[Talk-GB] Gathering street level imagery off road?

[Jon Pennycook]

I take action camera footage and upload it to Mapillary. I used to have a
mobile phone mount but it snapped after going over a pothole - avoid
plastic!

I record footage using my Cycliq Fly12 CE handlebar camera (I have also
used OLFI ONE.FIVE Black, Crosstour CT9900, and Cycliq Fly6 CE GEN 2 - two
helmet cameras and one rear camera - from time to time). For GPS, I use
Locus Map set to record every 2 yards or 0 seconds, recording only when
moving. To sync the camera and GPS, I record 10s of https://time.gov/
whenever I start recording and periodically (every 2 hours or so) after
that - the UTC time is what I need. Direction is not important as it will
be interpolated between two images.

Finally, I use a set of PowerShell scripts that I wrote to crop the
timestamp from the videos, then convert them to geotagged images, and
finally upload them to Mapillary (the scripts use exiftool, ffmpeg, and
mapillary-tools). Before uploading, I check that the images have the
correct position (if not, I tweak the offset between image time and GPS)
and delete rubbish images (including footage of me recording my phone
showing time.gov)

Scripts here: https://gitlab.com/jpennycook/bikecam
I use PowerShell 7 on Windows 10, but I expect it would work with
PowerShell 5.

Jon




On Thu, 24 Jun 2021, 11:33 Chris Hodges, <chris at c-hodges.co.uk> wrote:

> I've seen a high mounted setup for a bike but really wouldn't fancy it:
> https://www.openstreetmap.org/user/tordans/diary/395215 (probably
> spotted via the weekly OSM newsletter).  That's for a GoPro with GPS.
>
> Personally on a bike I'd go for a standard handlebar mount - there are
> some cheap all-metal ones on ebay that don't block the camera.  I use a
> waterproof phone with a lanyard attached to the bike as well, as I've
> killed a phone by dropping it off the bars too many times. Then either
> mapillary/KartaView's own app or timelapse software with geotagging
> (e.g. rolling my own using Tasker, which is running a script as I ride
> anyway).  I've looked into doing this myself but I navigate on my phone
> when I go anywhere interesting and the angle I need to see the screen is
> wrong for taking pictures.  I don't currently have a spare phone to test
> otherwise I might try again.
>
> The other option I considered is using timelapse mode on a
> handlebar-mounted action camera, synchronising its clock to my phone,
> and using the image timestamp to extract the coordinates from a GPX file
> recorded by the phone.  Mapillary says there are tools to combine the
> data sources
> https://help.mapillary.com/hc/en-us/articles/115001717829-Geotagging-images
> but anyway it wouldn't be hard using Python with libraries to handle the
> EXIF data and parse the GPX.
>
> One slight downside is 1s resolution but even going downhill on a bike
> that's not going to be more than about 10-15m so only a little worse
> than the GPS error.  Another is that geotagging for this purpose needs
> more than just a lat/long; it needs a direction (even if you have a 360°
> camera). That means more than simply grabbing a set of coordinates at
> the same time as the image was taken, instead using the neighbouring
> coordinates to figure out the direction of travel.  This then breaks
> down if you're travelling too slowly, when the random component of the
> GPS error becomes comparable to the distance between points (some of the
> error is correlated between fixes so it's not too bad, and you could
> always find the tangent to your track based on more points).  I'm not
> sure how sophisticated the tools linked by mapillary are for this.
>
> Vague ramblings I know, but hopefullly there are some useful hints, even
> if only at those links
>
> Chris
>
>
>
> On 24/06/2021 10:50, Mat Attlee wrote:
> > What's best practice for gathering street imagery off road ie foot
> > paths, forest trails etc? I've started using Karta View to capture
> > imagery during my run but wondered if there was a better way of doing
> > things.
> >
> > Also has anyone ever had much success using Karta View or Mapillary on
> > a bicycle mount - that is assuming such things exist?
> >
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>
>
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