You are not logged in.

#1 2021-11-11 06:47:18

cmoffroad
Member
Registered: 2021-07-15
Posts: 34

Recommending Maxar, Mapbox, ESRI over Bing for imagery surveys

Earlier this year, after running into multiple issues due to conflicting imagery, I did further research and found out that Bing imagery in Thailand is very outdated (around 2 years in urban areas, and up to 5+ years in rural areas), while other providers usually guarantee a 6 to 18 months window.

Bing provides an API that gives an estimate of how old imagery is for a specific area, so to demonstrate this,
I have built a small tool that compares Bing with Maxar, Esri, and Mapbox imagery: https://cmoffroad.github.io/osm-tools/aerial-imagery/
Simply jump to your location or scroll, zoom to any area of interest. Bing label will indicate how old is the imagery.

Samples:
    - Chiang Mai, Mae Kuang reservoir [Bing 2016]: https://cmoffroad.github.io/osm-tools/a … 5859590769
    - Bangkok, former Nang Loeng racecourse [Bing 2019]: https://cmoffroad.github.io/osm-tools/a … 7920846791
    - Phuket, new development [Bing 2018]: https://cmoffroad.github.io/osm-tools/a … 4491227269

I have also made the following addition in the wiki after exchanging with @nitinatsangsit and @AlaskaDave:

While Bing aerial imagery is available in many parts of the world and is the default layer in ID editor, it can be very outdated in rural areas of Thailand (often +5 years). 
A recommended alternative with more recent imagery is Maxar and ESRI.

However, I didn't use the proper workflow at the time and I should have brought the topic here first for discussion.
So if you have any change requests for the wiki, questions about the tool, please let me know.

Cheers,
Julien

Offline

#2 2021-11-11 18:00:49

Bernhard Hiller
Member
Registered: 2011-05-10
Posts: 1,074

Re: Recommending Maxar, Mapbox, ESRI over Bing for imagery surveys

Hm. I recommend to look for "new" features in the imagery, i.e. some new houses or new roads which do not exist in other imagery. Though old houses or roads could also be removed, and thus some older images deemed newer because of the additional features, that's rather untypical of Thailand, where old roads / houses just get abandoned.
But beyond new features, clouds can be an issue, and thus an older imagery can have advantages in some places over newer imagery.

Offline

#3 2021-11-12 11:31:43

AlaskaDave
Member
From: Homer, Alaska ; Chiang Mai
Registered: 2013-09-21
Posts: 457
Website

Re: Recommending Maxar, Mapbox, ESRI over Bing for imagery surveys

Wow!

That's an impressive piece of work. I've done the same thing, sort of but not as eloquently, by loading all these various imageries into JOSM and then viewing them individually to see which is best for the area I'm working in. I seldom bother with Mapbox satellite but in a random area I inspected with your tool just now, it was clearer than the others.

A big problem with ALL of the imagery is positioning it properly. Using GPS traces and adjusting the offset for each provider is the only way to reduce discrepancies but it is a nuisance. For one thing, other mappers might come along later and "correct" your objects' positions using a different imagery provider. I'm sure I've done that myself.

Keep up the good work. I'm glad you decided to stay around and I hope you keep on mapping.

Offline

#4 2021-11-24 10:25:50

cmoffroad
Member
Registered: 2021-07-15
Posts: 34

Re: Recommending Maxar, Mapbox, ESRI over Bing for imagery surveys

Bernhard Hiller wrote:

I recommend to look for "new" features in the imagery, i.e. some new houses or new roads which do not exist in other imagery. Though old houses or roads could also be removed, and thus some older images deemed newer because of the additional features, that's rather untypical of Thailand, where old roads / houses just get abandoned.

In most cases, yes, but at least in rural Chiang Mai it is actually quite common for:
- lands with existing structures to be razed for new housing developments
- farming huts and tracks to be abandoned or moved
- lake or riverbed tracks to disappear or be moved

In the Bangkok example above, most mappers will believe Bing has the most recent imagery while in fact, it's the oldest one.

AlaskaDave wrote:

That's an impressive piece of work. I've done the same thing, sort of but not as eloquently, by loading all these various imageries into JOSM and then viewing them individually to see which is best for the area I'm working in. I seldom bother with Mapbox satellite but in a random area I inspected with your tool just now, it was clearer than the others.

A big problem with ALL of the imagery is positioning it properly. Using GPS traces and adjusting the offset for each provider is the only way to reduce discrepancies but it is a nuisance. For one thing, other mappers might come along later and "correct" your objects' positions using a different imagery provider. I'm sure I've done that myself.

Thanks!! Very good point about the imagery positioning issue. This is something I sometimes struggle with, especially in mountainous areas where there is poor GPS accuracy. I still personally use Bing to find old forest tracks and this offset issue comes up often.

PS: I have added the ability to show OSM GPS traces in the tool as an extra layer.

Offline

Board footer

Powered by FluxBB