3.3 Imagery standards
97
Enhancements 0' the existing ISO 19100 standards
The work on the ISO 19129 is still ongoing. The following listing explains additional important enhancements of the existing ISO 19100 standards for the needs of
imagery.
• The ISO 19107 (Spatial schema) defines various surfaces such as a TIN. These
surfaces will be referenced for imagery purposes.
• The geometric transformations of spaceborne imagery data often require coordinate systems to describe the orbit of a satellite. These systems are fixed in relation
to the vernal equinox and are called Earth Centered Inertial (ECI) Coordinate
Reference Systems. They may be added to the ISO 19111 (Spatial referencing by
coordinates).
• The determination of the quality of imagery data requires visual and analytical inspection and evaluation methods. The quality of elevation models can be defined
with measures distributed in a regular pattern across the model. This method is
called "quality grid". The quality of imagery requires enhancements of the ISO
19113 and the ISO 19114.
• The portrayal of imagery data is often based on the application of Look-UpTables (LUT) or colour maps. The combination with vector-data often requires
scaling and rotation of the image. These aspects lead to an enhancement of the
ISO 19117 (Portrayal).
• A lot of ISO- and de-facto-standards exist for the encoding of imagery data.
Hardly any standards exist for the storage of associated metadata. The ISO 19129
describes two ways for the neutral encoding of imagery metadata:
1. General non-ISO picture coding and ISO-standardized XML for the metadata
encoding.
2. General non-ISO picture coding and ISO-standardized embedded metadata.
An example for the first method is the TIFF-world format. An example of the
second method is the TIFF-tags used in GeoTIFF. These requirements will lead to
an enhancement of ISO 19118 (Encoding).
The following paragraphs describe tesselations that are not explicitly defined in
the ISO 19123.
Tesselation is a method to order space. The ISO 19123 (Schema for coverage geometry and functions) contains a comprehensive definition of coverages. They comprise Thiessen polygons, quadrilateral grids, hexagonal grids, and TINs (Triangulated Irregular Network). For details see chapter 4, section 5. Additional tesselation
methods are required for imagery applications.
The tiled tessellation partitions the space according to regional aspects without
necessarily covering the complete area. It is used to partition a map series into single
map sheets. It is also used to define outset of a map in order to bridge empty areas
avoiding unnecessary data volumes. An example is a map of the U.S. showing Hawaii and Alaska on an extra tile.
ARiemann hyperspatial tessellation partitions aspace according to the density of
contents. Riemann has proven the applicability of the Euclidean geometry to the ndimensional space. Thus the Riemann space is called a hyperspace. The Riemann
97
Enhancements 0' the existing ISO 19100 standards
The work on the ISO 19129 is still ongoing. The following listing explains additional important enhancements of the existing ISO 19100 standards for the needs of
imagery.
• The ISO 19107 (Spatial schema) defines various surfaces such as a TIN. These
surfaces will be referenced for imagery purposes.
• The geometric transformations of spaceborne imagery data often require coordinate systems to describe the orbit of a satellite. These systems are fixed in relation
to the vernal equinox and are called Earth Centered Inertial (ECI) Coordinate
Reference Systems. They may be added to the ISO 19111 (Spatial referencing by
coordinates).
• The determination of the quality of imagery data requires visual and analytical inspection and evaluation methods. The quality of elevation models can be defined
with measures distributed in a regular pattern across the model. This method is
called "quality grid". The quality of imagery requires enhancements of the ISO
19113 and the ISO 19114.
• The portrayal of imagery data is often based on the application of Look-UpTables (LUT) or colour maps. The combination with vector-data often requires
scaling and rotation of the image. These aspects lead to an enhancement of the
ISO 19117 (Portrayal).
• A lot of ISO- and de-facto-standards exist for the encoding of imagery data.
Hardly any standards exist for the storage of associated metadata. The ISO 19129
describes two ways for the neutral encoding of imagery metadata:
1. General non-ISO picture coding and ISO-standardized XML for the metadata
encoding.
2. General non-ISO picture coding and ISO-standardized embedded metadata.
An example for the first method is the TIFF-world format. An example of the
second method is the TIFF-tags used in GeoTIFF. These requirements will lead to
an enhancement of ISO 19118 (Encoding).
The following paragraphs describe tesselations that are not explicitly defined in
the ISO 19123.
Tesselation is a method to order space. The ISO 19123 (Schema for coverage geometry and functions) contains a comprehensive definition of coverages. They comprise Thiessen polygons, quadrilateral grids, hexagonal grids, and TINs (Triangulated Irregular Network). For details see chapter 4, section 5. Additional tesselation
methods are required for imagery applications.
The tiled tessellation partitions the space according to regional aspects without
necessarily covering the complete area. It is used to partition a map series into single
map sheets. It is also used to define outset of a map in order to bridge empty areas
avoiding unnecessary data volumes. An example is a map of the U.S. showing Hawaii and Alaska on an extra tile.
ARiemann hyperspatial tessellation partitions aspace according to the density of
contents. Riemann has proven the applicability of the Euclidean geometry to the ndimensional space. Thus the Riemann space is called a hyperspace. The Riemann