| Product |
An object that contains remote sensing data for a scene on the earth. A product can contain meta-data,
geo-coding
information, tie-point grids and bands. All band raster datasets within
a product have the same pixel resolution and share the same geo-coding.
|
| Band |
A raster dataset of a product. The band's sample values are usually the
measurements of a sensor.
|
| Tie-point grid |
An auxiliary (geophysical) raster dataset of a product. Tie-point grids usually provide less sample values
than a band. Missing values, with respect to the full pixel resolution of a product, are obtained by a
linear interpolation. The tie-point grid data normally does not originate from the sensor which
provided
the product's measurement data.
|
| Geo-Coding |
Provides the geodetic co-ordinates for a given pixel of a product.
An image is geo-coded if it is somehow possible to find the geographical latitude and longitude values for
any pixel.
ENVISAT products store their geo-coding information in the tie-point grids
named latitude and longitude. If a product has been map transformed,
it is known to be geo-referenced and as such, tie-point information is no longer required.
|
| Geo-Reference |
An image is geo-referenced if any point in the image can be found in a corresponding reference
map by a linear transformation. Every pixel in the image has the same size if expressed in map units.
Geo-referencing a
geo-coded image includes image warping, applying a well known map projection and pixel re-sampling.
|
| Map |
Graphic representation of the physical features (natural, artificial, or both) of a part or the whole of the
Earth's surface, by means of signs and symbols or photographic imagery, at an established scale, on a
specified
projection, and with the means of orientation indicated.
|
| Map Projection |
Orderly system of lines on a plane representing a corresponding system of
imaginary lines on an adopted terrestrial or celestial datum surface. Also,
the mathematical concept for such a system. For maps of the Earth, a projection
consists of a graticule of lines representing parallels of latitude and
meridians of longitude or a grid.
|
| Graticule |
Network of parallels and meridians on a map or chart. A geographic graticule is a system of coordinates of
latitude and longitude used to define the position of a point on the surface of the Earth with respect to
the
reference ellipsoid.
|
| Grid |
In connection with maps: a network of uniformly spaced parallel lines intersecting at right angles.
When superimposed on a map, it usually carries the name of the projection used for the map – that is,
Lambert grid,
transverse Mercator grid, universal transverse Mercator grid.
|
| Pixel coordinates |
Pixel values always refer to the upper
left corner of the pixel. Pixel co-ordinates are always zero based, the pixel at X=0,Y=0 refers
to the upper left
pixel of an image and the upper left corner of that pixel.
|
| Pixel value |
In general a composite of red, green and blue sample values resulting in a colour as part of an
image.
|
| Geodetic co-ordinates |
Geodetic co-ordinates are given as latitude and longitude values and always refer -
if not otherwise stated - to the WGS-84 ellipsoid.
The geodetic co-ordinates of a pixel, always refer to the upper left corner of the pixel.
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