What the map shows

How built-up the Lake Balaton shoreline is. We counted a stretch as built-up where there is a building, harbour, pier, paved road, promenade or railway.

Development within 10 metres of the shoreline shows how extensive the direct waterfront development is.

Construction within 30 metres matters because, under current law, no new structure may be built within that distance.

According to the professional organisations supporting SOS Balaton, 100 metres is the desirable distance that should be kept from the shore.

Beyond the map, we also present the data on a straightened north and south shore, and we compiled a ranking of the municipalities by how built-up they are.

All data comes from OpenStreetMap (OSM).

Limitations

• The calculated figures reflect the current state of the map, so they are less accurate where OSM is incomplete.
• Few shore reinforcements, stone and concrete sea walls, quays, embankments and concreted waterfront promenades are tagged in OSM: along the Balaton shore there are only 31 retaining walls, 15 quays and 1 embankment (about 4.4 km together), and half of the footpaths do not tag their surface. In reality these may be much longer and more significant.
• Fences and walls are very incomplete in OSM, so we did not count them as development.
• The free-beach classification is based on OSM tags. Beaches without fee information may also include free beaches.
• The classification of harbours and piers is automatic and the 100 m pier-length threshold is arbitrary, so some smaller harbours may be missed, or a natural stretch may end up among the artificial ones.

Measurement

We divided the shoreline into 10-metre segments. For the point of each segment we calculated the distance to the nearest building, harbour, railway and paved road. The distance is measured in a straight line, in a circle around the point, not perpendicular to the shore: a segment counts as built-up within 10 m, for example, if there is such an object inside a circle of 10 m radius around its point. We cut the measurement off at 250 metres: “250” means that the nearest one is farther than that.

A segment counts as built-up if any of these is within the given distance. The three levels are: within 10 m (red), within 30 m (orange), within 100 m (yellow). A segment that has no building, road, railway or harbour within 100 m is unbuilt (green).

Roads

Only paved roads count as development. If the road has a surface tag in OSM, that decides: asphalt, concrete, paving stones, cobblestones and similar count; gravel, compacted gravel, soil, grass and sand do not. If there is no such tag, the road class decides: main roads, minor roads, residential streets, living streets and “unclassified” roads count; service roads without a tag and dirt tracks do not. Footways, cycleways and steps do not count as roads, except paved footpaths: we treat a highway=footway|path|pedestrian way as a road if its surface tag indicates a paved surface (asphalt, concrete, paving stones, cobblestones, paved), so concreted waterfront promenades are counted among the roads too, by their distance. We measured the distance to a road from the line of the road sampled every 3 metres. Railways count as development; on the map, railway sections within the 100 m band of the shore are shown as a faint grey line.

Buildings

For the distances we use buildings that appear in OSM with a building=* tag. On the map, buildings are drawn at their real size as squares. The “Exclude small beach buildings” switch removes buildings standing on beach areas that are smaller than 150 m² or of a small type (snack bar, toilet, cabin, shower block) from the map and from every figure.

Simplified shoreline, harbours and piers

The OSM shoreline of the lake, including the edges of harbours, piers and breakwaters, is 249.7 km. We follow the whole shoreline, including the edges of harbour basins and channels. Artificial structures projecting into the water (long piers, platforms built in front of the shore and ship-harbour piers, e.g. the Balatonfüred ship harbour) are not considered part of the shore: we leave out their edges (about 17.1 km in total). Such a projection is distinguished from a natural spit by the fact that even after a 40 m “closing” of the shore (morphological closing) it does not blend into the natural outline of the lake. In addition, we reviewed by hand the 38 protruding water bodies that OSM does not tag as harbours: we judged 15 to be harbours (their edge is a harbour section), 5 to be pier-like, fully concreted structures (their edge is left out of the shore) and 18 to be natural bays. A missing harbour at Fonyód was added by hand. For basins tagged as harbours, the whole shore of the basin is a harbour section (the edge of the water body around the basin that is separated from the lake by a large-radius “opening”), while the edges of the thin piers (narrower than 30 m) bounding the basin do not count as shore. Small jetties inside a harbour or marina (within 40 m of a counted harbour object, within 100 m of a marina mapped as a point, or in a basin tagged as a harbour) are parts of the harbour, not separate jetties. The edges of narrow piers and jetties (narrower than 30 m) drawn into the shoreline and projecting into the water do not count as shore either. Wherever the omission would have bridged the shore with a straight line longer than 30 m, we checked all 48 places one by one on satellite imagery: where the excluded edge was actually the shore of a harbour basin, bay or spit, we put it back into the shore (as a harbour in the case of a harbour), and we deleted the unnecessary connecting lines. At the base of an excluded pier, the two ends of the shore are joined with a straight line, so the shoreline is continuous around the lake. The shore used in the calculation is therefore 232.6 km. The omitted pier edges can be switched on in the All view, among the “Layers”.

On the other hand, any OSM object that is a marina (leisure=marina), a harbour (harbour=*, landuse=harbour, waterway=dock), a breakwater (man_made=breakwater) or a harbour ramp (leisure=slipway) counts as development, as do the retaining walls (barrier=retaining_wall), quays (man_made=quay) and embankments (embankment) tagged in OSM. These last three (sea wall, retaining wall, quay, embankment) count as development but not as a harbour: they do not appear in the Harbours view, and when you point at the spot they show up in the “Sea wall, retaining wall” row. A shore segment that lies on or next to such an object is coloured red, orange or yellow according to its real distance.

