Resolution: 0.3 Meters

Bands: 4-band: R,G,B, NIR

SanbornDelivered as 2010 tiles, same tiling scheme as 2002 imageryEach tile is 1.7km x 1.7km, 5667x5667 pixels, ~133 MB (TIF).SRS: NAD83 HARN Delaware State Plane metersScale: 1:2,400

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) digital camera with ABGPS and IMU. This imagery provides the data for the digital orthoimage. Imagery was acquired on the following dates - Lift Date 0103062012 06 Mar 2012 0203062012 06 Mar 2012

Horizontal and vertical control was used to establish positions and elevations for reference and correlation purposes and as input to the aerotriangulation process. Control consists of photoidentifiable surveyed ground control for ground reference. A total of 10 photoidentifiable ground control points were collected.

Airborne GPS (ABGPS) and IMU data are collected with an onboard dual frequency GPS survey unit and a corresponding IMU system in combination with the digital imagery. The GPS data provides the position of the imagery at the time of capture while the IMU system records instantaneous changes in position and attitude of the sensor. The GPS/IMU, base station, and ground control processing are an important step towards the development of accurate orthoimages.

Source Imagery - ADS40 (Sensor Head 51 and 52) Digital Camera Imagery Control - Airborne GPS/IMU supplemented with photo identifiable field control Aerotriangulation, Orthorectification - SOCET SET, ORIMA Elevation Model - USGS DEM Mosaic - OrthoVista The following describes the digital production sequence. 1. The raw ADS40 (Level-0) data and associated GPS and IMU data for each mission is downloaded from the hard drives and checked to confirm that no files have been corrupted and that all data can be successfully downloaded. 2. The GPS and IMU data are post-processed along with the base station data to produce a precise position and attitude stream for each line of imagery. Post processing uses the high frequency readouts of the IMU to verify the GPS data and to provide instantaneous positioning of each line of imagery between GPS recordings. Likewise, the IMU attitude data is corrected for bias/drift and transformed to real world coordinates by using the GPS data. This process creates Level-1 rectified imagery which is an approximately geo-positioned image. 3. The ADS40 production process uses aerial triangulation techniques to combine the short-term accuracy of the IMU with high global accuracy of GPS. In combination with the minimum required number of ground control points (GCPs), aerial triangulation delivers best fitting results on the ground. The extra information added to the system by automatic tie point measurements (APM) leads to very reliable orientation results where photogrammetric measurements serve to control IMU/GPS measurements and vice versa. 4. The results of the APM are run through a combined bundle adjustment process to further refine the measured image coordinates and the position and attitude values from IMU and GPS computed by IMU/GPS post processing. The bundle adjustment process equally compensates for systematic errors such as the misalignment between IMU and sensor axes, IMU/GPS drift, and the datum difference between IMU/GPS and ground control coordinate system. This results in a very accurate and precise determination of the parameters of exterior orientation which are later used for Orthorectification. 5. The orthorectification process uses the raw Level-0 data as the input imagery source to avoid repeated re-sampling of the imagery to yield the best possible image quality and accuracy. The raw Level-0 true color imagery is orthorectified to the DEM using the adjusted position and orientation results from the aerial triangulation phase. The orthorectified strip of imagery is called the Level-2 data. 6. The resulting images are then mosaicked and color balanced. 7. The final 1700-meter by 1700-meter tiles are clipped out and the imagery is output in uncompressed GeoTIFF format with no overlap. 8. The completed natural color digital orthophotos are checked for image quality. Minor artifacts are corrected using Adobe Photoshop in an interactive editing session. Digital tiles are assigned final names based on Delaware tiling grid.

4-band true color and near infrared orthoimagery is organized in four bands or channels which represent the red, green, blue, and near infrared (R,G,B,IR) portions of the spectrum. Each image pixel is assigned a triplet of numeric values, one for each colorband. Numeric values range from 0 to 255. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.

