imagico has commented on the following diary entries

Post When Comment
DigitalGlobe Satellite Imagery Launch for OpenStreetMap 16 days ago

zoom levels: Yes, ideally all levels of course but practically adding z12 and z11 would already be good.

imagery offsets:

Most extreme case i remember was in the Lyngen Alps - around here:

Differences with the same image source can be found here:

Here i get ~50m difference even at sea level:

I know these are pretty nasty areas due to steep relief but i generally would expect at least no larger differences with the same image basis (i.e. the same viewing direction) unless you changed the relief data basis. Offset at sea level to me also indicates insufficient quality relief data.


Sorry i read over that part. Looking forward to it.

By the way i forgot to mention: Good to see you were able to keep the terms of use fairly plain and simple so you can actually read them without getting a headache.

DigitalGlobe Satellite Imagery Launch for OpenStreetMap 16 days ago

This is great news, thanks to DG and supporters for making this possible.

A quick look at the imagery indicates there is quite a lot of useful stuff in there - even if there is obviously a lot of overlap with imagery we already know from Bing and Mapbox there are also images were existing sources provide nothing of comparable resolution and furthermore there are many areas where having an additional, different image is useful for verification.

Two quick observations from looking over the new layers at a few places:

  • There seem to be quite severe alignment differences between the two layers and DG images from Bing and Mapbox, sometimes even with clearly the same image as basis but apparently processed differently, occasionally several hundred meters in magnitude - like for example in some parts of Norway.
  • The starting zoom level for the tiles with the images is fairly late (z13), especially for high latitudes. This makes using the images for finding gaps in mapping like looking for missing islands, lakes etc. quite difficult since you have to zoom in to get the image but then cannot see a larger area any more. So as a suggestion - if you could extend the tiles by a few zoom levels downwards that would be very useful. The imagery from Mapbox you have for z<13 and the Landsat Geocover fallback imagery is not really of use for mapping, it could even be preferable not to deliver tiles without DG images so the editor shows the image layer below instead.
  • There is currently no recording date metadata available - this would be extremely helpful for mapping. Bing has this and we have been bugging Mapbox to add it for years with no success.
  • Having coverage polygons indicating the image coverage would be great for image source selection as well of course.
OSMF regular member distribution 21 days ago

According to there were 396 normal members in November 2016 so if there were 485 in early January that is almost frightening.

OSMF regular member distribution 21 days ago

Wow, that means membership increased by nearly 100 members in half a year.

OSMF regular member distribution 22 days ago

I got the data from OSMF with the premise not to redistribute it and not to be too detailed when displaying it on a map so that single members cannot be inferred.

I don't think that was really more successful with you blurred style than it would have been with a more objective display method. All the feint isolated dots are clearly individual members. In your map you don't really get a good idea how many more members there are in Europe than in the US. It could easily be anywhere between three times and 30 times as many.

Maybe you could give us member numbers per country for the US, Canada and Europe.

OSMF regular member distribution 22 days ago

Thanks for the effort but providing the underlying data would probably be more useful.

Side note: it never ceases to amaze me how people think that blurring data somehow improves the value of an illustration. A simple dot density or proportional symbol map would be much less distorting. And of course an equal area map projection is generally considered a hard requirement for this kind of illustration as well.

Mapped in Every Country of the World 28 days ago

Well - customarily we in OSM do not give much about authoritative classifications - see also and the ambiguities listed there. The HDYC country list is a fairly consistent list of territories (although some of the boundaries used are off leading to quite a bit of stuff being classified as unknown).

Mapped in Every Country of the World 28 days ago

This is a fairly abstract exercise of course but you missed at least Greenland, Svalbard and Antarctica (assuming here of course you use the HDYC definition of 'country').

uMap "OSM 'Find-a-plane' " 30 days ago

Nice image.

Airplanes in imagery are a fairly common sight especially around large and much frequented airports of course. They tell you quite a lot of thing on how the image was taken. The one you showed was for example photographed by a satellite with a higher resolution panchromatic band and significantly lower resolution multispectral sensor with a linear resolution ratio of about 1:4 as typical for today's commercial high resolution satellites. This manifests in the sharp but colorless plane and several slightly offset blurred images of it in different colors.

For comparison here a typical image of a plane in lower resolution imagery without a separate panchromatic band:

People spamming diaries with irrelevant comments about 1 month ago

I understand the worries about spam but you should not blame the admins for that. They are all volunteers. If fighting spam requires additional resources (either in development or operations) you should not automatically assume this has to be provided by the admin team.

Also keep in mind as an outsider you usually only see the spam that is not dealt with while spam that is already dealt with is invisible to you. You do not know for example how many user accounts created by spammers are deleted. If you subscribe to the RSS feed for these diaries you will get to see quite a bit of diary entry spam but most of this is removed and not visible on the website after a short time.

People spamming diaries with irrelevant comments about 1 month ago

This is standard comment spam - everyone running a website with comment option is usually familiar with this problem.

