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From M.Eng. René Schwarz, Bremen/Merseburg
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Die deutsche Version meines Blogs finden Sie hier - manche Inhalte können sich zur englischen Version unterscheiden.
You can find an German version of my blog here − but some contents may be different to the English version.

An dieser Stelle können Sie alle aktuellen Blogbeiträge von mir einsehen. Aus zeitlichen Gründen komme ich nur unregelmäßig dazu, Blogbeiträge zu schreiben. Der Blog versteht sich daher als Gedanken- und Hinweissammlung.

Kommentare und Vorschläge in den einzelnen Beiträgen sind jederzeit gerne erwünscht.

DLR Pictures of the Year 2016

New Memorandum "Quaternions and Spatial Rotation" Released

Preview of Memorandum #6: Quaternions and Spatial Rotation

The Memorandum "Quaternions and Spatial Rotation" has been published as part of my Memorandum Series. It provides a compact introduction into quaternions and their application for spatial rotations:

  • brief introduction into quaternions, their components, notations, and properties
  • quaternion algebra formulary summarizing
    • basic properties (quaternion equality, hypercomplex conjugate, norm, and inverse)
    • basic operations (quaternion addition and subtraction, multiplication, division, normalization, cross and dot product)
    • exponential and logarithmic functions (quaternion exponential function, natural logarithm, logarithmic functions, power and root functions)
    • trigonometric and hyperbolic functions of quaternions
  • application of quaternions in the context of spatial rotations, quaternion rotation operators, rotations and transformations
  • conversion algorithms:
    • Euler Angles to Quaternion (for all 12 possible rotation sequences)
    • Quaternion to Euler Angles (for all 12 possible rotation sequences)
    • Direction Cosine Matrix (DCM) to Quaternion
    • Quaternion to Direction Cosine Matrix (DCM)
    • Euler Angles to Rotation Matrix (for all 12 possible rotation sequences)
  • time derivative of a rotation quaternion
  • quaternion interpolation algorithms
    • linear interpolation (LERP)
    • spherical linear interpolation (SLERP)

Have a look here if you are also interested into other Memoranda out of my Memorandum Series.

OpenPGP Key Transition

In the light of the recent occurences in the domain of computer security, I will hereby replace my old OpenPGP key by a new and stronger key. The old key is invalid with immediate effect and I recommend to use my new one for all future correspondence. Please see my key transition notice here for further details:


Using Moxa NPort 5450 Serial to IP Server with Linux Kernel Version 3.8.0 (tested with Ubuntu 13.04)

Unfortunately, Moxa's NPort Real TTY Driver for Linux is currently (version 1.18, released 2012/03/20) not compatible with Linux kernel 3.8.0. When I tried to install this driver for the NPort 5450 Serial to IP Server on my Ubuntu 13.04 machine (currently with kernel 3.8.0-27), the driver didn't compile. It turned out, that it is possible to patch the driver source code in order to get it work with Linux kernel 3.8.0 – here is a short documentation what I did.

New Memorandum on Astronomical Constants Released

In endeavor to extend my Memorandum Series, I published a new Memorandum on astrodynamical constants, listing commonly used constants in astrodynamics as well as in space science and engineering with their latest values according to recent publications. This Memorandum is going to be updated with new constants from time to time.

Have a look here if you are also interested into other Memoranda out of my Memorandum Series:


  • M004: Conversion between Gregorian and Julian Dates
  • M006: Quaternions and Spatial Rotation

Master's Thesis Available as Book and Download

Book cover

After one year of having missed to update the page on my Master's Thesis, I am finally pleased to announce the availability of my master's thesis „Development of an illumination simulation software for the Moon's surface: An approach to illumination direction estimation on pictures of solid planetary surfaces with a significant number of craters“ as book both in form of a free download (PDF file) and in form of a printed paperback copy over the book trade.

For details see this page.

php_mailparse.dll for PHP 5.4.x (VC9 version) available

I'm pleased to announce the immediate availability of a precompiled php_mailparse.dll for the PHP 5.4.x series, built with VC9. This version is compatible with the standard 32-bit binaries of PHP for Windows.

php_mailparse.dll for PHP 5.4.x is available for download here.

Please notice the instructions written here (they are valid for the new version too).

