Bowen's Tech Blog
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This site has different types of tech blogs, including AR, CV, SLAM, Math, Coding and software developments. Each blog will be updated from time to time.

Index of main posts are as following.

More posts could be found in categories tab.

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Majority content of this post came from the book Basic Knowledge on Visual SLAM: From Theory to Practice.

SLAM (Simultaneous Localization and Mapping) is the technique to establish the nearby environment and localize the moving object inside it at the same time according to sensor measurements. SLAM can be used in augmented reality, autonomous vehicles, and robot’s navigation. The mathematic theory of SLAM is the state estimation.

Visual SLAM is a kind of SLAM that depends on on visual sensors (cameras), which also involves photometric and geometric computer vision.

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Check the IP of Raspberry Pi is very painful because the IP of the Raspberry Pi will change automatically after a period of time if you didn’t assign a static IP to it. Checking the IP of the Raspberry Pi requires the keyboard, monitor, and it requires time to check it.

One way to solve this problem is let the Raspberry Pi to automatically send its IP to somewhere, like Google Sheet. This can make life better. Following are the steps to achieve it.

Connect the Raspberry Pi with WiFi

You need to use keyboard and monitor to set up the Raspberry Pi’s WiFi firstly, also check the IP, because we need to use the scp command to send file to Raspberry Pi.

Use gspread to send IP to google sheet

Set up googld cloud project

  • Head to Google Developers Console and create a new project.
  • Press the Google API icon of this new project and press “Enable APIs and services”
  • Enable Google Drive and Google Sheets API
  • Press the credentials icon and press “create credentials” and select “service account key”. Press create to download a json file for credentials

Set up python file

  • Download the pi_logger.py from this link, edit it
  • Use scp command to send this file together the json file to the Raspberry Pi
  • Install the requested libraries which are included in the pi_logger.py file.
    • Note: You need to use sudo pip3 to install the libraries, otherwise it cannot be ran by bash later
  • Ran python3 pi_logger.py to test it. Go to your Google Sheet you should find a file created and shared by Raspberry Pi

Write a bash file to launch the python file

  • Create a bash file named launcher.sh
  • In the file, type sudo python3 /home/pi/%your path%/pi_logger.py, save it
  • Type sh /home/pi/%your path%/launcher.sh to test the code, it should have the same result.
    • Note: if the terminal said there is error when importing libraries, you just need to uninstall relevant libraries and use sudo pip3 to install it back

Automatcally run the bash file

  • In Pi’s terminal, type sudo crontab -e
  • Type */2 * * * * /home/pi/justdiedbot/launcher.sh >/home/pi/logs/cronlog.log 2>&1, which means the Raspberry Pi will send do the sending action every 2 minutes

Reference

[1] https://www.instructables.com/id/Raspberry-Pi-Launch-Python-script-on-startup/
[2] https://raspberrypi.stackexchange.com/questions/78141/python-script-fails-with-importerror-when-run-from-rc-local

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ARKit is a software framework for iOS to create AR applications. It support features of device tracking, plane detection, and could allow apps to place virtual objects on top of real-world environment.

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The SLAM algorithm based on traditional computer vision geometry and state estimation has been mature. There are lots of open source SLAM architecture, and different commercial products have their own implementation. Every SLAM implementation has its pros and cons. This post is to provide the high level guidance for how to design a practical SLAM system for products.

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