sunapi386's Blog – Page 9 – Hacker/scientist/entrepreneur.

Install QGIS Ubuntu 18.04

QGIS is a user friendly Open Source Geographic Information System (GIS).

sudo add-apt-repository ppa:ubuntugis/ppa
sudo apt install qgis

Typically this is needed when you do sudo make install after compiling some C++ code. I suppose you don’t need the -v verbose flag, because ldconfig - configure dynamic linker run-time bindings.

Transforming Lidar Point Clouds

I was playing with datasets and wanted to share with what beautiful visualizations but wrong map alignment looks like.

The different colors represent scans but merged improperly (not aligned).

Looks like a mess.

But overall the coloring is important with debugging what this data represents.

Here’s what it looks like all merged together properly.

Especially the truck

Lidar map merging is a difficult task, and merging the data takes quite some time. So it is better to sample parts of a large data set and see if the algorithm is doing the right job.

At least the lidar above were all in the same 2D plane.

Here’s what it looks like if they weren’t — a blob of mess.

**double** roll = rtkMessage.roll();
**double** pitch = rtkMessage.pitch();
**double** yaw = – rtkMessage.heading();

**double** roll = deg2rad(rtkMessage.roll());
**double** pitch = deg2rad(rtkMessage.pitch());
**double** yaw = deg2rad(rtkMessage.heading());

I tried a bunch of different methods and it turns out that I was using degrees in place of radians.

Here’s what after 5 days of working on this problem I finally solved

Here’s what the Google Maps view looks like

And here’s what the lidar point cloud data only looks like

Different view

Construction crane can be seen here.

Very interesting in the map stitch process!

Compiling PDAL

sudo apt install libgdal-dev
git clone https://github.com/PDAL/PDAL.git
cd PDAL
mkdir build
cd build
cmake ..
make -j
sudo make install

List cmake options with installing this GUI

sudo apt-get install cmake-curses-gui ccmake ..
ccmake ..

To get geowave plugin support, you need JDK. Geowave increases the project’s complexity so I’ll defer that to later, if I get to it.

sudo apt install openjdk-8-jdk

Never Again, BTRFS! NAS File System Rant.

I have a Synology DS918+ NAS running BTRFS. This is 2019 and development of BTRFS began in 2007. So it should be all good, right?

There are interesting features I wanted to try out. Mainly, keeping snapshots. I’ve also been using EXT3/EXT4, NTFS, HFS, APFS, FAT32, even reiserFS back in 2006-2010, so I’ve seen my share of file systems. I’m willing to try something new.

I’ve heard 2 of my friends complain about this file system, but decided to try it because Synology’s Setup UI made me inclined to think this is preferable.

I don’t know who the target audience for this web UI is, but recommending the BTRFS is a huge mistake. As a home user with a lot of pictures, it is just so unacceptably slow.

How slow is it?

I don’t have exact numbers, because they often time out. And I don’t want to go through the pain of waiting. I have about 16k jpeg files that in a flat folder. Simple operations are terribly slow.

Moving 100 files into a folder takes couple of minutes, because there is a copy made for each file moved.
Doing ls (list all files in folder) takes forever, my terminal hangs up and never returns even after hours.
- On the Synology Drive UI, it takes minutes, because the web UI is paginated, about 500 files listed per page.
Deleting files takes as long as moving them.
Defragging like 1995 is back, so you must remember to periodically “scrub” your disks, which take days (I have two 4TB drives).

I regret so much using this shitty BTRFS system. Unbelievable. RedHat abandoned using this for all the right reasons, it’s hopeless. I’ll be spending a weekend moving my data to USB disks and reformatting to EXT4.

Never again, BTRFS!