What we mean by pier and harbour: a pier is an object tagged man_made=pier in OSM. This is typically a jetty or pier that projects into the water perpendicular to the shore, but the tag does not prescribe the direction, so it may include built piers parallel to the shore. A breakwater (man_made=breakwater) is not a pier but belongs to the harbour category, together with the marina, the harbour and the ramp. A structure built on the shore or parallel to it that is not tagged with any of these in OSM is only part of the lake outline, so it does not count as a harbour or pier.

Of the piers (man_made=pier) only those at least 100 m long count. Shorter ones do not, because there are more than a thousand pier objects around the lake and most of them are small private and beach jetties (the median length is about 46 m). The 100 m threshold is arbitrary: it would include piers shorter than 150 m and longer than 60 m. Exception: a pier shorter than 100 m also counts if it is at most 20 m from a non-kayak harbour or marina (whether OSM mapped it as a point or as an area), or lies inside a marina area. We count and mark a harbour as a continuous stretch along the shoreline: harbour objects at most 15 m apart form one harbour, and the stretch of shore touched by the objects (at most 12 m away from it) is treated as harbour from the first to the last touched point, provided the touched points are at most 400 m apart. We only use objects tagged in OSM as a harbour, marina or long pier; piers and breakwaters that are not separately tagged in OSM do not count. Kayak harbours (with “kajak” in their name or tags) do not count. These stretches also count as 0 m distance in the measurement. The “Harbours” view shows the counted objects in grey (harbours, marinas, breakwaters, ramps, long piers and piers next to harbours), and how much of the shore (12%, 28.5 km) falls on them. The “Small jetties” view shows in white the other pier objects shorter than 100 m, i.e. those that are not inside a harbour or marina; these do not count as development, so only their number is shown.

There are 133 harbour objects around the lake in OSM: 25 drawn as areas and 108 as points (many of the latter are kayak harbours). As a check we compared them against web lists of harbours (welovebalaton.hu, predictwind.com): in every municipality named in the lists there is a harbour object in the data, except for the boat harbour of Balatonederics, which has only a jetty in OSM. The lists give no coordinates, so the comparison is at municipality level, not harbour by harbour.

A harbour/marina and a pier count not as a distance but as “present” or “absent”: a shore segment either has such a facility (within 10 m, which is the 0 m) or it does not. A shore segment farther than 10 m from a harbour therefore does not become built-up because of it. If a counted pier touches a shore sample point and there is a harbour or marina within 150 m, the two count as one facility, and the segment is “present” under both harbour and pier. The kilometre breakdown of harbours and piers follows this.

Beaches

The beach strip is built from the shapes of the OSM objects natural=beach and leisure=beach_resort|bathing_place|swimming_area: those 10 m shore segments that are on the beach area or at most 12 m from it (±25 m for beaches mapped as points). Free beach: a fee=no tag, or a name containing “szabadstrand”, “közstrand”, “szabad fürdő” or “ingyenes” (Hungarian words for free or public beach). Paid: fee=yes or any other fee value. Restricted: access=private|customers. Beaches without fee information are not shown. This is not an official list of beaches.

Reeds, marsh

The “Reeds” filter (in the second row) shows those 10 m shore segments that lie on, or at most 5 m from, an OSM natural=wetland area (reeds, marsh, wetland). It is a sign of natural shore and does not change the development figures. We only used areas mapped as closed lines; reeds are not mapped everywhere in OSM, so the value may be an underestimate.

North and south shore

The “Unrolled shore” view straightens the north and south shores into two horizontal bands, from west to east, at the real length of the shore. The split is based on the order in which the shore is traversed: the western cut is between Keszthely and Balatonszentgyörgy (at the mouth of the Zala), the eastern between Balatonvilágos and Balatonakarattya. Balatonvilágos belongs to the south shore. The north shore is 134.9 km long, the south shore 97.6 km (without the excluded pier edges).

How the map is drawn

The drawn lake surface is built from the OSM shorelines: gaps of at most 25 m between pieces of shoreline are joined, and then basins with a mouth narrower than 10 m are closed. Harbour basins and bays with a mouth wider than 10 m therefore appear as water, as part of the lake. This only affects the drawing; the measurement is made from the shore points.

After a municipality is selected, a faint dashed line on the map shows the active distance (10, 30 or 100 m) from the shore towards the land. The line is the edge of a theoretical band calculated from the measured shoreline: the measurement works in circles around every shore point, in a straight line, and the dashed line is the outer boundary of these circles. The line is only an informative drawing and does not influence the figures. On narrow spits, where the two shores are within 30–100 m of each other, the line may break or curve inward.

Figures

With the default setting (including small beach buildings), 23% of the shore (52.4 km) has development within 10 m, 46% (107.3 km) within 30 m and 79% (182.7 km) within 100 m. 21% of the shore (49.8 km) is unbuilt. Beaches cover 41.0 km of the shore (18%), harbours 28.5 km (12%).