historic Aerial Photograph Collections

Collection Name and LinksUsage Notes
County Collections

See the NC County GIS Data Directory for the following holdings and access links:

  • Use the "Libraries' Archive" links to see NCSU Libraries' holdings by year. You may need to contact Data Services for data access.
  • Use the "Web Map" links to view imagery on county mapping websites.
  • Use the "Data Download" links to download imagery files from county websites, if offered.

Also see webpages for Wake County, Raleigh, and NCSU Campus collections.

  • Usually the highest resolution available for any given time period. May or may not be the most current. Typically captured during the leaf-off season (late February through March).
  • Sources are from Counties directly, or from USGS thanks to cost-share funding, or from the NC Floodplain Mapping Program.
  • Dates, Resolution, tiling schemes, file formats, and other specifications vary widely.
  • Many images are in MrSID compressed format. Contact Data Services if you need uncompressed TIFFs.
  • The NC Geodetic Survey maintains a County Imagery Inventory (PDF) listing coordinators and currency dates.
Urban High-Resolution Orthophotography

USGS HRO website

See the Libraries' Urban High Res. Orthos webpage for full details and access instructions.

  • NC Coverage areas: Triangle, Triad, Charlotte metro, and other densely populated locations.
  • Dates of Acquisition: 2002 onward (see metadata for exact).
  • Resolution of 1/3 meter, or approx. 1 foot.
Digital Ortho Quarter-Quads (DOQQs)

See the Libraries' DOQQ webpage for full details and access instructions.

  • Two versions:
    1993 black/white, 1998 Color-infrared
  • Complete statewide extents
  • Produced and released by USGS
UNC's FSA images

UNC has digital scans of Farm Service Agency (FSA) aerial photo collections for the following Counties:

  • Wake (1938, 1959 and 1971)
  • Durham (1940, 1955 and 1972)
  • Orange (1938, 1955 and 1975)
  • Person (1955 and 1975)
Browse and Download from UNC

  • Image files are not presently georeferenced (do not have accompanying world files or coordinate information) for spatially positioning in GIS software, but it can be done by the end user.
USGS EarthExplorer

EarthExplorer has a wide range of aerial imagery spanning over 7 decades.

  • For more details, see the EarthExplorer record in the table above.
NC DOT Photogrametry Unit

The NC DOT Photogrametry Unit has a very large collection of aerial photo prints and negatives for North Carolina. These holdings are available to state agencies and the public.

  • Purposes are for highway planning. Flight paths are usually along highway corridors, either existing or planned, and are not organized in a typical county-wide grid or similar fashion.
  • More Information



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