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altimetry corrections


global currents

Above are examples of original figures available in editable PDF format. Select the images for larger figures and instructions for downloading the PDF.

altimetry corrections

Altimetry corrections. Download PDF (464 KB). CLOSE AND RETURN

geostrophy diagram

Geostrophic currents. Download PDF (335 KB). CLOSE AND RETURN

surface current map

Global surface currents. Download PDF (9.9 MB). CLOSE AND RETURN

What is the resource library?

The LearnEO! resource library is a collection of background information, analysis tools, illustrations, animations and much else collected from Bilko and LearnEO! lessons. Much of this material is general, and may be of interest also outside the lesson in which it was first developed.

The resource library allows you to find material you can adapt for your own use, for example to develop new tutorials, case studies or lessons. Building on existing resources should reduce the effort involved.

Licensing and copyright

All LearnEO! resources in this library are either public domain or available under a Creative Commons Attribution 3.0 Unported licence.
See licence terms

By making the material freely available, we hope to encourage LearnEO! users to develop and share their own material.

External resources

We also keep information on external resources such as on-line remote sensing courses. Material from external sources are not included in the Creative Commons licence terms that apply to LearnEO! material.



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Physical variables   more
Sensing techniques   more
Satellite missions   more
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Processing techniques   more
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Examples of available resources

To find other resources than the ones listed below use the keyword search and/or browse options above right.

Creative Commons License
Using Filters to Reduce Speckle Noise in SAR Data

Speckle is common in all coherent imaging systems such as synthetic aperture radar (SAR). It can be removed by smoothing data using adaptive or non-adaptive filters. This document compares different SAR speckle filters available in the Bilko software.
Source: LearnEO! Tutorial.   Credit: V.Byfield.   Licensed under a Creative Commons Attribution 3.0 Unported License.
Background information available as PDF document (4 pages, 20 MB) or Word document

Creative Commons License
A quick guide to altimetry corrections

Interactive web page showing how altimetry is used to measure sea surface height, and explaining the corrections that are necessary before the data may be used to calculate the speed of geostrophic currents.
Source: ESA GOCE iBook.   Credit: NOC / V.Byfield.   Licensed under a Creative Commons Attribution 3.0 Unported License.
Background information available as web page

Creative Commons License
Forest fire at Castel Fusano near Rome

Description of Castel Fusano pine forest near Rome, with location image. Details of the forest fires that occurred 3–4 July 2000, with before and after photos.
Source: LearnEO! Lesson 7.   Credit: F.Del Frate, M. Picchiani.   Licensed under a Creative Commons Attribution 3.0 Unported License.
Background information available as PDF document (2.5 pages, 0.6 MB) or Word document


Physical variables

Physical variable include sea surface salinity (SSS), sea surface temperature (SST), chlorophyll concentration, vegetation indices, surface reflectance, land vegetation indices, etc.

It also includes the speed and direction of currents, the behaviour of oil spills and surface slicks.

Sensing techniques

This category includes passive remote technique such as ocean colour (optical remote sensing), thermal infrared radiometry, passive microwave radiometry.

It also includes active techniques such as altimetry, synthetic aperture radar (SAR), scatterometry, lidar, laser fluorimetry etc.

Satellite missions

Earth observation missions include a specific satellite which orbits the Earth to gather data for environmental research and monitoring, as well as the ground segment, which collects the data that is transmitted back, processed to provide useful information and distributed to users. The satellite used in the mission acts as a platform for one or more sensors, and the mission is usually the name of the satellite.

ESA missions include ERS-1, ERS-2, Envisat, CryoSat, GOCE, SMOS, and in future the Sentinel satellites. Examples of NASA missions include Aqua, Terra, GRACE, Aquarius.


A satellite can act as a platform for one or more more instruments or sensors, which measure electromagnetic radiation at particular wavelengths or frequencies. ESA examples include ASAR, MERIS, AATSR, and RA-2 (on Envisat), SIRAL (the main instrument of CryoSat), and the EGG (the gravimeter on GOCE).

Other examples are Jason (the altimeter on the Jason-1 and 2 satellites), MODIS (on NASA's Terra and Aqua satellites), AVHRR (used on a series of NOAA polar orbiting satellites), and Seviri (on MeteoSat Second Generation - MSG) etc.

Processing techniques

This category includes information on data processing algorithms used for calculating geophysical parameters (e.g. temperature, chlorophyll, vegetation indices) from satellite data.

It also includes data analysis techniques such as preprocessing, geometric correction, noise reduction, edge detection, application of flags, principal component (or EOF) analysis, classification, neural networks etc.

Data products and data sources

This category includes information about data centres, data availability, and data products. It includes explanations of procecessing levels, such as Level 0 (raw data), Level 1B (geo-references top of atmosphere measurements), Level 2 (geophysical paratmeters), Level 3 (gridded, single-sensor products), Level 4 etc., and may include brief information about the processing needed to take data from a lower to a higher level.

It may also includes information about how to obtain different data products from space agencies and other data providers.


Models can be used with remote sensing data in different ways. They may assimilate satellite observations, for example to improve prediction and forecasting; they may be used to fill gaps in observational data sets; they may be used to aid data analysis and interpretation, or to support the development of algorithms for data processing.

