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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
A unique characteristic of a raster function is that it stores process
definitions with the data instead of storing processed pixels. Upon
request, the function processes the pixels at the required
resolution and extent—not necessarily the whole image. This
reduces the processing time by avoiding processing pixels that are
not needed and avoiding writing pixels to disk unnecessarily.
Figure 1 is an example of a hillshade function that is applied to a
TIFF file containing DEM data. You can simply change the
azimuth parameter of the function dynamically to produce
different display results.
Azimuth = 45
iz fe Hilshade Function ..........
R5 dem9 110 46 .......
“Azimuth =
Figure 1. A dynamic display of hillshade at azimuth
of 45 and 135 from a DEM file
Multiple raster functions can be chained together to create a
composite function. The advantage of composite functions is that
one does not need to output intermediate results; instead they can
produce the final image directly and quickly. The example below
contains a Composite Band function which composes a multi-
spectral image from bands stored in separate TIFF files, a stretch
function, and then a clip function that clips a portion of the image
based on an area of interest. All the processes are being done on-
the-fly without intermediate results being created.
ii fie Clip Function
ii fx Stretch Function
i fa Composite Band Function
i. A
| 7019991002, 210. nn10.tif
i. fy RasterInfo Function
S ds p045r028 7t19991002 z10. nn20.tif
fx RasterInfo Function
48i pO45r028. 7t19991002, z10. nn30.tif
i fx RasterInfo Function
2 p045r028_7t19991002_210_nn40.tif
i= fy RasterInfo Function
| 486 p045r028_7t19991002_z10_nn50.tif
&-fe RasterInfo Function ;
46 p0451028_7t19991002_z10_nn70.tif ba *
Figure 2. A function chain from multiple images to create a
RGB display of an area of interest
The use of the raster function reduces the disk space usage and
time taken to process the image by avoiding writing the
intermediate results on disk and by processing only the requested
pixels. The raster function provides a foundation for dynamic
image processing and it is being used in two data models in
managing and using remote sensing images.
2.2 Raster Product
A raster product is a data model for accessing the image products
of single image scene. It is the implementation of the raster
function concept to the supported sensor platforms. When you
browse the image metadata file from ArcGIS's Catalog window,
the system will automatically construct a raster function chain
95
based on sensor specific metadata information from the image
scene and produce virtual views of the raster products. In this
example of a Landsat 7 ETM+ image scene, ArcGIS’s Catalog
window allows you to browse the raster product from the .met file
and directly access the multi-spectral product, the panchromatic
product, the pan-sharpened product, and the thermal product of
that image scene (Figure 3). Simply drag and drop any product to
ArcMap, and you will get a fully processed raster product that is
ready to use. The function chain (Figure 4) shows the image
processes that are performed behind the drag-and-drop operation.
Est View fevkeenks bueto Wesuon
8 es +
Figure 3. Raster products from a Landsat 7 ETM+ scene
iif Pansharpen_p045r028_7t19991002
zi fie Stretch Function
A Pansharpening Function
Jy Convolution Function
i+ fy RasterInfo Function
18 po45r028, 7p19991002, 210, nn&0.tif
i fy Extract Band Function
i. fy Composite Band Function
i fy RasterInfo Function
S88 po45r028, 7t19991002, 210, nni0.tif
- x RasterInfo Function
dm pO45r028 7t19991002 210 nn20.tif
asterInfo Function
Ze pO45r028 7t19991002 z10 nn40.tif
- fy RasterInfo Function
LS p045r028_7t19991002_210_nn50.tif
fy. RasterInfo Function
i85 pO45r028. 7t19991002, 210, nn70.tif
Figure 4 A raster function chain of the
Pansharpen product
The raster product data model shields the complicated image
processing steps and provides users with direct access to remote
sensing image products that can be used in GIS applications.
ArcGIS supports raster products for most commercial satellites
such as Landsat, QuickBird, IKONOS, GeoEye, WorldView, and
so on. For a complete list of supported products, visit the ArcGIS
product Help system at http://resources.arcgis.com/.
2.3 Mosaic Dataset
The mosaic dataset data model is designed for handling multiple
image scenes. It supports data from many sensor platforms. The
mosaic dataset can be used to catalog a large image collection and
virtually mosaic them into a seamless image mosaic. Furthermore,
mosaicking and cataloging capabilities of the mosaic dataset can
