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  • PAG 1998 Regional Digital Orthophoto Project


    The Pima Association of Governments (PAG) and a number of local government jurisdictions participate in the Regional Orthophoto Project which started with this 1998 project and continues with updates every few years.

    The orthophoto projects for the various years are all different. Differences include methods, coverage areas, elevation modeling, resolution, and spectra (black and white or color).

    The 1998 project includes:

    • 1 foot resolution panchromatic (black and white) imagery of 581 (578??) sections of selected areas in eastern Pima County.
    • 1 meter resolution multispectral (color) imagery of 546 sections of selected areas in eastern Pima County.
    • DEM elevation data for 240 sections of the project area.
    • DTM elevation data for 369 sections of the project area.
    • Contours for 341 sections of the project area.


    See the PAG 1998 Project Map.

    The 1998 Report on the Regional Digital Orthophoto Project includes information on:

    The 1998 project data was gathered (flown) in April, 1998.


    Multispectral (color) imagery horizontal accuracy specification:

      95% of all planimetric features that are well defined on the photograph shall be accurate to at least +/-3.0 feet of its true coordinate position.  The remaining 5% are displaced by no more than +/-6.0 feet.

    Description of 1998 Digital Orthophotography Images and Data

    Horizontal control is referenced to the Arizona State Plane Coordinate System Central Zone NAD83 High Accuracy Reference Network (HARN), or High Precision GPS Network (HPGN). These can be thought of as a higher order adjustment of NAD83. Vertical control is referenced to the North American Vertical Datum of 1988 (NAVD88). Elevations are specified in units of international feet.

    Type Resolution/Format Additional Information
    Panchromatic Images (Black & White) Grayscale: 1,2,4,8,16 foot TIFF format Images include an associated ASCII "world file" providing real-world transformation parameters
    Multispectral Images (Color) 1 meter resolution Lan format (ERDAS) Red, Green, Blue, Near-Infrared spectral bands
    Digital Elevation Models (DEMs) ASCII-format file Vertical Control referenced to both NAVD88 and NAVD29 International feet units
    Digital Terrain Models (DTMs) ASCII-format file Vertical Control referenced to both NAVD88 and NAVD29 International feet Units Two primary datafile types: point files(mass and grid points) and line files(breaklines and exclusion boundaries)
    2 Foot Contours E00 ArcInfo ASCII-format file E00 format file can be imported into ArcView 3.x

    See the 1998 Orthophoto Data Set Specifications from the Pima Association of Governments for more. Also see our Pima County MapGuide Maps which includes not only the imagery and topography (elevation information), but also a group of "Orthophoto Project Area" layers which show the coverage of various project products.

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