BLIF2 (Blickpunkt Fernerkundung, i.e. focus on remote sensing). 

This application enables you to work with original satellite data in order to investigate the environmental transformations of your project.

Please visit the BLIF website for registration and login.

A PDF file of the BLIF manual can be accessed here.

The manual is also provided directly below:

1 Project Descriptions and objectives

BLIF2, which means “Blickpunkt Fernerkundung (i.e. focus on remote sensing)” is an educational project founded by the Educational University of Heidelberg. We created a web-based learning application, which enables students to deal with remote sensing approaches and gain insights in various methods of analyzing satellite data. Additionally, we designed learning materials perfectly fitting to different parts of the educational plan. BLIF2 is most appropriate for being used in Geography lessons, but it can also be applied for interdisciplinary courses, e.g. in combination with politics, economics, history or even biology. The access to BLIF2 is free of charge and easily practicable for every student or teacher.

1.1 Educational Potential of Remote Sensing

Working with the web-based learning platform BLIF 2.0…

· improves media competence

· offers an additional approach for dealing with certain geographic topics

· teaches you handling digital media

· increases your personal learning motivation

· broadens problem- and activity-oriented studying

· combines content-related with method expertise

· enhances independence and self-reliance

· offers insights in global issues and problems

· fosters critical thinking

2 References for course preparation

Students are forced to work independently with computers during BLIF-based lessons on global questions, e.g. socio-economic or environmental processes and transformations. To ensure a smooth operation, there are some things to keep in mind. We listed some aspects that should be considered during planning.

2.1 Technical Requirements

Usage of computers in class is often scaring to teachers due to unpredictable problems, which require complex and long-lasting solutions. In order to avoid such technical problems, the following requirements should be achieved when using BLIF2 in class:

· one of the following internet versions needs to be installed:

            Internet Explorer 7, Firefox 3.6, Google Chrome or Opera 11

· Java-Script has to be activated

· Cookies need to be activated

2.2 Content information

We provide some prefabricated worksheets, which can be downloaded on the BLIF homepage (http://blif.rgeo.de/cms/p/lernmaterialien/). Please note that you need to sign in to get full access to those materials. The table below provides some examples of topics for specific class levels. A complete list of all prefabricated materials is presented in chapter 3.1. The age levels proposed for each module can be interpreted as guidelines rather than definite rules. Some contents can easily be used across different age groups and be adapted to either a higher or lower level of knowledge.

Besides, it is possible to gain other satellite data to investigate personal issues. You can also use some of the provided picture details that simplify the selection of an appropriate study area. Chapter 2 explains both methods in detail.

2.3 Schedule Planning

All of the materials mentioned above are designed for about 2 lessons. While it is not recommended to reduce the processing time, it is possible to extend each of the modules. Working with BLIF2 requires basic knowledge on remote sensing and satellite data. Online-courses on the functionality of imaging satellites and the theoretical background of remote sensing techniques should be conducted before (e.g. by using SILC or FIS).

3 Topics

BLIF 2.0 focusses on issues of geographical, political or social relevance. All topics are compatible with the educational plan and easily to implement in the regular teaching structres. If you are interested in working with BLIF 2.0, please answer the following guiding questions to find an appropriate module:

• What ages do the students have? Which class would you like to work with?
• Which contents are in focus of your learning unit?
• Are you interested in a specific region (selection of a study area)?
• Have you compiled prior knowledge on this topic?
• Are there any data/materials available on BLIF 2.0 concerning this topic?
• Do you need additional material or data for analysis?

3.1 Available Resources

In between the prefactured materials different contents of geographical, political or socio-economical aspects are put in focus. Land-use changes are therefore investigated on a local, regional and even global scale. The range of issues contains different aspects of land-use, agriculture, hazards, environmental degradation, geology and resources, but even social structures and transformations. Each of the topics proposed is adapted to a specific age levels and fits perfectly with the educational plan.

All oft he prefabricated modules are available in two different versions, containing either a time-shift or a comparison of different locations with similar conditions. The analyses can be handled in partner work. The main task is o investigate either temporal or spatial changes.

All of the modules presented in the following table contain worksheets designed for independent processing. They refer to satellite data, which are available on BLIF 2.0. The worksheets also include a short introduction to a certain topic and lead through the steps of analysis. Some modules contain further materials for gaining background information.

3.2 Additional material

As an altenative to the modules presented above, you can perform your own analyses with BLIF 2.0. Therefore, you need to upload your favoured satellite data. For data research, visit http://www.earthexplorer.usgs.gov. After registration you’ll get full access to various kinds of remote sensing images.

