• Seamline Generation.
In order to avoid displacement problems and to provide a homogenous dataset,
seamlines were placed such that each pixel of the orthophoto mosaic was taken from
the image whose nadir position was closest to the pixel. For this purpose, seamlines
were generated automatically to find their best geometric position before being
edited manually along with natural features such as ground parcel boundaries,
roads, and watercourses.
• Seamline Editing.
In order of priority, the seam lines were edited to preserve the following features:
– Geometric continuity and integrity of road networks, buildings, and landscape
objects
– Buildings and other elements that are not on the DEM level
– Specular reflection on water surfaces
– Hot spots in urban zones
– Clouds and cloud shadows
– Blurred areas along the mosaic line
– Final radiometric correction
• Tile Creation.
The seamless orthoimage mosaic was organized based on the tile structure
defined. Orthophoto mosaic tiles were delivered in the GeoTiff (32-bit RGBI,
8 bits per channel) + World files format with a tile size of 10,000 Â 15,000 pixels,
i.e., 3000 Â 4500 m. The coordinate system is a transverse Mercator projection on
ITRF96 datum (epoch 2005.0) on the GRS80 ellipsoid.
• Radiometric Editing.
The radiometric editor allows for an interactive adjustment of individual images,
flight lines, or areas of imagery. During normal processing, OrthoVista6.2.1 matches
the colors, contrast, and intensity from one image to the next throughout the
processing areas. If the input images were fairly uniform in color, contrast, or
intensity, it was not always necessary to use the radiometric editor.
13.3.1.5 Radiometric Enhancement
Radiometric corrections were performed to reduce the influence of errors with
inconsistencies in image brightness values, which may limit the ability to measure
and interpret land parcel units in the agricultural areas.
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H. Erden and M. Aslan
In order to avoid displacement problems and to provide a homogenous dataset,
seamlines were placed such that each pixel of the orthophoto mosaic was taken from
the image whose nadir position was closest to the pixel. For this purpose, seamlines
were generated automatically to find their best geometric position before being
edited manually along with natural features such as ground parcel boundaries,
roads, and watercourses.
• Seamline Editing.
In order of priority, the seam lines were edited to preserve the following features:
– Geometric continuity and integrity of road networks, buildings, and landscape
objects
– Buildings and other elements that are not on the DEM level
– Specular reflection on water surfaces
– Hot spots in urban zones
– Clouds and cloud shadows
– Blurred areas along the mosaic line
– Final radiometric correction
• Tile Creation.
The seamless orthoimage mosaic was organized based on the tile structure
defined. Orthophoto mosaic tiles were delivered in the GeoTiff (32-bit RGBI,
8 bits per channel) + World files format with a tile size of 10,000 Â 15,000 pixels,
i.e., 3000 Â 4500 m. The coordinate system is a transverse Mercator projection on
ITRF96 datum (epoch 2005.0) on the GRS80 ellipsoid.
• Radiometric Editing.
The radiometric editor allows for an interactive adjustment of individual images,
flight lines, or areas of imagery. During normal processing, OrthoVista6.2.1 matches
the colors, contrast, and intensity from one image to the next throughout the
processing areas. If the input images were fairly uniform in color, contrast, or
intensity, it was not always necessary to use the radiometric editor.
13.3.1.5 Radiometric Enhancement
Radiometric corrections were performed to reduce the influence of errors with
inconsistencies in image brightness values, which may limit the ability to measure
and interpret land parcel units in the agricultural areas.
248
H. Erden and M. Aslan