The District of Columbia

USGS High Resolution State Orthoimagery for the District of Columbia: 2012

USGS High Resolution State Orthoimagery for the District of Columbia: 2012

by U.S. Geological Survey on 2012

Keywords
About: digital spatial data, 0.3 meter orthoimage, rectified image, orthophoto, natural color orthophoto, orthoimage, image map, imageryBaseMapsEarthCover, 010, National Standards for Spatial Digital Accuracy (NSSDA)
Taking place at: United States, U.S., US, Washington, Maryland, Virginia, City of Washington D.C., Distric of Columbia

Abstract

"This data set consists of 0.3-meter pixel resolution (approximately 1-foot), natural color orthoimages covering the urban area footprint. An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. The design accuracy is estimated not to exceed 1.52-meters NSSDA 95% confidence (0.88-meters Root Mean Squared (RMSE) Error XY (0.62 meter RMSE X or Y). Each orthoimage provides imagery over a 1500-meter by 1500-meter block on the ground. There is no image overlap between adjacent files. The projected coordinate system is UTM Zone 18N with a NAD83 (NSRS2007) datum. The naming convention is based on the U. S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage."
An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. There is no image overlap between adjacent files.

Data received at EROS were verified as:
Projection: NAD_1983_UTM_Zone_18N
Resolution: 0.3000 m
Type: Natural Color

and resampled to align to the USNG using the USGS Seamless system system. The naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage. The naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage. The metadata were imported and updated for display through The USGS Seamless system Server at Chip-level metadata are provided in HTML and XML format.

Purpose

"This data depicts geographic features on the surface of the earth. It was created to provide easily accessible geospatial data which is readily available to enhance the capability of Federal, State, and local emergency responders, as well as plan for homeland security efforts. This data also supports The National Map."
A digital orthoimage is a geometrically accurate photographic record of landscape conditions at the time of the corresponding aerial photography. As such, High Resolution Orthoimagery is useful for a variety of applications, such as environmental monitoring, facility engineering/maintenance, city/county planning, property line review, etc. The digital orthoimage can be used alone or as a raster basemap for corresponding vector line mapping. The detailed focus of High Resolution Orthoimagery provides emergency responders critical information in determining the best evacuation routes, alternative routes and safe access to aid. High Resolution Orthoimagery assists law enforcement personnel in determining the best locations to place surveillance cameras in high-traffic urban areas and popular attractions. The data assists Federal, State and local emergency responders in planning for homeland security efforts. This data also supports The USGS Seamless system.

Access constraints

Any downloading and use of these data signifies a user's agreement to comprehension and compliance of the USGS Standard Disclaimer. Insure all portions of metadata are read and clearly understood before using these data in order to protect both user and USGS interests.

Use constraints

" None. However, users should be aware that temporal changes may have occurred since this data set was collected and that some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of it's limitations. Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data."
There is no guarantee of warranty concerning the accuracy of the data. Users should be aware that temporal changes may have occurred since this data set was collected and that some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Acknowledgement of the originating agencies would be appreciated in products derived from these data. Any user who modifies the data is obligated to describe the types of modifications they perform. User specifically agrees not to misrepresent the data, nor to imply that changes made were approved or endorsed by the U.S. Geological Survey. Please refer to http://www.usgs.gov/privacy.html for the USGS disclaimer.

Point of contact


in U.S. Geological Survey

USGS Earth Resources Observation and Science Center
Sioux Falls SD, 57198-0001, USA

phone: 605.594.6151
fax: 605.594.6589
hours: 0800 - 1600 CT, M - F (-6h CST/-5h CDT GMT)

Credits

U.S. Geological Survey and Fugro EarthData, Inc.

Data accuracy

Accuracy
Radiometry is verified by visual inspection of the digital orthophoto. Slight systematic radiometric differences may exist between adjacent orthoimage files; these are due primarily to differences in source image capture dates and sun angles along flight lines. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent orthoimage file coverages. Tonal balancing may be performed over a group of images during the mosaicking process which may serve to lighten or darken adjacent images for better color tone matching.

Logical consistency
"All GeoTIFF tagged data and image file sizes are validated using commercial GIS software to ensure proper loading before being archived. This validation procedure ensures correct physical format and field values for tagged elements. Seamlines and tile edges are visually inspected. Seamline mismatches are not corrected unless the overall displacement exceeds 0.6 meters."
Logical consistency is implicit in the raster image data structure. Source imagery is cloud free.

Completeness
"Orthoimages are visually inspected for completeness to ensure that no gaps or image misplacements exist within and between adjacent images. These images are derived by mosaicking multiple images to ensure complete coverage. Source imagery is cloud free."