Relevant links:

Are maproulette challenges undiscussed mechanical edits? about 1 month ago

Another short update: There has now been a user block put on the involved accounts by the DWG:

Editing activities in the meantime had continued mostly unchanged after the previous update (which is more selective than earlier but still often questionable regarding the whole approach). The Maproulette challenge is about half complete now with about half of the tasks done being marked as false positive.

Market shares of editors about 1 month ago

I always wonder how these numbers were going to change if you'd exclude imports. Obviously most imports these days are performed through JOSM so it seems likely that the dominance of JOSM in terms of edits as well as the average changeset size of JOSM edits would drop significantly if you'd only look at normal edits. It would be interesting to know by how much though.

With just one data point in 2016 it is not really possible to say much about the effects of based on this probably.

Possibly importing USGS forest data about 1 month ago

@SK53 - yes, illumination differences are one of the biggest problems when doing such analysis. On Tierra del Fuego the mentioned data set has a lot of gaps (obviously considering the prevalence of clouds) and overestimates tree cover - the Hermite Islands for example are depicted with at least about 30-40 percent tree cover.

Possibly importing USGS forest data about 1 month ago

A few notes on this data:

  • this data is not really new - research work this is based on is from 2013/2014 and the data was published more than a year ago IIRC.
  • this is not in any way suitable for import in OSM as is although you could consider deriving data from it that could be imported - which however is not a trivial task if you want good results.
  • data quality of this is fairly good considering the scope but not great. The methodology how they identify forest is complex and not fully documented. The difficulty here is to identify forests and differentiating them from other types of vegetation. Especially on a global level where you are dealing with a huge variety of ecosystems all with different spectral characteristics this is really hard. In principle this kind of data set usually depicts woody vegetation in general rather than forests/woods in a strict sense. Also note this is not meant as a data source for cartographic purposes but as a basis for detecting and analyzing changes in forest cover.

That being said if a local community is looking for a way to map forests in their area and considers importing or automated processes producing forest polygons using this data could - when done well - lead to more useful results better suitable for subsequent refinement and improvement by hand in OSM than data sources like Corine Land Cover which are inherently unsuited for OSM. None the less you should also keep in mind that locally you can usually do much better if you specifically identify forests on up-to-date open data imagery - either by hand or using automated processes because

  1. you can use local knowledge
  2. you would have a more recent and higher quality data basis.
  3. you can tune your forest detection specifically for the local situation.
Lets have changeset mentions about 2 months ago

Actually mapper mentions would be at least as useful but likely not really feasible due to the extreme abuse potential.

Note what you suggest, namely to automatically add a back-referencing changeset comment is much more obtrusive than the github feature which just silently adds a back-reference without a notification.

Are maproulette challenges undiscussed mechanical edits? about 2 months ago

A quick update: the challenge now has a more elaborate description:

This challenge consists of islands which have overly sharp angles or are over-simplified. Check all available imagery before editing the islands. Bing may be offset, so only fix a task if you have calibrated imagery of the area. Please skip tasks where imagery is not available. Please familiarize yourself with the proper alignment of coastlines, this information can be found on the OpenStreetMap Wiki.

This is not quite correct, tasks also exist for islands with fairly smooth outlines so their thresholds are fairly off but it explains how they produce their tasks.

And those working on the tasks now seem to be more selective in what they change, there are now nearly as many new tasks marked as false positive as there are as fixed.

Overall this is now mostly sad in terms of waste of ressources. All of these problems could have been avoided if they'd have discussed their plans beforehand. If half the tasks you look at turn out to be bogus that is just not very efficient.

So a policy for organized editing would not only be in the interest of OSM, it would also be in the interest of those organizing such edits. ;-)

Are maproulette challenges undiscussed mechanical edits? about 2 months ago

Editing has resumed, some of the changeset comments have been replied to, including the admission that this is an organized effort but still pretending this to be a normal group of regular OSM mappers and not telling who instructed and is paying them.

Are maproulette challenges undiscussed mechanical edits? about 2 months ago

Yes, agreed. And @mvexel already indicated he does not want Maproulette to be used for shadow mapping activity and i assume there will be changes to prevent such abuse in the future. And if there is further need for more thorough QA for the challenges posted there would be options for that too (like for example a grace period between publishing a challenge and it becoming available for mappers to work on which can be used for evaluation).

Are maproulette challenges undiscussed mechanical edits? about 2 months ago

I have my doubts if without a clear mandate in form of binding rules volunteer administrators can do much good here but of course Maproulette can introduce such rules independent of the OSM community as a whole and if they work well this might serve as a basis for developing a broader general policy.

In all fairness one other thing needs to be said - that a contributing factor for the problems of this challenge is that we still use totally unsuitable images for mapping from Bing and Mapbox in many parts of the world and editors do not even give a warning not to. This would be very easy with Bing (Capture date in the metadata is 1/1/1999-12/31/2003 or 1/1/1999-12/31/2014), somewhat more complicated with Mapbox. We cannot and should not forbid using these images but a clear warning to any mappers doing this from the editors would be a big advantage.