Resolution: 0.3 Meters

Bands: 4-band: R,G,B, NIR

SanbornDelivered as 2010 tiles, same tiling scheme as 2002 imageryEach tile is 1.7km x 1.7km, 5667x5667 pixels, ~133 MB (TIF).SRS: NAD83 HARN Delaware State Plane metersScale: 1:2,400

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) digital camera with ABGPS and IMU. This imagery provides the data for the digital orthoimage. Imagery was acquired on the following dates - Lift Date 0103062012 06 Mar 2012 0203062012 06 Mar 2012

Horizontal and vertical control was used to establish positions and elevations for reference and correlation purposes and as input to the aerotriangulation process. Control consists of photoidentifiable surveyed ground control for ground reference. A total of 10 photoidentifiable ground control points were collected.

Airborne GPS (ABGPS) and IMU data are collected with an onboard dual frequency GPS survey unit and a corresponding IMU system in combination with the digital imagery. The GPS data provides the position of the imagery at the time of capture while the IMU system records instantaneous changes in position and attitude of the sensor. The GPS/IMU, base station, and ground control processing are an important step towards the development of accurate orthoimages.

Source Imagery - ADS40 (Sensor Head 51 and 52) Digital Camera Imagery Control - Airborne GPS/IMU supplemented with photo identifiable field control Aerotriangulation, Orthorectification - SOCET SET, ORIMA Elevation Model - USGS DEM Mosaic - OrthoVista The following describes the digital production sequence. 1. The raw ADS40 (Level-0) data and associated GPS and IMU data for each mission is downloaded from the hard drives and checked to confirm that no files have been corrupted and that all data can be successfully downloaded. 2. The GPS and IMU data are post-processed along with the base station data to produce a precise position and attitude stream for each line of imagery. Post processing uses the high frequency readouts of the IMU to verify the GPS data and to provide instantaneous positioning of each line of imagery between GPS recordings. Likewise, the IMU attitude data is corrected for bias/drift and transformed to real world coordinates by using the GPS data. This process creates Level-1 rectified imagery which is an approximately geo-positioned image. 3. The ADS40 production process uses aerial triangulation techniques to combine the short-term accuracy of the IMU with high global accuracy of GPS. In combination with the minimum required number of ground control points (GCPs), aerial triangulation delivers best fitting results on the ground. The extra information added to the system by automatic tie point measurements (APM) leads to very reliable orientation results where photogrammetric measurements serve to control IMU/GPS measurements and vice versa. 4. The results of the APM are run through a combined bundle adjustment process to further refine the measured image coordinates and the position and attitude values from IMU and GPS computed by IMU/GPS post processing. The bundle adjustment process equally compensates for systematic errors such as the misalignment between IMU and sensor axes, IMU/GPS drift, and the datum difference between IMU/GPS and ground control coordinate system. This results in a very accurate and precise determination of the parameters of exterior orientation which are later used for Orthorectification. 5. The orthorectification process uses the raw Level-0 data as the input imagery source to avoid repeated re-sampling of the imagery to yield the best possible image quality and accuracy. The raw Level-0 true color imagery is orthorectified to the DEM using the adjusted position and orientation results from the aerial triangulation phase. The orthorectified strip of imagery is called the Level-2 data. 6. The resulting images are then mosaicked and color balanced. 7. The final 1700-meter by 1700-meter tiles are clipped out and the imagery is output in uncompressed GeoTIFF format with no overlap. 8. The completed natural color digital orthophotos are checked for image quality. Minor artifacts are corrected using Adobe Photoshop in an interactive editing session. Digital tiles are assigned final names based on Delaware tiling grid.

4-band true color and near infrared orthoimagery is organized in four bands or channels which represent the red, green, blue, and near infrared (R,G,B,IR) portions of the spectrum. Each image pixel is assigned a triplet of numeric values, one for each colorband. Numeric values range from 0 to 255. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.