Horizontal positional accuracy
"The orthophotos were created to be fully compliant with a horizontal positional accuracy shall not exceed 1.52 meter tested to NSSDA Standards (95% confidence)."
The relative accuracy is assembled by comparing rectified images generated from adjacent strips of imagery. The absolute accuracy is assessed by measuring the ground control points in the rectified image against the actual surveyed co-ordinate position. The testing is for overall accuracy. This data has been produced to be fully compliant with the National Map Accuracy Standards (NMAS) for mapping at this scale.

Vertical positional accuracy
There is no vertical accuracy component to orthophotography.

Lineage / Sources

  • District of Columbia Raw ADS80 imagery
    on-line, raw red, green, and blue wavelengths collected at 2,880 meters above mean terrain. This is the input data for the digital orthophotos.
    wavelengths bands
    by Fugro EarthData, Inc., 20120607
  • ground survey
    spreadsheet, Ground control survey to support photogrammetric mapping and blind QC points.
    ground control
    by TerraSurv, Inc., 20120404
  • Pixel Factory DEM
    network drives, Autocorrelated surface generated to support the development of orthophotography. The surface is edited into a bare earth DEM for use in orthorectification.
    surface
    by Fugro EarthData, Inc., 20120625
Lineage / Processes
"The digital orthophotography is comprised of a 24 bit, natural color RGB bands, 30cm pixel resolution ground orthos covering the District of Columbia project area. The imagery was acquired on April 3 and June 7, 2012. The Pixel Factory process was used in the generation of the orthoimagery covering all project tiles. The initial radiometric adjustments were performed on the imagery for each flight line attempting to reach the best possible histogram. The rectification process was then run using the processed DSM and the radiometrically balanced imagery on each flight line. The quicklook (reduced resolution rectification) of each flight line exported out of Pixel Factory. A second set of radiometric adjustments were made using Fugro proprietary tools. The radiometrically balanced imagery was then re-imported into the Pixel Factory system and the histogram from the quicklook was applied to the full resolution imagery. Mosaic lines were placed, joining the ADS80 imagery strips. An initial QA/QC was performed by the technician to ensure that the mosaic lines were appropriately placed and that there was appropriate imagery coverage. The final imagery data set is removed from the Pixel Factory environment in a process called "packaging" where the individual tiles are created. All data processing in the Pixel Factory system is performed in UTM Zone 18N meters; it is during packaging that final datum and projection are defined. The created tiles are reviewed again for anomalies and interactive radiometric adjustment applied where needed. QA/QC was performed looking for anomalies, smears and other indications of problems within the digital orthophoto creation process, interactive radiometric adjustment applied where needed. Two additional radiometric adjustments are applied to the completed orthos in Adobe Photoshop. The first is a sharpening mask filter; this filter is used to help increase sharpness of a digital image. The basis for this filter is to locate pixels that differ in value from surrounding pixels by the threshold specified. It then increases the pixels contrast by the value identified. For neighboring pixels specified by the threshold, the lighter pixels get even lighter and the darker pixels get even darker based on the specified amount. The changes made maintained the integrity of the original histogram curve. The final digital ortho product was GEOTIFF files."

in U.S. Geological Survey

USGS Earth Resources Observation and Science Center
Sioux Falls SD, 57198-0001, USA

phone: 605.594.6151
fax: 605.594.6589
hours: 0800 - 1600 CT, M - F (-6h CST/-5h CDT GMT)
Data received at EROS were verified as:
Projection: NAD_1983_UTM_Zone_18N
Resolution: 0.3000 m
Type: Natural Color
and resampled to align to the USNG using the USGS Seamless system. The naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage. The naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage. The metadata were imported and updated for display through The National Map Server at Chip-level metadata are provided in XML format.

Distribution

Distribution liability
Although these data have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made by the USGS regarding the use of the data on any other system, nor does the act of distribution constitute any such warranty. Data may have been compiled from various outside sources. Spatial information may not meet National Map Accuracy Standards. This information may be updated without notification. The USGS shall not be liable for any activity involving these data, installation, fitness of the data for a particular purpose, its use, or analyses results.

Distributed by

in U.S. Geological Survey

Earth Resources Observation and Science Center
Sioux Falls SD, 57198-0001, USA

phone: 605.594.6151
fax: 605.594.6589
hours: 0800 - 1600 CT, M - F (-6h CST/-5h CDT GMT)

Metadata

FGDC Content Standards for Digital Geospatial Metadata / FGDC-STD-001-1998 as of 2012

Provided by

in U.S. Geological Survey

USGS Earth Resources Observation and Science Center
Sioux Falls SD, 57198-0001, USA

phone: 605.594.6151
fax: 605.594.6589
hours: 0800 - 1600 CT, M - F (-6h CST/-5h CDT GMT)