6.   Sets: connecting multiple images

This chapter of the tutorial introduces you to Bilko sets. Appropriately these can be recognised by the file extension .set.

Sets are Bilko's way of handling multiple images that are connected to each other in some way. Typically sets would be used to handle multi channel image data from sensors such as MERIS or AATSR. They can also be used to handle time series of observations from a particular region when all the images in the series have the same geographical boundaries and spatial resolution.

Sets are a vital component of the Bilko image processing system, which allows you to create colour composite images, animations, and spectral or time series analysis. They also make it possible to carry out mathematical calculations on image data using Bilko formula documents, or perform statistical analysis of image data.

Aim and objectives

This chapter shows how to work with multiple images by connecting them into a set. By the end of the chapter you should be able to

• use 'Open Connected' to load three dimensional image data (NetCDF, HDF, N1),
• produce a colour composite image from mult-channel data,
• understand what is meant by 'true' and 'false' colour composite images,
• use histograms and stretches to improve the appearance of colour composites,
• save colour composite displays for use in reports and documents outside Bilko,
• produce an animation from a time series of images,
• connect several images using the 'Connect' function of the 'Image' menu,
• save a number of connected images as a set for later use, and
• select a subregion from a set of images and saving this as a new set.

Chapter content

1. Opening multi-channel images - opening and displaying multi-channel data.
2. Creating a colour composite - assigning channels to red, green and blue.
3. Adjusting the display - using histograms and stretches to improve the.
4. Saving colour composites - how to save the display as a 24-bit (3x8-bit) image.
5. 'True' and 'false' composites - using composites to reveal relationships between channels outside the visible spectrum..
6. Time series animations - opening, connecting and animating time series data.
7. Saving sets - saving and storing linked images in Bilko.
8. Linked subsets - selecting and saving sub-areas as new sets.
9. Summary and conclusions - what you should have learnt in this section.

Images used in this chapter

The images for this lesson (below) are usually stored in the folder called tutorial_data Throughout the lesson you can use the links on the right sidebar to get information about them.

• MER_FR__1PNEPA20030915~.N1
  Meris Top of Atmosphere (Level 1B) data from Bay of Biscay, 15 Sept.2003.

• ATS_TOA_1COLRA20040201~.N1
  Level 1 scene from the Benguela region on the west coast of southern Africa recorded by AATSR on Envisat on 1st Feb.2004.

• ATS_DSST10_IO_03~.dat
  Monthly (level 3) sea surface temperature from the Indian Ocean recorded by AATSR in March, June, September and December 2003, and saved at 10 arcsecond spatial resolution.

• sst0_ats2_v00a.nc
  3-D NetCDF file of monthly averaged SST from July 1995 to May 2000, derived from measurements made by the AATSR instrument onboard ESA's ERS-2 satellite.