Originator: Bret Hazell, GeoTerra, Inc., President
2015 Western Washington Regional Orthophotography - 4-band (RGBIr) with 2 Foot Pixel Resolution
Geospatial_Data_Presentation_Form: raster digital data
This data set contains 2 Foot, 4-band (RGBIr), 16-bit/band color orthophotography that covers a large and mostly contiguous urban area in the Puget Sound area of western Washington. An orthophotograph is an aerial photograph that is geometrically corrected using a 3D terrain surface so that the scale is uniform and the image lacks distortion, allowing for highly accurate horizontal measurement of most ground-level features.Over 1,200 square miles of digital aerial imagery suitable for 2 foot orthophotography was acquired by GeoTerra, Inc. in the spring of 2015 for the purpose of updating regional base mapping data. The regional project was a collaborative effort between multiple agencies primarily within the Puget Sound region. King County oversaw the project and acted as lead manager for the effort on behalf of 88 participants. The aerial imagery was acquired using multiple, large-format digital mapping cameras. Overlapping stereo imagery was aerially-triangulated into large block adjustments using new and existing surveyed control. Existing terrain data was updated, or in some areas newly acquired, and used for rectifying the aerial imagery into digital orthophoto mosaics. These ortho image files are in a 3000' x 3000' contiguous, non-overlapping tile structure and are available in uncompressed GeoTIFF format. Each are projected to NAD 83/91(HARN), Western Washington State Plane North Zone, US Feet.
This data set was produced to provide (2 ft) pixel resolution, 16-bit depth, RGBIr orthophotography for the 2015 Western Washington Regional Aerial update, a multi-agency collaborative project.
2 foot (2') pixel resolution orthoimagery for Western Washington, including all or parts of King, Snohomish, Kitsap, and Pierce Counties
Maintenance_and_Update_Frequency: None planned
Theme_Keyword: 4-band orthophotography
Theme_Keyword: aerial imagery
Theme_Keyword: RGBIr orthos
Theme_Keyword: Color infrared
Theme_Keyword_Thesaurus: ISO 19115 Topic Categories
Place_Keyword: King County
Place_Keyword: Pierce County
Place_Keyword: Snohomish County
Place_Keyword: Kitsap County
Place_Keyword: Skagit County
Access Constraints: Access to the digital files for the data from this project is limited to those participants who are listed in the contract between the county and GeoTerra, Inc. These participants signed a funding agreement with the county and paid a fee for the data they received. All participants are allowed to provide the data on public-facing websites to meet their internal business requirements. However, these public-facing sites cannot allow for download of the original data.
Use Constraints: This orthophotographic data was acquired and produced by GeoTerra, Inc for the 2015 Washington Regional Aerials Update per contract agreement with King County, Washington for aerial image acquisition, orthophotographic processing and delivery. Data is only to be used by the county and participants specified in the 2015 contract which states in the Licensing Terms that the County and participants: 1) may distribute the data to all parties with whom they are currently contracted, and 2) may distribute the data to private individuals for non-commercial purposes only, Exceptions to this Licensing Term may exclude those 2015 participants that purchased full ownership of their respective data areas. Full ownership of all data acquired and produced for the 2015 contract is retained by GeoTerra.
Horziontal accuracy of photo-identifiable features in the 3-inch orthophotography were measured and then compared with actual surveyed ground coordinates (QC checkpoints) to calculate statistical accuracy of the project. A 3rd party QC DAT Vendor (Miller Creek Aerial Mapping) peformed the QC analysis and determined that the 2015 project orthophotography meets or exceeds the horizontal acceptance criteria of RMSEr < 0.707 ft with a 95% confidence interval of < 1.224 ft.
Enhanced Aquisition Areas (EAA) were provided by King County and participants in shp format to assist in the identification of areas with excessive building height and density. These areas were used by GeoTerra duringflight planning and acquisition to enhance the number and density of photos as well as to capture these areas during maximum sun angles windows to help ensure minimal buidling lean and shadows exist in the final imagery.
3000' x 3000' tiling scheme in shp file format as provided by the King County technical manager to utilize for final ortho tile delivery.
New Survey Control was acquired by GeoTerra as needed to supplement the existing project ground control. All control, new and existing, was utilized to ensure the Aerial Triangulation block adjustment meets required accuracy standards.
