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GeoBoundary[g]

returns the boundary line of the geo region g.

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GeoBoundary

GeoBoundary[g]

returns the boundary line of the geo region g.

Details

Examples

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Basic Examples  (1)

The boundary of a geo disk is a geo circle with the same center and radius:

Wolfram Language code: disk = GeoDisk[Entity["City", {"Paris", "IleDeFrance", "France"}], Quantity[1000, "Kilometers"]];
Wolfram Language code: circle = GeoBoundary[disk]
Wolfram Language code: GeoGraphics[{disk, Red, circle}, GeoGridLines -> Automatic]

Scope  (7)

The boundary of a Polygon[GeoPosition[…]] object is a Line[GeoPosition[…]] object:

Wolfram Language code: pol = Entity["Country", "UnitedStates"]["Polygon"]
Wolfram Language code: GeoBoundary[pol]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

The boundary of a GeoPolygon object of a given path type is a GeoPath object of the same type:

Wolfram Language code: pol = GeoPolygon[{{0, 0}, {50, 20}, {10, 130}}, Automatic, "Loxodrome"];
Wolfram Language code: GeoBoundary[pol]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

The boundary of a GeoDisk object is a GeoCircle primitive:

Wolfram Language code: disk = GeoDisk[Here, Quantity[1000, "Miles"]]
Wolfram Language code: GeoBoundary[disk]

The boundary of a disk sector will have additional radial segments:

Wolfram Language code: sector = GeoDisk[Here, Quantity[1000, "Miles"], {-50, 30}]
Wolfram Language code: GeoBoundary[sector]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

The boundary of a GeoHemisphere region is a GeoHemisphereBoundary object:

Wolfram Language code: hemisphere = GeoHemisphere[Entity["City", {"RioDeJaneiro", "RioDeJaneiro", "Brazil"}]];
Wolfram Language code: GeoBoundary[hemisphere]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

The boundary of a GeoVisibleRegion primitive is a GeoVisibleRegionBoundary object:

Wolfram Language code: gvr = GeoVisibleRegion[Entity["Satellite", "25544"]["Position"]]
Wolfram Language code: GeoBoundary[gvr]
Wolfram Language code: GeoGraphics[{%%, Red, %}, GeoRange -> "World"]

The boundary of a DayHemisphere or a NightHemisphere object is a DayNightTerminator line:

Wolfram Language code: DayHemisphere[Today]
Wolfram Language code: GeoBoundary[%]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

The boundary of a GeoBoundsRegion object is a GeoBoundsRegionBoundary primitive:

Wolfram Language code: GeoBoundsRegion[Entity["Country", "China"]];
Wolfram Language code: GeoBoundary[%]
Wolfram Language code: GeoGraphics[{%%, Red, %}]

Properties & Relations  (1)

GeoBoundary[GeoGroup[{g1,g2,…}]] is given by the geo group of boundaries GeoGroup[{GeoBoundary[g1],GeoBoundary[g2],…}]:

Wolfram Language code: GeoBoundary[GeoGroup[{Polygon[GeoPosition[{{{43.349502921526, -1.78468798335306}, {43.3497985, -1.78445940000001}, {43.3653837, -1.77019340000001}, {43.3681162, -1.78639459999999}, {43.3730735, -1.7891532}, {43.3771217, -1.78792549999999}, {43.3779345, -1.78703680000001 ... 5464}, {41.9335435, 8.7471495}, {41.9082639, 8.71946959999999}, {41.9101849, 8.6421107}, {41.894162, 8.6085872}, {41.9350981, 8.62337150000001}, {41.9622323, 8.59062899999999}, {41.9776961, 8.66552020000001}, {42.0096144, 8.6563839}}}]], Polygon[GeoPosition[{{{50.754994663416, 6.02082622929586}, {50.7633567991225, 6.0183611623247}, {50.7741838609353, 6.02764327449245}, {50.7951777060937, 5.9799063511367}, {50.7980367067716, 5.9748624006479}, {50.8023526987829, 5.97574185131105}, ... 821}, {53.9289856927853, 14.2266821261543}, {53.9159162828827, 14.2076704513238}, {53.9140431832067, 14.1852409559837}, {53.9105962845935, 14.2056876898286}, {53.9003517985474, 14.2121966128828}, {53.8668706075425, 14.2120935793354}}}]], Polygon[GeoPosition[{{{45.9224464031654, 7.04419957737879}, {45.9225460115502, 7.04438238453911}, {45.9224654000104, 7.04450778935277}, {45.9133509165998, 7.06078795724687}, {45.9002287665667, 7.06418987722783}, {45.8952319956228, 7.07659165871427} ... 403, 8.22363969999999}, {39.1875155, 8.30962040000001}, {39.1443383, 8.3171627}}, {{36.7984641, 12.051308}, {36.7548795, 12.052027}, {36.7350588, 12.0043979}, {36.7680342, 11.956884}, {36.8163251, 11.9258571}, {36.839047, 11.9606946}}}]]}]]
Wolfram Language code: GeoGraphics[{GeoStyling[], %}, GeoBackground -> None]
Wolfram Research (2020), GeoBoundary, Wolfram Language function, https://reference.wolfram.com/language/ref/GeoBoundary.html.

Text

Wolfram Research (2020), GeoBoundary, Wolfram Language function, https://reference.wolfram.com/language/ref/GeoBoundary.html.

CMS

Wolfram Language. 2020. "GeoBoundary." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/GeoBoundary.html.

APA

Wolfram Language. (2020). GeoBoundary. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/GeoBoundary.html

BibTeX

@misc{reference.wolfram_2026_geoboundary, author="Wolfram Research", title="{GeoBoundary}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/GeoBoundary.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_geoboundary, organization={Wolfram Research}, title={GeoBoundary}, year={2020}, url={https://reference.wolfram.com/language/ref/GeoBoundary.html}, note=[Accessed: 13-June-2026]}