In order to analyse spatial or temporal changes with BLIF, optical satellite systems are most appropriate. You can choose data acquired by Landsat missions (either Landsat 5, 7 or 8), which are broadly available at Earth Explorer. If you need a higher spatial resolution, also Rapideye-images can be used. Additionally, radar data (e.g. images acquired by the TerraSar-X satellite) can be implemented in BLIF.

A successful upload of satellite images requires specific file formats. Ensure that data has one oft he following formats: .tar.gz or .zip (packed).

4 Operating Principles

Because BLIF 2.0 is a web-based programme but no full software, it has limited options for analysis. The tools installed cover the major needs of remote sensing appreoaches. The most common issues and tasks can be performed. In contrast to BLIF version 1.1, the surface is designed more user-friendly and intuitive. Many tools contain detailed descriptions and further information, which are presented by an assistant. If you have any questions or recommendations, contact us: blif@gis-station.info.

To run BLIF, enter the programme by signing in at the registration area at (http://blif.de). You have different options of working with satellite data: choose a orefabricated issue or design your own one. More information about those possibilities is given in chapter 2.2. Decide upon data or picture sections to be processed. Afterwards, you can perform different tools of picture presentation and analysis. Optionally, an assistant guides you through the certain steps of investigating remote sensing images. In the following chapter, all of the tools available and further steps for processing are described in detail.

4.1 Registration and Sign-in

Via the homepage of BLIF 2.0 (https://blif.de) you can start the programme itself or get additional information on modules and contents. There is a collection of various kinds of satellite images in the gallery, which gives an overview on different approaches of remote sensing.

If you’d like to work with BLIF 2.0, you need to register first. Click on „Register“ and complete the data sheet. Afterwards a confirmation message will be send to your email adress. Your account is now activated. Attention! Note your username and password!

After registration you can sign in with your username and password at https://www.blif.de. As an official user, you have free access to lots of learning materials and satellite data.

4.1 Functions for Presentation and Analysis

The software BLIF 2.0 contains various tools for presentation and analysis of satellite data. Different kinds of editing tools can be accessed via the start screen. Firstly, change the language settings by clicking on the button on the upper right side of the screen. You can choose between German, English, Italian or French. The highlighted field ist he one that is chosen at the moment. You can always return tot he initial screen by clicking on the house symbol, which can be found next tot he language settings. Clicking on the red symbol in the upper right corner enables logout.

4.2.1 General Aspects of Handling

BLIF is intuitive in functionality and user surface. All tools and elements can be controlled by using mouse and keyboard. The table below explains the symbols and icons that are used most frequently, e.g. zooming. To select any function when working with the programme, press the left mouse button. Be careful! Because BLIF 2.0 is just a web-based programme, the right mouse button contains browser-specific functions. By scrolling you can either skip pages in the main menu or zoom continuously when processing image analysis.

Overview on some of the main functions

4.2.2 Choose Mode

You need to choose a mode before you start working with a satellite image. The difference between Beginner – Advanced - Professional and Full mode relies on the variety of tools for presentation and analysis. If you plan to work with (younger) students, it’s recommended to select a mode with a reduced range of tools.

The mode concepted for Beginners only includes tools for image cropping, contrast enhancement and producing colour images. You can test different band combinations for generation of false-colour images at most.

In contrast, the advanced mode contains some default indices, which improve the analysis options. Additionally, you can perform a manual classification. This leads to a thematic map that can be interpreted.

When working with the Professional mode, you can additionally compare an automated with a manual classification, as well as plot histograms of any single band.  These tools enable a more scientific evaluation of satellite data.

The tab „other“contains further options for selection of modi, which are designed for specific modules.

4.2.3 Choose your Assistant

In between the various steps of analysis, a digital assistent gives advice and provides background information. If you need help at any step oft he procedure, the assistant proposes a solution. You can choose between different assisting satellites, they only differ optically but have the same functionality. By the way, the graphical presentation is inspired by real earth observation satellites.

4.2.4 Choose Satellite data

After selection of operating mode and assistant, you start to work with satellite data. There are three different options to get access to satellite images, which are described below in detail. Firstly, you can utilize data, which is provided by others, and crop those. Secondly, you can choose between some prefabricated modules with already cropped images. Thirdly, upload your own data.

By clicking on „Back to Satellite Image“you can always return to the last image you worked at.

