[gdal-dev] Re: Calibration in GDAL

[Andrey Kiselev]

Hi, Paul,

> I need a little education here. What is the use of the so-called
> calibrated raster? (I have always associated calibration to instruments).

And you are absolutely right.

GDAL supports importing data from the variety of sources, in particular from
the remote sensing data storage file formats. These data obtained by the
space or airborne based scanners and may be available for users with
different levels of processing. Information about calibration of the orbital
instruments (these coefficients determined dinamically on board) is received
with the data and stored in the output files passed to users. So for
satellite datasets we need a technique for extracting and applying
calibration information. Without calibration such data are not very useful
(if not to say more) and may be used as pretty pictures only (in case of
uncalibrated ASTER Level 1A data it is even not very pretty).

Even if you have data with high level of processing, like ASTER Level 1B and
Level 3 products, you still need to apply some function to actual values.
They are stored as integers and you should make floats from them. Of course
units of measurement also should be supplied with calibration function.

Calibration procedure is essential for any subsequent quantitative data
processing and exploration.


-- 
Andrey V. Kiselev
Scientific Research Center for Ecological Safety Russian Academy of Sciences
Office phone: +7 812 2307834 ICQ UIN 26871517
Registered Linux user number 169907

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