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->Weather system observation

->Environmental monitoring

->Sea surface temperatures

->Ocean colour

->Vegetation indexing

->Third-party image processing

->Cloud classification

Weather system observation

The multi-spectral HRPT image opposite (bands 1, 2 and 4) shows Hurricane Bertha near Eleuthera in the Bahamas. As well as tracking hurricanes and storms, HRPT and CHRPT data can be used to study weather systems and determine cloud types, temperatures and sizes.

The TOVS data received by the system can be used, for example, to look at geostrophic wind fields at different altitudes, produce T-Φ and T-log(P) tephigrams and plot ozone mappings, using third-party software (such as PC-TOVS or University of Wisconsin ITPP).

Environmental monitoring

Green vegetation has a reflectance of up to 60% in the near infra-red band. The data from the band 2 (near infra-red) sensor can therefore be applied to the green plane of a multi-plane image to show green vegetation.

The magnified area of the image opposite shows a large area of scrubland in Brazil. This is indicated by the brown colour, caused by the low vegetation activity compared with the surrounding areas.

Sea surface temperatures

The image opposite is a McClain SST (sea surface temperature) product generated by the Dartcom iDAP display and processing software. It was produced from bands 2 (near infra-red), 4 and 5 (both thermal infra-red) of an HRPT image of the mouth of the River Plate, between Uruguay and Argentina. It was transformed to fit a Mercator projection, and a mask was applied to obscure the land, which is not relevant in an SST product.

The image clearly shows currents, boundaries between areas of different sea surface temperature and mixing of warm and cold water. The temperature of each pixel in the image can be obtained to an accuracy of 0.1°C.

SST products can be used to determine likely areas of fish feeding. Also, knowing the exact location and direction of travel of warm and cold currents can be vital in route planning to help reduce fuel consumption and voyage times.

Ocean colour

Feng Yun CHRPT images contain five more bands than HRPT images. Three of these are ocean colour, which enable features such as the algal bloom in the image opposite to be detected. The image is a colour composite of bands 1, 2 and 8 of a Feng Yun 1C CHRPT image, and has been enhanced using the Dartcom iDAP software. The areas of algal bloom (purple and magenta) are clearly visible.

Vegetation indexing

The image opposite was produced using the Dartcom iDAP software, and shows Northern Spain. It is a Normalised Difference Vegetation Index (NDVI) product, and was generated using the following formula:

(band 2 – band 1) ÷ (band 2 + band 1) × 255

This shows the vegetation activity over the land area. The higher the NDVI value, the more active the vegetation.

The image has been transformed to fit a Mercator projection and areas of sea have been removed from the image with a user-defined mask. All of this processing can be accomplished using the the Dartcom iDAP software, which includes a comprehensive formula language for product generation plus Blue Marble and Digital Elevation Model (DEM) masking facilities for land and sea masking.

Third-party image processing

In addition to a wide range of image processing facilities, the Dartcom iDAP viewing and processing software also provides file format outputs to enable further processing in a number of widely-used third-party image processing applications, such as PCI Geomatica, ERDAS IMAGINE and ENVI*. NOAA level 1B output is also available to allow importing of data into other processing packages, such as Space 2.

The multi-spectral image opposite shows approximately the same area as the SST product above (the mouth of the River Plate). It was exported to PCI Geomatica format from iDAP, then processed to show suspended sediment at the mouth of the river. The image shows a clear boundary between the sea (blue) and the sediment (magenta).

Cloud classification

The image opposite was produced from an HRPT image of Western France using PCI Geomatica. It is a cloud classification using a cluster analysis. The water and land areas were masked out and an unsupervised classification was carried out to identify up to eight cloud classes.

The results were then examined and labels assigned to each class, based upon interpretation and reference to a cloud chart giving the temperature ranges and brightness values in bands 1 and 2.

Where appropriate, two classes were merged so that the final classification contains only six classes, plus land and water.

Cloud classification legend
Low Stratocumulus
Low Stratocumulus
Medium Stratocumulus
Medium Stratocumulus
Fog (low cloud)
Fog (low cloud)
Thin Stratos
Thin Stratos

* PCI Geomatica, ERDAS IMAGINE or ENVI optional at extra cost.

Hurricane Bertha

HRPT image received from the NOAA 12 satellite on 10th July 1996, showing Hurricane Bertha over the Bahamas

Scrubland in Brazil

Scrubland in Brazil, between the Marapi and Paru de Oeste rivers, is clear on this HRPT image.

McClain SST product

A McClain SST product (Mercator-reprojected with land masking) showing sea surface temperatures and currents

Algal bloom

Areas of algal bloom off the coast of South-West England on an enhanced CHRPT image

NDVI product

A normalised difference vegetation index (NDVI) product generated using the Dartcom iDAP software, showing vegetation activity

Processed HRPT image

An HRPT image processed using PCI Geomatica software to show suspended sediment at the mouth of the River Plate

Cloud classification product

A cloud classification produced using PCI Geomatica software, enabling cloud classes to be identified quickly and easily