This page attempts to answer common questions that people may have about the NC OneMap Statewide Orthoimagery 2010 project. If you have a question that happens to not be answered on this page please send an email with additional questions or comments to CGIA. The following questions and answers are organized in five sections: (1) Orthoimagery Products, (2) Imagery Acquisition and Sharing, (3) What the Project Means for Counties, (4) Using the Orthoimagery Products, and (5) This Year.
A summary of the data deliverables and the approximate file size for counties are available in a summary document.
1.1 What imagery products will the project deliver to the counties?
The products will be statewide digital orthoimagery at a ground resolution of 0.5 feet (6-inch pixels, equivalent to 1 inch = 200 scale mapping), true color, in uncompressed (GeoTIFF) and compressed (MrSID, 20 to 1 ratio by tile and MrSID, 50 to 1 county mosaic) formats, validated metadata (Federal Geographic Data Committee standard), and a tile index (shapefile) for the 5,000 by 5,000 foot tiles. Compressed tiles and county mosaics will be included for all neighboring counties on the portable drive delivered to each county. Imagery in compressed format will be available for free download through NC OneMap.
1.1bWhen will imagery products be delivered to counties?
The delivery of orthoimagery datasets to counties will occur by April 30, 2011. The statewide scope of the project, high resolution of the imagery, processing in large multi-county blocks, and extensive visual and positional quality control all take months to complete before data will be finally packaged by county and approved for distribution. Until products are approved for distribution, a specific delivery schedule by county cannot be predicted.
1.2 Will the new orthoimagery products include large water bodies such as the Pamlico Sound?
The flights will not acquire new imagery over the sounds or ocean beyond at least 2,000 feet from the apparent shoreline represented in the statewide county boundary dataset published by NC DOT. However, to meet search and rescue operations and for map design purposes, the project will integrate available satellite or aerial images of water to represent large water surface in final ortho products. Therefore, the products will not have gaps over the water bodies.
1.4 Will color infrared imagery be included?
No. The images will be true color only for this project (using the red, green and blue bands collected by the sensors). However, the digital cameras will collect and store an unprocessed fourth band (infrared). Processing the fourth band into ortho imagery represents a significant technical effort and expense. For somewhere on the order of 10 to 12 percent on top of the delivered cost of the true color product, a contractor could process a second set of imagery using the fourth band. The potential benefit from color infrared imagery relating to forest assessment, fire prevention, impervious surface and other ground features could be realized after this project in selected locations, supported by separate funding sources. For a fact sheet and information on how to obtain the semi processed or raw data, see Acquisition of Color Infrared Aerial Imagery Data on the NC Orthos overview page at NC OneMap.
1.6 Will elevation datasets be delivered to counties on the portable drives?
No. Elevation used in the processing of ortho imagery will be based on digital elevation models derived from Light Detection and Radar (LIDAR) bare earth data managed by the NC Floodplain Mapping Program. Orthoimagery contractors may modify the digital elevation models if terrain has changed significantly. The current and modified elevation datasets will be available for download from http://www.ncfloodmaps.com.
1.7 Will this project provide oblique imagery?
No. The deliverables will be statewide ortho imagery that will be made available to all counties and the public at no charge. This product meets the state specifications and is best suited for representing ground locations and ground features including street centerlines, property boundaries, streams and other base mapping features. This approach best serves the purpose of statewide, consistent, current imagery that can be widely shared.
2.1 What technical specifications will be used for the orthoimagery?
The imagery will be created and delivered consistent with the new state standards (signed by the Secretary of State on October 1, 2009). See North Carolina Technical Specifications for Digital Orthophoto Base Mapping, Land Records Management Division, North Carolina Department of the Secretary of State, Edited by Thomas W. Morgan, August 20, 2009. See http://www.secretary.state.nc.us/land/
2.4 Will the orthoimagery be delivered after all counties are complete or county by county as soon as it is processed?
Data will be delivered after approval by the NC 911 Board. This project has many steps in aerial image acquisition, processing, and quality control. There will be four regions, multiple contractors, processes to resolve any differences in images at regional boundaries, and quality control for positional accuracy and visual quality. Project status is updated weekly and displayed on the project website at nconemap.gov. Data for neighboring counties will be included in the products for each county. Until the final products are approved for distribution, a specific delivery schedule by county cannot be predicted.
2.5 Will each county be involved in a contracting process with orthoimagery service providers?
No. The City of Durham will contract with CGIA to manage the orthoimagery project. CGIA will enter into an agreement with the NC Floodplain Mapping Program to manage the data development. The NC Floodplain Mapping Program will task its contractors from an existing Qualifications-Based Selection (QBS) contract to acquire the orthoimagery, and also use an existing contract with the NC Geodetic Survey for system upgrades and management of a new Qualifications-Based Selection of contractors for horizontal quality control.
2.6 Will the City of Durham select the contractors and manage the project?
No. Contracts and the project will be managed by CGIA in collaboration with Durham, the 911 Board, NC Floodplain Mapping Program, NC Geodetic Survey, and the Land Records Management Division in the Secretary of State’s Office. The Working Group for Orthophotography Planning under the Statewide Mapping Advisory Committee of the NC Geographic Information Coordinating Council will serve as a technical advisory group for the project.
2.9 Will the orthoimagery be readily accessible to the public? If yes, in what format(s) and how?
Ortho imagery, in compressed format (MrSID), will be downloadable by any Internet user from NC OneMap (www.nconemap.com) in a similar approach to the current file transfer routine (FTP). The project team will share copies of the imagery (via portable disk drives and other available methods) with the intention that state and federal agencies obtain copies from the project (not from individual counties). CGIA is assessing additional ways to make the imagery products readily available online.
5.1 Why did the City of Durham apply for a grant to fly statewide imagery?
The North Carolina 911 Board initiated a grant process for Public Safety Answering Points (PSAP) to support local needs. The City of Durham Emergency Communications Center recognized that the value of up-to-date, consistent imagery would apply equally to E-911 operations in its neighboring counties. The Durham PSAP met with the state’s Working Group for Orthophotography Planning to discuss statewide issues related to ortho imagery. The current situation is a patchwork of imagery (years captured) and a slower pace of new imagery acquisition that will not meet the goal of imagery no more than four years old in all counties. Considering the aging ortho imagery in many of the rural counties and widespread local budget problems, Durham PSAP concluded that a statewide project would maximize benefits in a timely way.
5.3 Why Didn’t the State Tell Counties Who Were Planning to Fly in 2009 to Wait a Year?
In 2008, when counties were planning projects that would produce ortho imagery from 2009 flights, the Statewide Mapping Advisory Committee and the Working Group for Orthophotography Planning knew nothing about the possibility of a future grant process relating to the 911 Board and Public Safety Answering Points. The Working Group learned of the opportunity in May 2009 when the City of Durham was drafting its grant proposal.
5.4 How does this project relate to the GICC’s Statement of Direction for High Resolution Digital Aerial Imagery (August 20, 2003)
This project is consistent with the intent of the Statement of Direction: “Aerial imagery developed as part of the program will be consistent with the needs of local government and meet specifications of the North Carolina Land Records Management Program, the North Carolina Geodetic Survey, and the Statewide Mapping Advisory Committee (SMAC)… The program will be consistent with the goals, characteristics, and implementation plans of NC OneMap… (until a robust state program for funding orthoimagery is established) the Council directs the SMAC to exploit every appropriate short term opportunity to share costs, negotiate in-kind services or seek other resources of member organizations, federal partners, and others for joint development of high resolution aerial imagery with local governments.”
If you have a question that happens to not be answered on this page please send an email with additional questions or comments to CGIA.