For capturing while riding with a bicycle the Getting Started Guide proposes to take photos every two seconds. My personal experience confirms this advice. A two seconds interval while riding at low speed results in a picture every 10 meters which allows to eliminate blurred or otherwise unusable photos without getting to big gaps between photos.
But what if all photos are good? Is it ok to upload long sequences of photos taken every 10 meters or would this overload the Mapillary servers? For me, such short distances seem ok for urban areas but highly redundant out of town.
Is there any guideline from behalf of Mapillary on this subject?
Hi @ray66 - thanks for your question, it’s a great one! Have no worries about the Mapillary server. We’ve been working hard to be able to scale up from the 125 million images that we have now to billions of images in the future.
In fact, the only limits to your capture frequency should be your device and its memory capabilities. For the purposes of great computer vision, it would be ideal to have about 5 m between the images. That’s why in our mobile apps we have now also introduced distance-based capture as the default setting, which is particularly great when you walk/bike, or drive at low speeds. In any case, feel free to capture with as high frequency as you possibly can, whether in time- or distance-based capture mode.
I waited for Katrin to answer before answering myself.
We do not have an insight in the costs of mly. My guideline : one picture every second.
Even when the pictures overlap and connect, my mapper may complain that he does not see or cannot read the needed information.
It not only depends on the surroundings and speed but also on the quality of your picture and the field of view. On a bike you must take the corners slowly when you have set a 1 second interval.
Walking, you might consider 2 seconds, but then you must take your turns very slowly. You could try the distance mode and use the extra shot button in the corners.
On a boat on a wide canal, I might use an interval up to 8 seconds.
How the distance mode works depends on your hardware. With me it works totally else when I use an external GPS receiver. Distance mode is not so good in the corners. When Galileo arrives we wil need a sideways-acceleration dependant distance. That’s why we should be able to switch to the time mode in a glitch.
I use 0.5 seconds interval when talking pictures sideways. I do not want to ruin mly either. I will redo the highways in the forward direction using the 0.5 seconds interval with a good camera and the sun from behind. This is not possible with my camera at this moment.
Reading the last interesting blog entry, I was also going to suggest 5 meters.
Thanks for your answers. Good to hear that there is no capacity problem on the servers. What keeps me from capturing with a 1 second interval or a 5m distance is the effort for post-processing the photos. My work-flow is: first delete blurry photos from the sequence, upload, adjust compass angles and finally edit blurs (still too much direction signs are blurred). This takes me much more time than capturing in the field. As Mapillary’s coverage is rather sparse where I capture, I prefer to privilege coverage over density and capture with 2s interval which results in 5 to 15m distance depending on speed.
I capture from my van.
On interstate highways going 70mph I notice, even though I have my capture set on 5 meters, I bet I go at least 50 meters between shots.
Of coarse the state, county and town roads have the most interesting data. I imagine on a bicycle you could do even better.
I am impressed with the amount mentioned of post capture work done on the sequences. I just up load two phone/cameras as one is capturing in order to avoid filling everything and having to stop wandering to upload.
With the three phone/cameras I have memory enough for just over 30,000 pictures. Capturing every 5 meters as I wander back unmapped roads, I need to free space up as I go along.
Here in hilly Kentucky I am finding even that hard with the limited cell coverage.
Some rainy day I’ll sit at my laptop and see what you folks are talking about with all this post capture processing. Today is a wonderful spring sunny day for capturing in an area no one has covered.
The only options offered by the app are 0m - 3m - 5m - 10m - 20m. I have been using 3m, but when slowly walking in dense inner cities this does not seem to be enough. However, 0m results on too many pictures. Could you please add some steps inbetween, e.g. 1m, 2m, or even a more finegrained (log scaled) slider?
distance-based capture is too reliant on gps, which doesn’t provide meter accuracy anyway. varying between 0-5m would be within phone gps error margins in a city
Yes and no… most likely the problem is the speed the camera can take images…
There isn’t a perfect answer I’m afraid… I’dd like the option “as fast as possible” and filter out doubles in post processing… but that’s not perfect also… (I did buy a better GPS unit, but still)…
My 2 cents: When around buildings, like a village or a city, around 2 to 3 meters is prefect (if your camera can handle it) on the highway i’dd say 10 to 20 meters is more then good enough…
when I check mappilarry images sometimes see the big forward flash for the next image in middle of image and sometimes I don’t. As I understood it depents of the distance between the images, how many meters is acceptable distance to see the forward flash?
I’ve faced the same issue in some sequences. In one of them, I set 10 meters, but I got like 100 meters between pictures. Image min delay was set to zero.
Because of this, I’ve changed settings in order to capture pictures every second. The problem is that sometimes I have to delete repeated images in places where I stop due to the traffic.
Am I doing something wrong or this is a known issue? Is there anything I can do in order to use the distance-based capture without getting too much space between pictures?
