A Capture Workflow

This past weekend we captured some data for the upcoming Traffic Jam Session hackathon here in Malmö. Since the event is about hacking public transportation data, we mapped some of the local bus lines. We used six Android phones running the Mapillary app that captured a total of 50GB of photos.

alt devices The red things are TI Sensor Tags that recorded some additional data.

With this blog post I just wanted to share the workflow we used for this type of organized "large scale" capture session.

  • Meet up with all devices charged and plan who goes where. In our case we had coffee and waited for the rain to clear.
  • Turn off automatic syncing if you use Android.
  • Go out and capture. Depending on your mode of transportation, hold the phone in your hand, use a mount, whatever works in the situation. For vertical windows like a bus or tram, double-sided tape directly against the window works great.
  • Empty the phones at regular intervals. If you want to capture 10-20GB per device, you most likely will have to do it in several sessions and copy your photos over to a laptop.
    • On iOS you can do this in iTunes. Open the Apps tab and scroll down until you see the Mapillary app at the bottom. You can copy the photos from there.
    • On Android you can access the files over USB cable or if they are on an external SD card, you can put the card in a reader on your laptop.
  • Review the photos. When you are done capturing and have collected all photos it is much easier to go over thousands of photos on your laptop on a good screen. Just delete all photos you don't want.
  • Upload. The easiest way is to run our command line upload script. Just point it at the folder with all your photos and it should do the rest. If you cannot run the script, you can also copy photos back to the app and upload from there but that's a little messy. Don't worry about giving credit to the right photographer, all capture information is contained in the photo's EXIF. Anyone can upload a photo you took from anywhere, it will show as your upload.

The same process applies if you capture over long times with no WiFi to upload. Just copy the photos over to a laptop at regular intervals and review them in peace before bulk uploading.

Here's one of the routes. alt route

Here's a photo of Peter and a happy busdriver. alt devices

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