I. Choose satellite image: Selection of complete satellite images
You can choose your favoured data by clicking on „ Select a satellite image“. All of the objects have been designed for a specific topic (see list of topics), but you can use them for anything that can be observed in a certain area. You can either manually seek for satellite image by name („filter by name“) or by location („choose by world map”).

If you have decided upon the data, click on „Auswählen/Selection“on the right side oft he table to start analysing.

II. Select cropped image: List of prefabricated data

Here you can get access to all cropped images. All of them have been generated for a certain topic in context of learning modules. But the cropped data can be used for other issues as well. By selecting an image, you create a copy automatically. The original data is protected from being modified. Choose a tile by entering the name of a certain region or module. Start analyzing your favoured image by clicking on „Auswählen/Selection“on the right side oft he table.

III. Upload satellite image: Add your own data

As an alternative to the prefabricated satellite images, you can use own data that may be fitting better to a certain topic. Chapter 3.2 provides information on how to obtain data. Attention: the raw data hast o be unzipped, otherwise BLIF isn’t capable of displaying.
Start with clicking on the blue button and select the data you want to upload. In an additional window, you can choose the data from your workspace. Enter a short but detailed name (ideally containing the year of acquisition). Add the information on the satellite, which acquired the image. The upload starts after clicking on the right blue button („Upload“).

The level of progress (in percent) is displayed below the upload-button. After the upload has finished completely, an additional information report appears. Now you can go back to the home page and begin with analyzing. Your data is now available in the lists of all satellite images.

4.2.5 Analytical Tools

After deciding upon a satellite image tile, you can start processing the data. In order to have access to use the complete toolbox, the image needs tob e cropped. This is neccessary to reduce the time of precessing. Without cropping, solely colour composite images but no elaborate functions can be calculated.

Select area

By clicking on „Select Area“, a square-shaped window opens. At this point you can choose between two options for cropping the image. Either you move the square manually to your favoured position. Therefore, use the drag points for changing the size of the area and the hand button (drag+drop) for moving the box. Or you can enter numbers of pixel values or coordinates (degree of latitude and longitude) at the left hand side. Those mark the position of the edges, while the width (pixel) defines the size of the chosen area.

After choosing an area extent, you have to name the generated cropped image. Select a meaningful description. You can additionally save the image permamnently to BLIF by clicking on „provide for other users“, antering a name and “save”if you like to. After naming the window closes, your picture has already been saved. Go on by clicking on „crop“. Attention! Afterwards you can’t go back tot he original image! If you decide to change the area extent, click on „remove selection“in the left corner.

Contrast Enhancement

Satellite images sometimes have only little informative value due to changing acquisition conditions (e.g. daytime vs. Nighttime). In order to improve the image, contrast enhancement is often useful. Therefore, select the button “contrast enhancement” on the left hand side. Be careful! This is not only an optical improvement, you also change the original data by doing this!

You can perform the automated contrast enhancement for several times if needed. But avoid generating too extreme contrasts. Otherwise there will be problems with calssification of objects due to shadowing effects. In most cases, performing it once or twice is enough.

It’s important to remember that you change the original dataset by processing the contrast enhancement. In contrast to optical alterations (transparency, brightness …) you can’t go back tot he initial view by clicking on the undo button. To get back to the original data, select the button “reset channels” in the toolbox on the top row. Beware! You can do this step at any time of analysis, but all performed calculations will be deleted!

Histogram

Using the histogram allows you do perform a manual contrast enhancement. This relies on the distribution of values of each band. Decipe upon a certain band (e.g. red, infrared …) and press “Start“. Afterwards, an external window appears. It contains the frequency distribution oft he chosen band’s values. The total number of colour values is plotted against the intensity of a wavelength. By selecting an area in the diagram, you set the borders of wavelengths that will be displayed in the whole image. The thinner the chosen area, the higher the contrast oft he satellite image.

This procedure can be performed multiple times either for any single or all channels together. By clicking on „undo“you can go back tot he initial view. Press „okay“ if you want to keep a certain histogram stretching. Usually, histogram stretching prodices greyscale images. You can also generate colourful images by overlying with multiple colour composites.

Colour image

Generation of colour composites by using multispectral satellite data offers information that is not visible for human eyes. Using specific wavelength sections for image processing enables us to make heat, emission or reflection visible.

You can combine different spectral bands to highlight specific objects. Set your favoured channels for the RGB channels of visible light. Then press the “Start” button. To get true colour images, select the band combination Blue-Green-Red. The composite of NIR-Red-Green improves the identification of vegetation and land-use characteristics.  If you use IR-NIR-Grün, water or ice is detected best.  Combinations with using the Cirrus-channel is useful for displaying atmospheric processes. The thermal bands, that have a worse spatial resolution, are able to depict surface temperatures. Attention! Remind the right order of channels, which are used to generate a colour composite! It has to be the opposite of the RGB colour space. More information on this topic is given by the assistant.

