Nassau County 20 centimeter Resolution Color Infrared Orthoimagery

Metadata:


Identification_Information:
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Identification_Information:
Citation:
Citation_Information:
Originator:
Publication_Date: Summer 2005
Title:
Nassau County 20 centimeter Resolution Color Infrared Orthoimagery
Geospatial_Data_Presentation_Form: remote-sensing image
Series_Information:
Series_Name: NYS Digital Orthoimagery Program (NYSDOP)
Publication_Information:
Publisher: NYS Office of Cyber Security
Description:
Abstract:
This metadata record describes the 2004 digital ortho mapping of Nassau County, New York. The mapping includes production of Color Infrared digital orthophotography with a pixel of 6 inches using imagery collected with the Leica ADS40 digital pushbroom sensor and processed with the ISTAR system. Image horizontal accuracy is +/-4 ft. at the 95% confidence level.  Each file contains an image covering 750 meters by 750 meters on the ground.
Purpose:
This digital orthoimagery can serve a variety of purposes, from general planning to field reference for spatial analysis to a tool for revision of vector maps. It can also serve as a reference layer for GIS.
Supplemental_Information:
Digital elevation models used for orthorectification were compiled from several sources, all of which were compiled photogrammetrically.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: April 2004
Currentness_Reference:
ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Irregular
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -73.783176
East_Bounding_Coordinate: -73.411520
North_Bounding_Coordinate: 40.928136
South_Bounding_Coordinate: 40.565728
Keywords:
Theme:
Theme_Keyword_Thesaurus: Orthophoto, ortho
Theme_Keyword: Digital orthoimagery
Access_Constraints:
Use_Constraints:

Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Tim Ruhren
Contact_Organization: NYS Office of Cyber Security
Contact_Position: NYS GIS Clearinghouse
Contact_Address:
Address_Type: mailing and physical address
Address:
30 South Pearl Street
City: Albany
State_or_Province: New York
Postal_Code: 12207-3425
Country: USA
Contact_Voice_Telephone: 518-474-5212
Contact_Facsimile_Telephone: 518-473-5848
Contact_Electronic_Mail_Address: nysgis@dhses.ny.gov
Data_Set_Credit:

Native_Data_Set_Environment:
Raw ADS40 digital data in stereo pair equivalent.
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Data_Quality_Information:
Lineage:
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Data_Quality_Information:
Logical_Consistency_Report:
The dataset contains raster images or digital ortho images so the logical
consistency report is not applicable. The file naming convention was
supplied by New York state and is based on the co-ordinate pair of the lower
left corner of the ortho tile. When the ortho tiles were created the file
names were restricted to a numeric value representing the lower left corner
of the ortho tile. 10470162 which represented a tile with the lower left
corner of 1047000, 162000. These tiles were then all renamed using a batch
script so that they reflected the N.Y. state standard
l_10470162_06_5000_col_2004.tif Consistency of file naming was ensured by
the batch process.
Completeness_Report:
The project consisted of 1643 final tiles
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
+/-4 ft. at the 95% confidence level (NSSDA)
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
Not applicable.
Lineage:
Process_Step:
Process_Description:
The aerial imagery acquisition for Nassau County was flown to support the creation of digital orthophotography with a 6 inch pixel. The imagery was acquired in two sorties over two days with a total of 26 flight lines. The mission was flown at 4800 feet AMT using the Leica ADS40 sensor, SP3.
The airborne GPS data were processed and integrated with the IMU. The results were imported into the ISTAR system for use in the aerotriangulation. The ADS40 imagery was downloaded onto the EarthData server and brought over to the UNIX based ISTAR system. The ground control was used in conjunction with the processed ABGPS results for the aerotriangulation. The properly formatted ISTAR results were used for subsequent processing.
An initial surface and bridge location was provided to EarthData by VARGIS. The surface data was translated into ASCII xyz files. A bridge buffer routine was then run on the 3D bridges supplied by the VARGIS creating an apron around the bridges. Because there was insufficient data coverage to complete the ortho tiles it was necessary to generate and ISTAR DSM to supplement the provided surface. ISTAR digital surface modeling is based on an auto correlated pixel matching system within the ISTAR software. The auto correlated DSM surface represents the initial surface model. This surface is then exported from the UNIX format into a Microstation compatible format. The techniques used to create the ISTAR DSM auto correlated surface are similar to those used for LIDAR processing. EarthData has developed a unique method for processing DSM data to identify and remove elevation points falling on vegetation, buildings, and other aboveground structures.  The algorithms for filtering data were utilized within EarthData's proprietary software and commercial software written by TerraSolid.  This software suite of tools provides efficient processing for small to large-scale, projects and has been incorporated into ISO 9001 compliant production work flows. The following is a step-by-step breakdown of the process.
1. Using the DSM ISTAR data set created by EarthData, the technician performed a visual inspection of the data to verify that the flight lines met correctly. The technician also verified that there were no voids, and that the data covered the project limits. The technician then selected a series of areas from the dataset and inspected them where adjacent flight lines met. A process, which utilizes 3-D Analyst and EarthData's proprietary software was run to detect and color code the differences in elevation values and profiles. The technician reviewed this information and located the areas that contained systematic errors or distortions that were introduced by the auto correlation. 
2. Systematic distortions highlighted in step 1 were removed and the data were re-inspected.  Corrections and adjustments can involve the application of angular deflection or compensation for curvature of the ground surface that can be introduced by crossing from one type of land cover to another.
3.The data were checked against the control network to ensure that vertical requirements were maintained. The ISTAR DSM and the ASCII created from the VARGIS data were both merged together and imported back into the ISTAR UNIX environment.
The digital orthophotography was created with a 6 inch pixel. One complete sets of orthos were made covering the entire project area in Color Infrared. Once the processed merged DSM data was in the ISTAR system the initial radiometric adjustments were performed on the imagery for each flight line attempting to reach the best possible histogram. The rectification process was run using the processed DSM surface and the radiometrically balanced imagery on each flight line. A second set of radiometric adjustments were made and mosaic lines were placed. QA/QC was performed looking for smears and other indications of problems within the digital orthophoto creation process. The final imagery data set is removed from the ISTAR environment in a process called "packaging" where the individual tiles are created. The created tiles are reviewed again for anomalies and interactive radiometric adjustment applied where needed. The Color Infrared orthos utilized the red, green and blue bands. 
The final product was untiled and uncompressed TIF and GeoTIFF format digital orthos with supporting TFW files. Final quality control for horizontal accuracy and image
quality was performed by New York State.
Cloud_Cover: <1%
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Spatial_Data_Organization_Information:
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Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Pixel
Row_Count: 3750
Column_Count: 3750
Vertical_Count: 1
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Spatial_Reference_Information:
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Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 18
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999600
Longitude_of_Central_Meridian: -75.000000
Latitude_of_Projection_Origin: 0.000000
False_Easting: 500000.000000
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: row and column
Coordinate_Representation:
Abscissa_Resolution: 0.200000
Ordinate_Resolution: 0.200000
Planar_Distance_Units: meters
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
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Entity_and_Attribute_Information:
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Entity_and_Attribute_Information:
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Distribution_Information:
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Distribution_Information:
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Transfer_Size: 3286
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Metadata_Reference_Information:
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Metadata_Reference_Information:
Metadata_Date: 20040901
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: NYS OCS
Contact_Person: Tim Ruhren
Contact_Address:
Address_Type: mailing and physical address
Address:
30 South Pearl Street
City: Albany
State_or_Province: New York
Postal_Code: 12207-3425
Country: USA
Contact_Voice_Telephone: 518-474-5212
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Extensions:
Online_Linkage: <http://www.esri.com/metadata/esriprof80.html>
Profile_Name: ESRI Metadata Profile
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