Title: Various names
Source_Citation_Abbreviation: Various names
Multiple sources of existing DTM and DEM data as provided by King County and various participants. A large portion of the data was created for the 2012 regional ortho project and was provided to the 2015 contract vendor (GeoTerra) in DWG or DEM LAS format. More recent LiDAR data as acquired for various regional projects was also utilized. All DTM and DEM data was updated in a stereo environment using 2015 stereo imagery. Breaklines were added to bridges and some areas of change where applicable to help "hold the ground" in place during image rectification. Several existing datasets were identified by GeoTerra as not having the accuracy required to meet the 2015 project's 3-inch ortho specifications and were flown by GeoTerra for new LiDAR data in late 2015.
Title: Various names
Source_Citation_Abbreviation: Various names
Existing Survey Control data (in Excel and text format) as used for previous projects that fall within the 2015 procent extent. Control data was utilized in the Aerial Triangulation if still in existance or valid to ensure the resulting imagery was spatially accurate.
1. Flight Planning for image acquistion occured in March of 2015 prior to flight. Multiple aerial flight vendors were subcontracted by GeoTerra to help ensure imagery was captured in a timely manner given seasonal weather and sun angle constraints. The project was broken into multiple blocks suitable for concurrent and multi-flight acquistion. All flights were planned and flown to acquire photos with a minimum 60% forward overlap and 30% sidelap. Several areas of the project identifid as Enhanced Aquisition Areas (EAA) were incorporated into the flight plan which were based on the client's requirements for minimal shadows and reduction of lean of elevated strutures. These areas were flown during a two hour window of highest sun angle. EAA with tall buildings were specifically flown so that all photos were acquired with 80% froward overlap and 60% sidelap of imagery to help reduce lean of elevated buildings and structures.
3. Acquisition of 4-band, 16 bit/band, digital aerial imagery at less than 0.225 ft pixel resolution using multiple Vexcel UltraCam aerial mapping cameras (Hawk, X, Xp and Eagle) during leaf-off and high sun-angle conditions. Each flight occured with AGPS and IMU. Enhanced areas of acquisition were acquired at higher image overlap and during a high sun-angle window to minimize buidling lean and shadows in identified dense urban areas. Post-flight, raw images were processed using propietary UltraMap software into full-histogram (unclipped) images in a final *.TIF format.
4. Update of the existing Digital Terrain Model (DTM) to use for rectifying the images. Stereo photography, as a product of the aerial triangulation, was used to update the breakline and point data in a 3D stereo environment.
5. The most nadir portion of every photo was identified by creating "seamlines" used to stitch the rectified images together. Seamlines were created using a combination of automatic and manual methods. Inpho's Ortho Master software was utilized to collect or manually adjust the seamlines polygons.
8. After initial Quality Assessment (QA) of the tiles by GeoTerra, additional QA was performed by Miller Creek Aerials Mapping (MCA). This evaluation was both quantitative and qualitative and was performed for a high percentage of tiles in each production zone, usually 50-75%,or greater, of the tiles. Calls were defined geographically and attributed as to type of issue and signficance. The RGB tiles were also evaluated by affected participants via a ArcGIS Online data portal maintained by GeoTerra. Combined calls, those from MCA and from the participants, were assembled. Review by GeoTerra and MCA, and when needed, by a working group of participants resulted in a final call list of issues that required repair. Upon completion of all fixes, the tiles went through final approval by GeoTerra and MCA prior to being delivered to King County. The county then distributed the data to each participant for their defined area of interest.
Contact_Organization: Miller Creek Aerials Mapping
Contact_Person: Jimmy Shultz
Address: 19550 International Blvd, Ste 203
6. Rectification and mosaicing of all aerial photos using Inpho OrthoVista software, with the combined input of AT, updated DTM and seamlines.
Distribution Liability: This data was produced under a contract between GeoTerra, Inc and King County. Data may be distributed by the county and the other participants only as specified in the 2015 contract which states the Licensing Terms for the county and the other participants. Licensed participants may distribute the data only to other parties to who they are currently contracted and to private individuals for non-commercial purposes only. Certain participants are exceptions to the licensing terms (i.e., full ownership) and are not restricted in the data's distribution.