This data set is a countywide mosaic of 1:20,000-scale, black & white aerial photos.
It was developed by scanning and orthorectifying 282 individual photographs, and
combining a subset of the resulting digital images into the mosaic. The final
orthophoto mosaic combines the image characteristics of the source photographs
with the geometric qualities of a map.
In addition to the hardcopy photos, the primary data sources used in the photo
orthorectification included 1998 1:12,000-scale Digital Orthophoto Quarterquads (DOQS)
and 30-meter Digital Elevation Models (DEMs).
The mosaic is provided in IMAGINE (*.img/.ige) format. A MrSID (*.sid) version of
the mosaic is also available, but image quality may be poorer due to the compression
applied. The 282 individual orthophotos, in .tif format, are also available.
The normal orientation of the data is by lines (rows) and samples (columns). Each line
contains a series of pixels ordered from west to east with the order of the lines from
north to south. The radiometric image brightness values are stored as 256 gray levels
ranging from 0 to 255.
Note that sections of this metadata record, in particular the Data Quality section,
describe the processing performed on the individual photos used to generate the mosaic.
Purpose:
This mosaic of historic orthophotography provides a visual perspective of the landscape
in the early 1970's. Due to its geometric qualities, it is useful as a reference layer
in a geographic information system, and provides a valuable tool for land use mapping
and change analysis.
Supplemental_Information: Data distribution tile: county
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19740320
Ending_Date: 19741024
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -71.261116
East_Bounding_Coordinate: -70.773671
North_Bounding_Coordinate: 43.589150
South_Bounding_Coordinate: 43.050544
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Digital orthophoto
Theme_Keyword: Digital image map
Theme_Keyword: Aerial photograph
Theme_Keyword: Rectified photograph
Theme_Keyword: Rectified image
Theme_Keyword: Orthophoto
Theme_Keyword: Historic
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: United States
Place_Keyword: Northeast
Place_Keyword: New England
Place_Keyword: New Hampshire
Place_Keyword: Strafford County
Temporal:
Temporal_Keyword_Thesaurus: None
Temporal_Keyword: 1974
Temporal_Keyword: 74
Access_Constraints:
Acknowledgement of GRANIT is appreciated in products derived from these data.
Use_Constraints: Not for legal use.
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Complex Systems Research Center, University of New Hampshire
During scanning, the paper positive image brightness and contrast values were
collected with a minimum of image quality manipulation. However the scanning
process may have changed some of the source brightness values. Once the
photography was in digital format, limited brightness and contrast manipulation
was performed to improve image quality.
Image brightness and contrast values may also deviate from the brightness values
of the original imagery due to image value interpolation during the rectification
processes. Radiometry of the rectified imagery was verified by visual inspection
of the digital orthophoto with the original unrectified image.
Slight systematic radiometric differences can be detected between adjacent orthophoto
files due primarily to differences in source photography capture dates and sun angles
of aerial photography along flight lines. These differences can be observed in an
image's general lightness or darkness when compared to adjacent orthophoto file
coverages.
Logical_Consistency_Report:
All orthophoto imagery was visually inspected for completeness to ensure that no
gaps or image misplacement occurred in the image mosaic area.
Completeness_Report:
All orthophotos are cloud free within the image area.
Source photography may be leaf-on or leaf-off in deciduous vegetation regions,
depending on the acquisition date of the original imagery.
The countywide product was derived by mosaicking every second image from the complete
collection of orthophotos. Due to standard overlap areas in the source photography,
this was sufficient to ensure complete, seamless coverage of the county while
avoiding the incorporation of excess data.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
The horizontal accuracy of each input orthophoto was expressed as an estimated root
mean square error (RMSE). The maximum RMSE for all orthophotos used to compile the
mosaic was < 1.
Additionally, visual inspection of the countywide mosaic was performed to compare
the planimetric (X and Y) coordinates of selected points with the coordinates of
the same points as determined from the reference orthophotos.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: USDA-APFO
Publication_Date: 1974
Title: 74photo(roll#)-(photo#)
Publication_Information:
Publication_Place: Salt Lake City, UT
Publisher: USDA-APFO
Online_Linkage: N/A
Source_Scale_Denominator: 18000
Type_of_Source_Media: Paper positives
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19740320
Ending_Date: 19741024
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: PHOTO1
Source_Contribution:
Panchromatic NAPP or NAPP-like photographs provided
the primary source for the countywide mosaic.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Complex Systems Research Center, University of New Hampshire
Publication_Date: 19990301
Title: Digital Elevation Model
Publication_Information:
Publication_Place: Durham, New Hampshire
Publisher: Complex Systems Research Center, University of New Hampshire
Horizontal control used to establish positions for reference and correlation purposes.
Process_Step:
Process_Description:
The source photos (PHOTO1) were converted to digital raster image files (*.tif
format) by scanning the paper positives with a Microtek Scanmaker 9800XL. A
scanning resolution of 600 dpi was used in the process, which converted the
photographic image densities to gray scale values ranging from 0 to 255 (for
black and white photographs). The resulting raster image files were degraded
to 400 dpi using Adobe Photoshop to reduce file size. Autoleveling of the
images was performed to standardize gray scale values as much as possible
across all images and to improve general image quality.
