Alex-7's diary

Recent diary entries

A tool to display Wikimedia Commons categories with coordinates on the OSM map

Posted by Alex-7 on 12 November 2018 in English (English)

This tool can display on the OSM map as geo-markers:

  • Wikipedia articles which have coordinates for all language versions of Wikipedia

  • wikidata, wikipedia, and wikimedia tags from the OSM map database

  • Wikidata items which have coordinates

And now I added the possibility to display also the Wikimedia Commons categories which have got the geographical coordinates.

The tool is available via this link:

I created it for my personal needs, for my surveys, but, perhaps, it could be useful to others.

The tool is as simple as it could possibly be. Just click on the map and the geo-markers will appear on the map up to 10 km around the click.

In areas with many categories it makes sense to reduce the radius of the search, because the maximum number of displayed categories I limited to 100.

P.S. Only categories which are connected to a Wikidata item or Wikipedia article are displayed. I do not know how to display absolutely all categories with coordinates via MediaWiki API, or if it is possible at all. On the other hand, the categories which are not shown are usually the sub-categories of those main ones which are displayed.

But it is possible to add the tag wikimedia_commons=Category:* to an OSM object, and then it will be displayed via search in the OSM database (the 2nd option).

Open Location Code, OLC, generator & search on the OSM map

Posted by Alex-7 on 15 October 2018 in English (English)

The OLC is supposed to become a kind of global address system. It is especially interesting for regions with obsolete or nonexistent on-the-ground addresses.

I wrote a simple Open Location Code generator & search on the OSM map:

To generate an OLC code just click on the map at a certain location. The search box or an URL link are to be used to find a location for an OLC code. For example, here is the location of the Norfolk Island Central School stadium:

The Google map supports the OLC too via its search box.

One of the great advantages of an OLC address is that it can point to an exact location of an apartment or an office in a large building, what potentially can save a lot of time and fuel, for example, for a delivery service vehicle, and by this reduce the CO2 emission.

This Wikipedia article about the [Open Location Code] ( provides detailed information on how the open source OLC system was created and how it works.

The successful test flight of the ultra-low cost DIY RC KFm2 flying wing with the GoPro camera

Posted by Alex-7 on 23 September 2018 in English (English)

I performed today successful test flights of my new twin engine puller (tractor) KFm2 RC flying wing with the GoPro Session 5 camera on board. KFm2 DIY flying wing

I wrote an article-report about it. There is a short, two minutes, video of the flight in the article.

The idea is to create an open source ultra-low cost aerial platform with excellent flying qualities which could be built DIY (Do It Yourself) from readily available materials for mapping, aerial photography, journalism, agriculture, etc.

There is also in the article another video of the detailed build of this air-frame.

My new multilingual web application "Travel Info Pack" to view hotels, museums, supermarkets, cafes, etc. on the map prominently

Posted by Alex-7 on 22 December 2017 in English (English)

The web app is multilingual. The language selection is in the upper right part of the page.

Basically, you can view the same information at the, but to use the Travel Info Pack one does not have to know neither SQL, nor English, nor OSM tags.

The list with the OSM tags (key=value pairs) is searchable as one types, and it is with the tags’s icons.

The web app memorizes the language choice, last location, and searched object. Each marker has got a link to view Wikimedia images with coordinates in the radius of 500 meters around the object.

Since the drop-down list is searchable, I can add much more OSM tags to it. It is what I plan to do.

Tool for measuring elevation above sea level on the OSM map

Posted by Alex-7 on 27 November 2017 in English (English)

I created a tool to calculate an elevation at the point of a click on the OSM map:

The elevation is calculated as an average from the values of the ele=* keys found around the click in the radius of 1 (or 2, or 3) kilometers.

I decided to write this simple application after I read an excellent article GPS Altitude vs Pressure Altitude.

For some areas of the world there is a lot of elevation data in the OSM database, and for some there is practically none. I think it is due to the misunderstanding about the difference between GPS Altitude and Pressure Altitude. The article makes it clear that both approaches are not perfect, but these are all what we’ve got, and we are to use one or another.

The application seems to be simple because all the heavy lifting is done by the Overpass API, OSM, and the Leaflet.

Elevation data could be useful for many purposes. For example, for planning a hiking or a cycling route, for planning a RPAS flight, for water management, etc. For example, if a hiking route starts at the altitude of 400 meters, and ends at 1600 meters, then it is immediately clear that it would be a hard day.

I also plan from now on to measure and add more ele=* data to the OSM.

Feedback and suggestions are very welcome.

Deep digital mapping

Posted by Alex-7 on 24 February 2017 in English (English)

Last weekend I went to map an archaeological site. I had read a couple of academic archeological papers on this excavation and knew the exact location of the site.

It is a Roman tiles, bricks and ceramic workshop near the town of Chancy which worked for eight hundred years, from 1st century BC till 7th century AD.

This archaeological site was excavated, and then it was covered with earth again for preservation. Still there are antique tiles everywhere around. At that epoch it was a hi-tech enterprise, a place where the Roman Empire was actually built. And it is not completely clear why it was closed after eight centuries of production (an interesting question for today’s reality too).

As a result:

I convert video to the open WEBM format, which is accepted by Wikimedia, with the command line tool ffmpeg. Some quality is always lost in conversion, but so far it is the best variant:

ffmpeg -i source.mp4 -c:v libvpx -crf 4 -b:v 18M -c:a libvorbis destination.webm

I used a free music with Creative Commons license for the video. But it is also possible to play yourself and record any music of any composer who died more than 70 years ago. For example, for these two videos I asked my spouse to play and record the musical themes:

Battle of Morgarten

The town of Zug

The idea of deep digital mapping is that reaching a remote destination takes time and effort. So being physically at the location allows not only to map an object on the OSM map, but also to film it, to record first hand impressions, perhaps to do some investigative journalism for a Wikipedia article, and link all this to the OSM map.

I realize by now that recording and editing a video is even more difficult than making good photos. Recording a musical theme is a world in itself too. It turns out that a digital piano does not record a MP3 file, but MIDI file (musical instrument digital interface), which should be exported to a computer first and then converted to an audio file with a program like the Logic Pro X.

If you have ideas or information on developing deep digital mapping, please, let me know.

Location: Le Cannelet, Geneva, 1285, Switzerland

Geolocations of Wikipedia articles on the OSM map

Posted by Alex-7 on 29 December 2015 in English (English)

I wrote a web-application to find Wikipedia articles geolocations on the OpenStreetMap

After the click on the map, it shows Wikipedia articles geolocations in the radius of ten kilometers around the click. A Wikipedia language can be changed by replacing the language code “en” for English, to “fr” for French, “de” for German, etc.

I wrote it mostly for myself (and actually use it), but it works for the whole world and for all Wikipedia languages. The number of articles is limited by 100.

The addressable map of Geneva, Switzerland, project

Posted by Alex-7 on 13 March 2013 in English (English)

Geneva is an international city. There are a lot of international organizations in the city: UN, UEFA, WTO, etc.

I am currently working on mapping Geneva with addresses. I use bicycle and [OSMpad] ( for iPhone 4S, and my own free time, mostly on Sundays.

If you want to join this project and do not know how then write me a message and I would provide some tips. To support the project visit my website [] (

It would take about two years in my estimation to mark all house numbers in Geneva.

Location: Champel, Geneva, 1206, Switzerland