Examples from the resource library include oil spill models, vegetation models, and conceptual models of ocean circulation.

Location information

This category includes geographical background information needed to aid interpretation of data from a particular location.

Examples range from global scale such as oceans (Atlantic, Pacific) through regional (e.g. Benguela Current, Amazon) to local (e.g. Rome).


Definition of variables etc.; may include information about the units used and relevant measurement techniques.

Examples range from global scale such as oceans (Atlantic, Pacific) through regional (e.g. Benguela Current, Amazon) to local (e.g. Rome).


Information on the use of satellite data to obtain useful information for scientific research, environmental monitoring, management of natural resources, to support the decision making process in different contexts.

Examples include forest mapping, monitoring of urban growth, habitat mapping, crop monitoring, marine productivity studies, fisheries management, oil spill detection.

Organisations and initiatives

Examples include the International Charter for Space and Major Disasters, the Black Sea Commission, the European Maritime Safety Agency Clean Seas project.

Wider science topics

These are wider topics from oceanography, geography, geophysics, geology, biology, ecology and other environmental sciences to which Earth observation data may contribute. The topics covered in this category are not specifically related to satellite remote sensing and its various applications, but may be of value in that they provide a wider context.

Examples of such topics include the 'global ocean conveyor belt' - the system of deep and surface currents, which play an important role in Earth's climate system and marine ecology. This system cannot be monitored with satellite data alone, but EO data makes an important contribution to our current knowledge of the contributing current systems.

Remote sensing handbooks, manuals and courses

More extensive education material teaching the principles of remote sensing. Examples range from the basics of remote sensing, through more specialist material dealing on specific sensing techniques through to handbooks for application areas such as tropical coastal management.

Animations and movies

Analysis tools

LearnEO! lessons include Bilko 'tools' such as formula documents, colour palettes and custom filters. Many of these are relatively general and may be used outside the lesson for which they were originally created. Some are specific to a particular instrument or data product (e.g. MERIS level 2 data); others are more general.

The LearnEO! resource library contains zip file that contain such Bilko tools with brief descriptions of how to use them, and how they may be modified if necessary.

External tools include links to free data analysis software available on-line.

Figures and diagrams

Many of the illustrations created for LearnEO! and Bilko lessons are originals, created by the lesson authors or their colleagues. These are available in PDF format, and may be edited for use in other contexts, such as lectures or new hands-on training resources. This allows users to open the files and edit them, for example by translating text into to a different language.

Not all the figures used in LearnEO! lessons and background documents are original artwork. If you do not find a figure you want in the resource library, this could be the reason why.

Creative Commons Attribution 3.0 Unported Licence Terms

You are free to:

Share - copy and redistribute the material in any medium or format.

Adapt - remix, transform, and build upon the material for any purpose, even commercially.

LearnEO! authors whose material is available under this licence cannot revoke these freedoms as long as you follow the license terms below.

Under the following terms:

Attribution - You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

No additional restrictions - You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.


You do not have to comply with the license for elements of the material in the public domain or where your use is permitted by an applicable exception or limitation.

No warranties are given. The license may not give you all of the permissions necessary for your intended use. For example, other rights such as publicity, privacy, or moral rights may limit how you use the material.

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Background information

Background information includes text and illustrations collected from LearnEO! or Bilko lessons and tutorials - usually available in PDF format. For registered LearnEO! authors the texts may also be available as documents (.DOC), which are easier to edit and adapt for new lessons.

The documents provide more information about a specific topic concerned with collection, processing, distribution or application of remote sensing data. We have divided the background information into the broad categories listed below. However, a document may span more than one of these.

  • Physical variable (e.g. SSS, SST, Chlorophyll). This can also include the behaviour of currents, oil spills, surface slicks etc.)
  • Remote sensing technique (e.g. ocean colour, passive microwave radiometry, radar altimetry, scatterometry, SAR).
  • Mission (e.g. Envisat, CryoSat, SMOS, Aqua)
  • Instrument (e.g. ASAR, MERIS, AATSR, RA-2, Jason, SIRAL, EGG).
  • Algorithms and data processing or analysis techniques (e.g., classification, preprocessing, noise reduction, neural networks).
  • Data centres, data availability and data products
  • Models (e.g. oil spill model, vegetation model)
  • Location Information (e.g. Australia, Pacific, Benguela, Amazon)
  • Applications (e.g. Forest mapping, ENSO, sea ice monitoring)
  • Organisations and initiatives (e.g., International Charter for Space and Major Disasters, Black Sea Commission)

You can refine a keyword search by selecting one or more of these categories using the form on the right


LearnEO! tutorials are developed to teach specific data proecessing or analysis techniques, which may be used in several application areas. Most are written for the Bilko software, and contain step-by-step instructions for implementing a particular technique using Bilko. However, they often contain more general information about a specific technique, and may be adapted for use with other image processing software.

LearnEO! tutorials may be available on-line in HTML format, or may be downloaded as PDF documents.

The library also includes links to remote sensing tutorials hosted on other web sites. These may be hands-on or more theoretical. If you want to include external tutorials in your search, make sure the External resources checkbox is checked.