On Big Data and me

Beberapa tahun yang lalu, Saya mendengar pertama kali istilah “Big Data”. Kala itu istilah ini bagi saya masih terasa seperti jargon marketing, ‘buzzword’, ‘hype’, atau euforia yang membuat definisinya terdengar menarik namun maknanya sulit dipahami. Teknologi pada waktu itu juga memang sedang ramai-ramainya dengan media sosial dan mungkin awal dari revolusi penyampaian ide dari yang konyol sampai yang luar biasa (konyol, eh maksudnya) serius.

Sekarang mungkin masih banyak ekspresi yang terdengar hiperbola namun setidaknya potongan puzzle-nya sudah semakin jelas. Dalam bidang informatika, topik yang saya pelajari lebih banyak menitikberatkan pada proses algoritmik untuk menganalisis data yang pada dasarnya kompleks seperti multimedia (misal peta, gambar, dan video). Istilah ‘big data’ sendiri saya dengar pertama kali dari area yang lebih banyak penekanan pada data dan bagaimana penanganannya. Sekarang Saya cenderung memahami istilah big data sebagai sebuah konvergensi teknologi.

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GSoC 2013 so far : pre mid-term Evaluation

It’s been quite a while since my last post about Google Summer of code activities. I was trying to understand the inner working of the library which I use and gathering deeper knowledge about spatial coordinate and mapping. As I may previously mentioned in earlier post, I am working with GDAL and PROJ.4 Library. GDAL/OGR is mainly used for supporting many raster/vector format and also dealing with WKT (Well Known Text) representation of coordinate system. The Coordinate system is defined in WKT Format although in the GDAL/OGR Library, the main coordinate system transformation is done in the PROJ.4 library which is wrapped through an interface which consists of OGRSpatialReference and OGRCoordinateTransformation.
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Building PROJ.4 Library in Windows

First thing to do is to make sure all libraries are there. This is actually part of pre-application puzzle challenge. But then, the libraries are already in the github repo. This time, I would like to build it myself. just in case there will be another release during this project. I will only cover building under windows.

Using Visual Studio 2010
PROJ.4 usually come with autotools (autoconf and automake) but for VS, PROJ.4 comes with custom makefile (although no solution or VS project file). In order to build this library using visual studio, one can follow these steps:

  1. run cmd.exe as Administrator (this is important since my OS is 64-bit, otherwise it will generate errors with the debug informations)
  2. execute vcvars32.bat from visual studio directory (in my case it’s in VC\bin\vcvars32.bat)
  3. execute “nmake /f makefile.vc”
  4. if you want to install it then execute “nmake /f makefile.vc install-all”. It will then create a PROJ directory at C:\

Using MinGW/MSYS
I tried to build PROJ.4 by calling sh.exe from cmd but it was not seems to work and then I had to run from msys shell (by running msys.bat). BTW, I use latest MinGW distribution (using mingw-get). I guess these steps are similar with the steps to build a package in linux-based systems.

  1. open msys shell
  2. execute “./configure” from proj-x.y.z directory
  3. execute “./make”
  4. execute “./make install”

The whole building process is faster when using VS than MinGW even when configuring time is ignored. There is an issue though. At first, I was using “mingw32-make” command in which the build cannot be done. When i checked, the version of ‘mingw32-make’ is different with ‘make’. mingw32-make was mapped to later version (3.82.90 i686-pc-mingw32) while ‘make’ command was mapped to earlier version (3.81 i686-pc-msys).

Google Summer of Code 2013: Hello world!

Hello world! This is my first post about GSoC. I usually write post to this blog using Indonesian language so people who are from Indonesia can easily understand and also to contribute to probably technical corpora which is written in Indonesian. For the next posts that will be using gsoc2013 tag also will be written in English.

Now, a little bit of background won’t hurt.
This is my first experience in Google Summer of Code, applying and being accepted. My last status as student was 2010 which is almost three years ago. Now that I am back as student, I am eligible to apply as participant. Yay!

The project I am working on is under the organization of Computational Science and Engineering of Vienna University of Technology. Altough I am also a student in TU Wien, The Mentors are from different institute. My Mentors are from Department of Geodesy and Geoinformation. The project itself is implementing transformation algorithm for vertical datums. For me, this is something that is quite new. I did projects using spatial data before, but the inner working of the knowledge behind that was actually done by another person which background is geodesy. Well, the availability of libraries like PROJ.4, GDAL/OGR really helped me a lot back then. That’s why I thought this might be the way I can contribute back.
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(Another) attempt to volume (3d scalar field) data visualization

tampilan per slice yang dijajarkan

tampilan per slice yang dijajarkan

tampilan dengan voxel (kubus berwarna)

tampilan dengan voxel (kubus berwarna)

Kedua gambar di atas menggunakan data citra DICOM sebanyak 256 slice, per slicenya berukuran 256×256 piksel dengan bit per pikselnya 16. Kedua gambar memanfaatkan parameter tambahan yaitu nilai yang menjadi pembatas (threshold). Gambar pertama sebetulnya menyajikan tumpukan citra yang dijajarkan dengan tiap piksel yang nilainya di bawah batas akan dibuat transparan. Gambar kedua merepresentasikan tiap piksel sebagai sebuah kubus berwarna (voxel), hanya piksel yang nilainya di atas threshold yang digambar kubusnya. Awalnya cuma ingin membuat visualisasi dengan voxel karena proses yang ingin dilakukan adalah thinning untuk citra 3D (tulisan menyusul 😉 ) tapi jadi keterusan. Mohon maaf, kali ini cuma ingin majang gambar tanpa membagi kode :D. sekedar informasi, visualisasi di atas hanya menggunakan delphi 7 dan openGL native (tanpa shader, cuma display list).