| Tile: 4012SW 8-bit Color Infrared SW Quadrant of PINE LAKES | |
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Coordinate system: Universal Transverse Mercator Theme keywords: ImageryBaseMapsEarthCover, orthorectified, orthophoto, orthoimagery, Infrared (IR), framework, Digital, DOQQ |
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Abstract:
<abstract>
This dataset is a single orthophoto from a collection of GeoTIFF
format color infrared orthophotos covering the St. Johns River Water
Management District.
An orthophoto is remotely sensed image data in which displacement of
features in the image caused by terrain relief and sensor
orientation have been mathematically removed. Orthophotography
combines the image characteristics of a photograph with the
geometric qualities of a map. Each orthophoto provides imagery for a
nominal 3.75 minute (in latitude and longitude) cell area. The
source imagery was obtained from December 2003 to March 2004 and used to produce
orthophotos with a one meter ground resolution. Imagery was acquired
at 0.62 meter ground sample distance (GSD) resolution. Flight height
maintained during mission was 20,000 feet AGL. The imagery was captured
at 12-bit radiometric resolution and converted to 8-bit radiometric
resolution during post processing. The imagery was captured with 20%
sidelap between all adjacent flight lines. The SJRWMD project area
was divided into 5 flight blocks due to necessary base station and
flight line length requirements. The imagery was obtained and processed
by all digital means beginning with data acquisition using a Leica ADS40
Digital Airborne Sensor. The orthophotos are available in GeoTIFF form.
The projected coordinate system is UTM zone 17 N, NAD 83 HARN, GRS 80, Units Meters.
</abstract> |
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Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
<abstract> This dataset is a single orthophoto from a collection of GeoTIFF format color infrared orthophotos covering the St. Johns River Water Management District. An orthophoto is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthophotography combines the image characteristics of a photograph with the geometric qualities of a map. Each orthophoto provides imagery for a nominal 3.75 minute (in latitude and longitude) cell area. The source imagery was obtained from December 2003 to March 2004 and used to produce orthophotos with a one meter ground resolution. Imagery was acquired at 0.62 meter ground sample distance (GSD) resolution. Flight height maintained during mission was 20,000 feet AGL. The imagery was captured at 12-bit radiometric resolution and converted to 8-bit radiometric resolution during post processing. The imagery was captured with 20% sidelap between all adjacent flight lines. The SJRWMD project area was divided into 5 flight blocks due to necessary base station and flight line length requirements. The imagery was obtained and processed by all digital means beginning with data acquisition using a Leica ADS40 Digital Airborne Sensor. The orthophotos are available in GeoTIFF form. The projected coordinate system is UTM zone 17 N, NAD 83 HARN, GRS 80, Units Meters. </abstract>
The goal of this project is to update the St. Johns River Water Management District's digital orthophoto quarter quadrangle (DOQQ) database. The DOQQ database was originally created in 1994 and updated in 1999, and this project represents the iteration. The DOQQ database has become the standard basemap for the District's Geographic Information System (GIS) and is widely used throughout Florida. This dataset is part of a broader statewide DOQQ mapping effort.
USGS 7.5-minute DEMs were used to orthorectify the ADS40 imagery. Some quarterquads along the coast are primary water, with only a small percentage of land area and surface elevations. In these quarterquads the error and uncertainty in the DEM surfaces increase, and can affect rectification of the imagery in ocean water areas as the distance from land increases. The accuracy of DEM data depends on the source and resolution of the data samples. DEM data accuracy is derived by comparing linear interpolation elevations in the DEM with corresponding map location elevations and computing the statistical standard deviation or root-mean-square error (RMSE). The RMSE is used to describe the DEM accuracy. For 7.5-minute DEM's derived from a photogrammetric source, 90 percent have a vertical accuracy of 7-meter RMSE or better and 10 percent are in the 8- to 15-meter range. For 7.5- and 15-minute DEM's derived from vector or DLG hypsographic and hydrographic source data, an RMSE of one-half of a contour interval or better is required.
Date of source imagery acquisition.
The St. Johns River Water Management District prepares and uses information for its own purposes and this information may not be suitable for other purposes. This information is provided "as is". Further documentation of this data can be obtained by contacting: St. Johns River Water Management District, Division of Integrated Application Systems, Post Office Box 1429, Palatka, Florida, 32178-1429, (386) 329-4500.
St. Johns River Water Management District
4049 Reid Street
Sample points taken from overlapping areas of adjacent image strips that contributed image chips to each orthophoto tile are typically consistent to the 2-3 pixel level. This not only ensures that a consistent mosaic can be created from the adjacent image strips acquired with the ADS40 pushbroom scanner but also means that the images have good precision and as a group are spatially self-consistent. When these images were compared to the most recent USGS available one meter orthophoto images (1999) good agreement (typical deviations of 2-4 meters) were observed. These two sets of compared images were produced by different methods and positional differences between them does not indicate that one set of images is more accurate positionally than the other. GeoTIFF headers are not standard USGS headers.
These data cover the entirety of St. Johns River Water Management District. Each orthophoto has an overedge of approximately 30 meters on all sides of its centering 3.75 minute cell. Cells that are on the edge of the district are sometimes smaller than the typical nominal 3.75 minute tile size.
Ground control consisted of photo identifiable surveyed points. Beyond necessary production requirements an additional 30% GCPs were collected for quality control checks. The imagery was collected at an altitude of 6096m using an ADS40 digital sensor. Image quality was verified during the post flight review phase. Factors considered during this review included but were not limited to the presence of smoke and/or cloud cover, contrails, light conditions and sun glint. The triangulated strips were rectified with a USGS DEM of the area. The vertical accuracy of the DEM varies based on the elevation postings and is generally estimated at 3-7m. The red, green and near infrared bands were combined to generate a final orthophoto. The ADS40 sensor collects twelve bit image data which requires radiometric adjustment for output in standard eight bit image channels. Converting to eight bit results in a reduction of the color range from 4096 to 256 - thus loss of radiometric detail is inevitable. The extra dynamic range of the sensor permits greater object differentiation in shadows and in bright areas. The sixteen bit dynamic range permitted the imagery to be more effectively color balanced than is possible with eight bit imagery. This was accomplished by performing tonal enhancements immediately prior to the reduction from sixteen bit to eight bit data. In addition to color balancing these eight bit images were adjusted to create seamless imagery to the highest extent practically achievable. The imagery was mosaicked using a combination of automated and manual seamlines generation. Project specified tiles were extracted from the mosaic. Final image tiles were reviewed for artifacts and anomalies and adjusted as part of quality control procedures. Adjacent images are compared for consistency in overlap regions. The images are reviewed for rectification problems such as bridge displacements caused by the underlying digital elevation model. When necessary, local corrections to the imagery were performed to minimize such effects.
3601 SW 2nd Avenue Suite Y
Metadata imported.
St. Johns River Water Management District
4049 Reid Street
The St. Johns River Water Management District prepares and uses information for its own purposes and this information may not be suitable for other purposes. This information is provided "as is". Further documentation of this data can be obtained by contacting: St. Johns River Water Management District, Division of Integrated Application Systems, Post Office Box 1429, Palatka, Florida, 32178-1429, (386) 329-4500.
There is no charge for downloading data from the District web site at http://www.sjrwmd.com. Data can be ordered on CD-ROM as instructed on the web site.
1. Use the District website: http://www.sjrwmd.com to download data, or 2. Call or email to organizations listed under Distributor.
3601 SW 2nd Ave., Suite Y