Imagine (v8.6) ORTHOBASE was then used to generate orthophotos from the scanned
images. In addition to the images, the following inputs were required: a user
parameter file (or "block" file) to control the rectification process, a digital
elevation model (DEM2) gridded to user specified bounds (with associated
projection, zone, datum and X-Y units), scanned digital image reference files
(DOQ3) covering the project area (also with associated projection,
zone, datum and X-Y units), ground X-Y-Z point values and their conjugate photo
coordinates in the camera coordinate system, calculated tie point values and
their conjugate photo coordinates in the camera coordinate system and
measurements of the fiducial marks in the digitized images.
Typically, a camera calibration report provides data on the focal length of the
camera and the distances in millimeters from the camera's optical center to the
camera's 4 fiducial marks. These marks define the frame of reference for spatial
measurements made from the photograph. The report was obtain from the USDA-APFO
office and the information there in was enter into IMAGINE.
Ground control points (GCP's) were acquired by comparing positions visible in
both the reference files (DOQ3) and the scanned digital image files.
The standard number of GCP's per image was between 10 and 25, and placement was
distributed throughout each scanned digital image file. GCP's were measured from the
reference files in NH State Plane feet, NAD83. The conjugate positions of the GCP's
on the scanned images were measured and recorded in camera coordinates.
In addition to collecting horizontal control (X-Y values) from the reference
files (DOQ3), DEM2 was used to collect a corresponding Z value for each GCP.
This Z-value aided in minimizing distortion caused by topographic variation
across the images.
Tie point values were generated by the software based on feature commonality in
the overlap/sidelap areas between multiple images. These points provided
additional control during the orthorectification process.
Based on the GCP's and tie points, RMSE's measuring the approximate "fit" of the
image transformation were calculated and reviewed. Points associated with values
in excess of 1 were relocated or rejected. With the final set of horizontal and
vertical control values, each image was orthorectified.
Quality control was conducted by comparing each newly rectified image to adjacent
newly rectified images to ensure proper overlay of common features. The digital
reference file (DOQ3) was also overlaid on the newly rectified images to ensure proper
transfer of coordinates. Once each image passed quality control, the edges were clipped
to extract just the core area of the image.
Imagine was then used to generate the countywide mosaic. Essentially, every
other photo was utilized, since that provided complete coverage of the area
while avoiding the processing of excess data. The resulting file is an
Imagine (.img/.ige) file.
Source_Used_Citation_Abbreviation: PHOTO1
Source_Used_Citation_Abbreviation: DEM2
Source_Used_Citation_Abbreviation: DOQ3
Process_Date: 200309
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Organization: Complex Systems Research Center
Contact_Person: GRANIT Database Manager
Contact_Position: GRANIT Database Manager
Contact_Address:
Address_Type: mailing and physical address
Address: Morse Hall, University of New Hampshire
City: Durham
State_or_Province: NH
Postal_Code: 03824
Country: US
Contact_Voice_Telephone: 603-862-1792
Contact_Facsimile_Telephone: 603-862-0188
Contact_Electronic_Mail_Address: granit@unh.edu
Hours_of_Service: 8:30AM-5PM, EST
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Pixel
Row_Count: 65111
Column_Count: 42736
Vertical_Count: 1
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: State Plane Coordinate System 1983
State_Plane_Coordinate_System:
SPCS_Zone_Identifier: New Hampshire
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999967
Longitude_of_Central_Meridian: -71.66666
Latitude_of_Projection_Origin: 42.500000
False_Easting: 984250.000000
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: Row and column
Coordinate_Representation:
Abscissa_Resolution: 3.000000
Ordinate_Resolution: 3.000000
Planar_Distance_Units: survey feet
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
For orthophotos from panchromatic sources, each pixel contains an 8-bit
gray-scale value between 0-255. A value of 0 represents the color black
while a value of 255 represents the color white. All values between 0
and 255 are represented as a shade of gray varying from black to white.
Entity_and_Attribute_Detail_Citation:
None
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Complex Systems Research Center
Contact_Person: GRANIT Database Manager
Contact_Position: GRANIT Database Manager
Contact_Address:
Address_Type: mailing and physical address
Address: Morse Hall, University of New Hampshire
City: Durham
State_or_Province: NH
Postal_Code: 03824
Country: US
Contact_Voice_Telephone: 603-862-1792
Contact_Facsimile_Telephone: 603-862-0188
Contact_Electronic_Mail_Address: granit@unh.edu
Hours_of_Service: 8:30AM-5PM. EST
Resource_Description: Downloadable Data
Distribution_Liability:
Digital data in NH GRANIT represent the efforts of the
contributing agencies to record information from the cited
source materials. Complex Systems Research Center, under
contract to the NH Office of State Planning, and in
consultation with cooperating agencies, maintains a
continuing program to identify and correct errors in these
data. OSP, CSRC, and the cooperating agencies make no claim
as to the validity or reliability or to any implied uses of
these data.
