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

[Chris Hodges]

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?
>
> _______________________________________________
> Talk-GB mailing list
> Talk-GB at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-gb