Breathtaking Time-Lapse Aurora Video in Norway 2012

Today I've seen this breathtaking time-lapse aurora video made in Norway, January 2012, by Christian Mülhauser. It is so fascinating, that it would be a shame not to share it with you.

Many thanks to Christian Mülhauser for his efforts!

Misleading Output of MySQL Profiling Feature

During the ongoing work on my Master's Thesis I noticed a bug in the MySQL profiling feature: The output of the SHOW PROFILE statement is misleading, since the presented durations are not given for the status in the same row, but the durations are given for the previous status!

New Video: Copernicus crater on the Moon during sundown (Moon's surface in 3D)

In this video you can observe the Copernicus crater on the Moon's surface during sundown. The simulation starts at 2011/12/15 00.00.00 UTC and will end on 2011/12/20 00.00.00 UTC.

This work was done within the scope of my master's thesis at the German Aerospace Center (DLR) and the Merseburg University of Applied Sciences. It is just a preliminary result, since the work on my thesis is ongoing.

Watch the video here: http://youtu.be/ItsRPdSf8Ks

More information about the video background/my master's thesis can be found here.

php_mailparse.dll for PHP 5.3.6 and above (VC9 version) available

I'm pleased to announce the availability of the precompiled php_mailparse.dll for PHP 5.3.6 and above, built with VC9. This version should now work with the lastest PHP binaries (tested with PHP 5.3.8).

PHP does no longer provide builds created with Visual Studio C++ 6 (VC6). Since PHP 5.3.6 you need a version of php_mailparse.dll compiled with VC9. So many people contacted me with the request for such a new version. Here it is!

php_mailparse.dll is available for download here.

Please notice the instructions written here (they are valid for the VC9 version too).

Generating a 3D topographic map of the Moon

3D model of the Moon's surface topography after meshing in MeshLab

In a short moment of stuffiness I read about NASA's Clementine Mission, which was launched in 1994. The Clementine spacecraft made several lunar observations, including a LIDAR (Laser Image Detection and Ranging) scan of the Moon's surface. The data of this LIDAR scan is available from NASA's Planetary Data System. I had the idea to generate a 3D model of the Moon's surface — this article shows the results.

Firefox 4 hangs during tab switching for several seconds

If you are experiencing problems with a hanging Firefox 4 after update to version 4.0.1 during tab switching, this line in your prefs.js (usually located at C:\Users\Username\AppData\Roaming\Mozilla\Firefox\Profiles\ProfileName in Windows 7) could be the reason:

Mysterious bug in PHP 5.3.5 crashes Apache in conjunction with MediaWiki 1.16.2

Today I encountered a mysterious bug in PHP 5.3.5 while using MediaWiki software. When I try to add following content to a MediaWiki page, Apache crashes and all websites hosted on the server are not reachable anymore:

LaTeX to SVG and PNG rendering class for MediaWiki

Some time ago I tried to print a page with LaTeX formulas of Wikipedia. The result was really ugly, because all LaTeX expressions in the MediaWiki software will be rendered to PNG images by default. Due to the nature of rasterized images, all scalings generate artifacts („Jaggies“). So a solution would be a vector image of the formulas.

Vector images in HTML is a hot topic today, because rasterized image file types (e.g. png, gif, jpg) are the most common in the web caused by the lack of browser support of vector images. SVG (Scalable Vector Graphics) are a really good thing, which is currently being implemented in all major browsers.

So I had the wish to render math within the MediaWiki software to an SVG image instead of an PNG image. Because all SVG implementations in the major browsers are experimental, a fallback solution is neccessary.

I have written a replacement for the original Math.php of MediaWiki, which works on Windows servers (I think it should even work on Linux systems, but at the moment I have no time to verify that), called the LaTeXSVG class. This class enables MediaWiki to render LaTeX formulas both to an PNG and an SVG image. This class automatically generates HTML code for the embedding of the SVG image with the fallback solution of an PNG image within a page.

php_mailparse.dll for PHP 5.3.x

I tried a long time to get a working binary version of the PECL extension (PECL: „PHP Extension Community Library“) mailparse for PHP 5.3.x in the Internet. As that failed, I tried to compile the searched *.dll file by myself. Unfortunately, the attempt took more time than planned. Therefore thanks to Иван Гущин, who compiled the php_mailparse.dll for PHP 5.3.x and wrote a documentation for the compilation in my order. The compiled php_mailparse.dll is published as public download.