Antarctica is quite a bit different from other continents due to the climate and the resulting abundance of ice. This page describes some of these differences and possible ways to represent them in OSM data.
Most of Antarctica is covered by ice up to the coast, therefore ice free areas are the exception rather than the rule. The ice free areas none the less need to be mapped. Because it is practically unfeasible to create a huge multipolygon for the antarctic ice sheet with tens of thousands of inner rings representing the ice free area it has been decided in 2013 that land areas south of 60 degree south - including islands (this line being the 'political border' of Antarctica and also a reasonable logical division) - are assumed to be covered by ice, i.e. are meant to be treated like natural=glacier.
Practically that means the land ice does not need to be mapped explicitly - though mappers can add natural=glacier for dedicated mapping of individual glaciers. Glaciers or ice streams within the ice sheet without verifiable boundaries can also be mapped with linear ways or nodes.
Ice free areas need to be explicitly mapped to be considered as such - practically that is mostly natural=bare_rock and natural=scree. This in particular also applies to ice free islands which - in addition to the coastline - need either a second way or a multipolygon relation with the coastline as member tagged natural=bare_rock. Otherwise they will be and should be interpreted to be ice covered.
Rather than having a huge multipolygon for the ice it might be a good idea to consider ice to be the default land cover for Antarctica and map the ice free areas individually as polygons (mostly natural=bare_rock, natural=scree). This would require support from the renderers. Individual glacial features could still be mapped (for example to name glaciers) by drawing them like elsewhere above the default ice.
The ice shelves around Antarctica are thick plates of ice (thickness of 100m and more) which exist at 44 percent of the antarctic coast. More details can be found on Wikipedia. How exactly this looks like in principle and where the various lines talked about in the following are can be seen in the image on the right.
Consensus in OpenStreetMap is that the coastline is to be mapped at the outer edge of the ice shelves (the calving line) even though the ice shelves are floating on sea water. We do that because this is the logical coastline with regards to human activities. Typical ocean use (i.e. ships) can only take place outside this line and typical land use (like buildings, airfields etc.) is fairly unrestricted on the ice shelf. Ice shelves are not simply thin floating ice, they are thick and stable over decades and more. Also see Sea ice below.
The ice shelves are represented as mutipolygons and are - corresponding to Proposed_features/Glaciers_tags - tagged glacier:type=shelf. Map rendering should best show them in a distinct way, different from normal glaciers.
In addition the outer edge (the calving line) and the inner edge (the grounding line) get different tags for the corresponding ways:
Sea ice is relatively thin, much thinner as the ice shelf and it is seasonal, so it changes with the time of year. Around the North Pole you have only sea ice, but not ice shelf. Sea ice is not mapped at all in OSM because it changes all the time.
Antarctica islands are called islands no matter if they are in the free ocean or enclosed in ice shelf. Their perimeter (ie the way) should be tagged as place=island in both cases (in case of islands enclosed in the ice shelf the edge would be the grounding line). If and only if they are in open water they are also tagged with natural=coastline. Like with all islands a node with place=island and a name can be put in the middle of the island.
Long straight lines are problematic in OSM everywhere. The earth is round and depending on the projection used for a map those straight lines should sometimes be rendered as curves. But the computer doesn't know that and will still just render a straight line between the two end points. This problem is not specific to Antarctica, but it is seen there more often than in other places, because map distortions are often greater and because features are often drawn with less detail than in other places in the world.
To mitigate this problem you should split up long straight lines every 100km or so with extra nodes.
Many natural features in Antarctica have multilingual names. In addition to language-specific name tags, an emerging convention is to assign the main name=* tag according to the language of the nearest permanent station. This seems generally avoided for elements that are far from any station by land or sea. It may be sensible to do this only for features easily accessible from the station by land or water that are relevant to frequent station operations, and treat more distant features as shared, preferring the name in the most internationally recognized language.
Sometimes the same element has more than one name in different countries that use the same language, like Argentina and Chile. To avoid adding multiple disputed names, it is sensible to assign the main name for a language according to the country of the nearest permanent research station that uses that language, adding the other name to the language-specific alt_name=* tag. If both are considered to be the main name in the two countries, and the feature is not next to a station in either country, it is sensible to assign both names as the main name in their language separated by a slash sorted alphabetically, as is often done for multilingual names on country borders.
Settlements and outposts
population=* refers to the permanent population of a settlement or, by analogy, to the occupancy of a year-round , implying that summer-only facilities could be, at most, place=locality. A likely more useful distinction that closely respects OSM definitions is as follows:
- place=locality for with no permanent structures (most field camps)
- place=isolated_dwelling for summer-only stations and field camps with permanent structures (most summer-only stations)
- place=hamlet;village;town for year-round stations
- place=hamlet for smaller year-round stations (most permanent stations)
- place=town for only as it is much larger than any other station in the whole continent
- place=village for the two civilian settlements of and and other year-round stations with similar occupancy and facilities: , and
- place=neighbourhood for contiguous settlements of the same country: and at Villa Las Estrellas, at Fortín Sargento Cabral; though historically the bases came first and are better known, this assumes that the civilian settlements are the main entity representing the settlement complexes, as it is the usual for urban settlements in most countries
Outposts that are still standing and temporarily inactive/closed with uncertain future may be mapped with disused=yes or abandoned=yes. An outpost known to be used intermittently should be considered active.
Roads and routes
Although many roads in Antarctica are covered in ice or snow, few meet the criteria for ice_road=yes. Use this tag only for roads that disappear during the summer due to melting, and for roads on ice shelves, such as the South Pole Traverse, which is on the Ross Ice Shelf.
Based on highway tagging assumptions, a balanced assignment could be as follows:
- highway=trunk to the connecting McMurdo to Amundsen-Scott, as it is the only traverse marked by flags, and it is more intensively maintained than the other long distance routes.
- highway=primary to routes between stations far apart; for example, regular supply traverse routes to stations far from the coast:
- (Dumont d'Urville to Concordia)
- (Zhongshan to Kunlun)
- (Neumayer III to Kohnen)
- Routes between nearby major stations, except when ice_road=yes (the combination does not occur near the Arctic where the vast majority of these roads are); for example:
- Visible or marked routes to major airports and harbours; for example:
- Williams Field Road (McMurdo to Williams Field)
- Phoenix Road (McMurdo to Phoenix Airfield)
- Frei, Great Wall, Artigas to Teniente R. Marsh Airport
- Zucchelli to Boulder Clay Runway, Enigma Lake Skiway, Zucchelli Ice Runway
- Flyplassveien (Troll Station to Troll Airfield)
- ice_road=yes routes between stations or major airports and harbours; for example:
- Routes to field stations, camps and minor stations (very small stations relatively close to much larger stations)
- The main ways within stations
- highway=unclassified to routes to huts and similar structures near the stations that are part of their complex
- highway=residential to the local ways within stations
McMurdo Station has few named ways, and its building numbers are unique within the station and refer to it, not the ways. For correct rendering and geocoding, use addr:housenumber=* + addr:place=McMurdo Station.
There are certainly further features which are rare or non-existent on other continents. The above are only the large scale phenomena that will be important for the import. Feel free to add other things here to help develop uniform standards for mapping.
Penguin colonies are often featured on official maps. They can be mapped using natural=birds_nest + birds_nest=penguin + nest_platform=no. The same scheme may be used for other bird species, for example, birds_nest=southern_giant_petrel.