Humboldt Bay Orthoimages

This data set consists of 0.5-meter pixel resolution, four band orthoimages covering the Humboldt Bay area. 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. Each orthoimage provides imagery over a DOQQQ with a 100-meter image overlap between adjacent files. The projected coordinate system is UTM Zone 10 North with a NAD83 datum.

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.

11350

Four band orthoimagery is organized in four color bands or channels which represent the red, green, blue and near infrared portions of the spectrum. Each image pixel is assigned a quadruplet of numeric values, one for each color band. Numeric values range from 0 to 4095. Areas where data is incomplete due to lack of full image coverage are represented with the numeric value of 0.

U.S. Department of the Interior, U.S. Geological Survey, 1996, Standards for Digital Orthophotos: Reston, VA.

These photographs were obtained for use by the OCM during the course of its development of potential products to fulfill its statutory mission. Although OCM is making these photographs available to others who may find the photographs of value, OCM does not warrant, endorse, or recommend the use of these photographs for any given purpose. OCM is providing these photographs "as is," and OCM disclaims any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. In no event will OCM be liable to you or any third party for any direct, indirect, incidental, consequential, special, or exemplary damages or lost profits resulting from any use or misuse of these data.

None.

Data set is not for use in litigation. While efforts have been made to ensure that these data are accurate and reliable within the state of the art, NOAA, cannot assume liability for any damages, or misrepresentations, caused by any inaccuracies in the data, or as a result of data to be used on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty. We request that you credit the National Oceanic and Atmospheric Administration (NOAA) when you use these photos in a report, publication, or presentation.

ArcGIS 9.3.1; MicroStation v7; Z/I Imaging ISAT 5.3 and Orthopro 5.3

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.

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.; Quantitative Value: 0.948 meters, Test that produced the value: Federal Geographic Data Committee, 1998, Geospatial Positioning Accuracy Standard, Part 3, National Standard for Spatial Data Accuracy, FGDC-STD-007.3-1998

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. Imagery along the eastern margin of the urban area coverage and falling outside of the urban area may contain some void areas. These void areas have a radiometric value of 0 (black).

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 one meter.