Layer: raster.RASTER.AERIAL1977

Name: raster.RASTER.AERIAL1977_1FT

Display Field:

Type: Raster Layer

Geometry Type: null

Description: Kucera performed 1”=1200’ and 1”=2500’ scale, black and white aerial film photography covering most of Boulder County in the spring and summer of 1977. The aerial coverage consists of approximately 1200 9”x9” photo exposures. Land Use has two nearly complete sets of contact prints from the flight. These have metadata printed on the contact prints, as was typically done at the time with aerial photography. Images from this flight were processed by Kucera onto Mylar at 1"=200' scale with one PLSS section per sheet. It is not known if these Mylar images were orthorectified. The specific date of the photo is printed on the Mylar. Land Use has the Mylar set. The contract for the flight has not been found, but an exhaustive search has not been conducted. Starting in 2016, the Land Use Department contacted Kucera to see if the contact prints could be scanned and orthorectified to produce digital imagery suitable for use in the County’s GIS. It was found that Kucera had most of the original film negatives in storage and some of the control data used for the flight. On May 24, 2018 a contract was approved with Kucera to scan the film negatives at 1200 dpi on a Zeiss Photo Scan photogrammetric scanner to yield digital photo imagery with 1’ resolution. Digital aerotriangulation of the scanned imagery was done using control coordinates read from existing County orthoimagery for ground features identifiable commonly in the scanned aerial imagery and in the existing orthoimagery. Orthorectification of the triangulated aerial photo imagery using the best available digital elevation model (DEM) coverage of the County. Mosaicing of the orthorectified images and division of the mosaiced imagery into coordinate grid bounded, seamlessly matched orthoimage tiles was performed. THERE ARE BREAKS AND MISALIGNMENTS IN THE IMAGERY. The breaks are inherent radial image displacements within and across the overlapping exposures of the aerial photo imagery, due to camera lens distortions, aircraft tip/tilt, and scale variation from changes in terrain relief. Rectification was limited because suitable triangulation of the historical aerial photo imagery was limited due to a number of issues, including lack of camera calibration and flight reports, fiducial marks not well defined, differing photo scales, and reflights in varying directions. There are also tone/lighting differences between flight lines of the film photo capture, this is most noticeable when looking at the imagery at a countywide scale. Final delivery of the imagery was made in May 2019. The imagery was delivered to the County by FTP in MrSID format. The Land Use Department converted the MrSID imagery to ESRI GRID format, then converted the imagery to an ESRI Enterprise Geodatabase raster (for unknown reasons the direct conversion from MrSID to ESRI Geodatabase raster proved problematic).

Copyright Text: Boulder County

Default Visibility: true

MaxRecordCount: 0

Supported Query Formats: JSON, geoJSON

Min Scale: 0.0

Max Scale: 0.0

Supports Advanced Queries: false

Supports Statistics: false

Has Labels: false

Can Modify Layer: false

Can Scale Symbols: false

Use Standardized Queries: true

Extent:

Drawing Info:

N/A Advanced Query Capabilities:

HasZ: false

HasM: false

Has Attachments: false

HTML Popup Type: esriServerHTMLPopupTypeNone

Type ID Field: null

Fields: None

Supported Operations: Query Query Attachments Generate Renderer Return Updates

Iteminfo Thumbnail Metadata

Layer: raster.RASTER.AERIAL1977_1FT (ID: 0)