Delaware 2012 Orthophotography

Delaware FirstMap

Data Source

https://firstmap.delaware.gov/arcgis/rest/services/DE_Imagery/DE_Imagery_2012/ImageServer

Description

This data set consists of 0.3-meter pixel resolution (approximately 1-foot), 4-band true color and near infrared (R, G, B, IR) orthoimages covering New Castle, Kent and Sussex Counties in Delaware. 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 photography 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 1700-meter by 1700-meter block on the ground. There is no image overlap between adjacent files. The projected coordinate system is Delaware State Plane Coordinate System Meters. </abstract><purpose> The 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 users. This data also supports The National Map. </purpose><supplinf> The project consists of an area of approximately 474 square miles covering the county of New Castle in Delaware. A total of 508 4-band true color and near infrared (R, G, B, IR) orthos were produced to cover this area. The bounding coordinates provided within the Spatial Domain Section represents a rectangle covering the total area in which the project is located.

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.

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. Seamlines mismatches are not corrected unless the overall displacement exceeds one meter.

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. Photography was flown during leaf-off in deciduous vegetation regions.

The horizontal positional accuracy and the assurance of that accuracy depend, in part, on the accuracy of the data inputs to the rectification process. The location of existing photoidentifiable ground control and aerotriangulation points were evaluated on the Geotiff image and compared with their ground values in order to determine an overall accuracy for each test block of orthoimages within the project. After image coordinate measurement was completed for each block, an RMSE for the diagonal error was calculated for the orthoimages within the block. This value is an estimate of the horizontal accuracy of the tile expressed in meters.

The digital imagery mission was composed of a total of 3 lifts. Imagery (1-ft, 0.3 meter GSD) was obtained at an altitude of 9,450 feet above ground level on 28 February and 6 March 2012. The missions were flown with a Leica ADS40 (Sensor Head 51 and 52). 

Credits

Digital Aerial Solutions, LLC

Access/Use Constraints

Public Domain Information with citation of the U.S. Geological Survey for products derived from these data.

Distribution Liability

Map software is provided ‘as-is’, without any express or implied warranty. In no event will boydsmaps.com be held liable for any damages arising from the use of this software. The user assumes all risks associated with the use of this software. boydsmaps.com will not be held responsible for any inaccuracies and no responsibility is assumed for damages or other liabilities due to errors, installation, accuracy, availability, use or misuse of the data presented.

Full Metadata Link

https://firstmap.gis.delaware.gov/pdfs/public/DEImageryMetadata.pdf

Downloadable Version for Offline Use

None available at this time.