There has been quite a bit of fuzz in the OSM community recently (like here – warning: link goes to patronizing and broken web interface) because one of the image layers with semi-global coverage that had so far been widely used by mappers as a source for remote (armchair-) mapping has been turned off.
Calls for the authorities (in other words: the OSMF) to fix this were quick and the OSMF board seems to try persuading the image provider to restore the status quo ante. Sadly, however, the event seems to have not initiated any larger scale reflection within the OSM community on its dependency on proprietary data providers, which has increased significantly over the past years.
In wealthy parts of the world with active mapper communities local mappers have over the years invested significant work into collecting suitable local image sources (i.e. aerial images) and obtained permission to use those for mapping in OpenStreetMap from their providers. This not only applies to Europe and North America but also other parts of the world like Japan and parts of South America for example. This is an impressive achievement and highly useful for the practical work of mappers. And because all these image sources are independently produced and provided by different local image providers there is no problematic large scale dependency on a single image source because of that.
But this only applies to a rather limited part of the Earth land surface. For the rest OpenStreetMap currently largely depends on a single satellite image provider (Maxar) and image layers based on Maxar imagery provided by a small number of US Corporations (Microsoft/Bing, Esri, Mapbox and – until recently – Maxar itself). This problem is aggravated by the fact that it is in particular those parts of the world where no local aerial image sources are available where OSM currently lacks significantly in mappers with local knowledge and over-proportionally depends on remote mapping. In addition all of the listed image layers to varying extent have a focus on those parts of the world where other local image sources are available as well and elsewhere often have more patchy and lower quality coverage.
I have pointed out in the past that an important avenue for the OSM community to mitigate this dependency is to focus more on using open data satellite imagery. Even if this cannot fully replace commercial images, open data satellite imagery is currently severely underused in OSM, largely because of the lack of convenient practical availability of high quality images from such sources to mappers.
Of course there are other options the OSM community could try to decrease the current dependency on a single imagery provider:
- invest in recruiting mappers with local knowledge in larger parts of the globe (which would of course require the English speaking influential parts of the OSM community to open up more to true cultural diversity).
- invest in the capabilities of mappers to map in high quality in the absence of high spatial resolution imagery. It is quite remarkable how dependent even mappers with local knowledge mapping using on-the-ground surveying are often on image availability. Doing so would consist both in educating mappers in techniques that do not rely on high spatial resolution imagery and equipment that allows precision mapping independent of imagery.
- diversify the supply of commercial satellite imagery. In the resolution class of Maxar (0.5m GSD or better) there is only a single other provider at the moment (Airbus/CNES) but in the slightly lower resolution range (1m GSD or better) there are quite a few more. I am not aware of any initiative from the OSM community to organize access for mappers to imagery from any of these sources on a larger scale.
- lobbying for opening aerial imagery sources in parts of the world where this exists but is not available for mapping in OSM yet.
- invest in production of open data aerial imagery, in particular recorded by UAV.
- better availability of alternatives to optical imagery for mapping in OSM. There are various parts of the world where no very high resolution optical imagery is available for OSM but other open data sources are – like elevation data in polar regions.
Making open data imagery more accessible for mappers
I have tried with my OSM images for mapping over the last years to demonstrate how competent selection and high quality processing of open data satellite imagery can be useful for mapping in OpenStreetMap. I have added some more images of the Antarctic now, substantially reducing the gaps in coverage of ice free parts of the Antarctic.
I have chosen the Antarctic for this in particular because the proprietary higher resolution image layers tend to not have coverage there (or are very patchy). And also because of the high contrasts between ice and ice free areas the tone mapping used by many of the global image layers works poorly in these regions. Unfortunately, mappers in OSM seem to have a tendency to almost universally pick higher spatial resolution images over lower spatial resolution images, even if those are in all other aspects substantially worse (like more than ten years old with seasonal snow cover or poor processing). In other words: Larger scale use of open data satellite imagery in OSM is not only hampered by difficult access to such imagery in high quality, it is also made difficult by the lack of knowledge on the side of many armchair mappers for competent assessment and selection of the best image source for a specific mapping task.