Index

First, you have to decide upon one oft he given indices. Remind of what topic you’re working at and which outcomes you look forward to gain. Afterwards, press the “Start”-button.

Remind that images generated by index calculation usually contain pixel values from +1 to -1. BLIF automatically converts them to a colour ramp in the RGB colour space.

Images based on indices are automatically calculated channel combinations, that were designed for detecting cpecific object classes. Using the NDVI (Normalized Difference Vegetation Index) enables a detailed classification of different types of vegetation. The NDVI is based on bands with NIR and Green wavelength. The RVI (Ratio-Vegetation-Index) is similar to the former, but calculates just the simple difference of bands NIR and Red. In contrast, the index NDSI (Normalized Difference Snow Index) can be performed for analysing mountain areas. It relies on bands of IR and green wavelength and supports the distinction of clouds and snow.

Automated Classification

By using an automated classification, the program builds up clusters of similar pixel values. Those clusters describe classes, e.g. vegetation, water or populated areas. The number of classes, that will be calculated, controls the scattering in each oft he classes. The more classes, the better CAN the classification look like. But there is also the risk of becoming too complex if a large number of classes is generated.

Decide upon a useful number of classes. It’s recommended tot hink about a possible classification scheme before entering a definite number. What kind of objects do you want to group together? Which categories are possible to be distinguished from each other? Enter you favoured number of classes in the window on the left side and press „Start“. BlIF automatically performs he classification algorithm.  This can last up to a few minutes. After processing, a classification map appears in the main window. It’s important to know that you can‘´return tot he original data by „undo“. The classification map only represents an additional layer that an be deactivated on the right side oft he window.

Manual classification

In contrast tot he automated classification, you can decide upon the number of classes and the allocation of a specific pixel value. By setting „training areas“, the program defines a class based on reflection properties that are represented in a pixel value. The classification relies on how well those training areas can be seperated concerning their spectral characteristics. The better the training area, the better the resulting classification map.

To start with manual classification, click on „own classification“. In the appearing window, you can organize classes. Choose the best fitting colour for an object being displayed and name the created classes.

You can define training areas for each class by clicking on locations on the satellite image. You can therefore choose between lines, polygons or points. Select one from the categories mentioned above, they are presented as symbols at each class name. Alternatively, you can add coordinates of a certain object to define a class. Choose „enter coordinates“. Try to locate the training areas to the whole extent of the satellite image, this allows a more detailed classification result. If you mislocated a point, select „delete last point“. If you have enough training areas for a certain class, enter „ready“ and continue with the next category. Attention! Classification algorithms require high degreees of computing performance! Therefore, it’s important so save the training areas before starting the calculation.

The classification result consists of a map layer, as it is produced at an automated classification, but also a diagram of pixel values. You can proove the distribution of classes visually in the classification map or by checking the percentage of each class in the attached table.

Change Detection

Lots of remote sensing approaches aim to analyse land-use changes. Therefore, you can perform a change detection, where satellite images of the same area but different acquisition dates are compared. Select the button „Change detection“ at the end of a manual classification. You are invited to select another satellite images of the same location. Track the assistant’s hints and do the processing of a manual classification as it is descibed above.  When reaching the classification step, select „load training areas“. Now you can perform the classification of both images relying on the same training areas. This minimizes errors due to uncorrect allocation of pixels. Both classification maps will appear in an additional window. You can set values for transparency for one of them in ordner to compare both images. You can either compare the images visually or analyse the class statistics presented after clicking on  „show results“.

5 FAQ

• Select satellite by map

>>You can’t select a satellite image in the world map, if there’s another one on the same position but overlying the one you want to use<<

Because they have the same location, the images are displayed overlying each other. With using a right-click you can change the order oft he displayed images. Now you can select the other one.

• Load an image

>>You selected a satellite image but nothing is displayed <<

Sometimes BLIF has problems with automatically loading of images. If you just click on contrast enhancement or define any colour composite, the image will appear.

• Change layers

>>After performing the index calculation, you can’t go back tot he initial satellite image by clicking „undo“ <<

BLIF works like a pseudo-GIS, which means it creates seperate layers for some steps of analysis. You can decide the layers by clicking on the paper staple on the right side oft he window. Now you can choose the original dataset, or any generated map layer.