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geocontourxy

Contour grid in local system with latitude-longitude results

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Syntax

[contourLines,contourPolygons] = geocontourxy(X,Y,Z,lat0,lon0,h0)
[___] = geocontourxy(___,Name,Value)

Description

[contourLines,contourPolygons] = geocontourxy(X,Y,Z,lat0,lon0,h0) returns line and polygon geoshapes containing contour lines and contour fill polygons, respectively. This function is non-graphical. You can plot the return values using geoshow, if desired.

example

[___] = geocontourxy(___,Name,Value) specifies name-value pairs that control aspects of the operation. Parameter names can be abbreviated and are case-insensitive.

Examples

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Open Live Script

Define a set of X and Y coordinates and create contour lines and contour polygons.

X = -150000:10000:150000;
Y =  0:10000:300000;
[xmesh, ymesh] = meshgrid(X/50000, (Y - 150000)/50000);
Z = 8 + peaks(xmesh, ymesh);
lat0 = dm2degrees([  21 18]);
lon0 = dm2degrees([-157 49]);
h0 = 300;
levels = 0:2:18;

[contourLines, contourPolygons] = geocontourxy(X,Y,Z,lat0,lon0,h0, ...
        'LevelList',levels,'XYRotation',120)
contourLines = 
 8x1 geoshape vector with properties:

 Collection properties:
        Geometry: 'line'
        Metadata: [1x1 struct]
 Vertex properties:
  (8 features concatenated with 7 delimiters)
        Latitude: [21.1171 21.0296 20.9819 20.9814 20.9880 21.0702 21.1122 21.1431 21.1671 21.1630 21.1171 NaN NaN 21.2852 21.2292 21.1388 21.0741 21.0435 20.9764 20.9704 20.9138 20.8759 20.8703 20.8578 20.8929 20.9872 20.9995 21.0984 ... ] (1x329 double)
       Longitude: [-158.5364 -158.5053 -158.4015 -158.3987 -158.3903 -158.3425 -158.3542 -158.3876 -158.4450 -158.5114 -158.5364 NaN NaN -158.6115 -158.6641 -158.6876 -158.6790 -158.6707 -158.6182 -158.6134 -158.5258 -158.4445 -158.4145 ... ] (1x329 double)
          Height: [769.9110 771.5545 686.9961 684.5002 672.2181 584.6248 578.2085 599.1402 650.4579 725.7670 769.9110 NaN NaN 833.2872 911.0870 965.8408 977.6917 979.9987 944.4115 941.7802 869.5591 807.3430 780.8316 705.1597 606.5604 ... ] (1x329 double)
 Feature properties:
    ContourLevel: [2 4 6 8 10 12 14 16]


contourPolygons = 
 9x1 geoshape vector with properties:

 Collection properties:
             Geometry: 'polygon'
             Metadata: [1x1 struct]
 Vertex properties:
  (9 features concatenated with 8 delimiters)
             Latitude: [21.1171 21.1630 21.1671 21.1431 21.1122 21.0702 20.9880 20.9814 20.9819 21.0296 21.1171 NaN 21.1171 21.0296 20.9819 20.9814 20.9880 21.0702 21.1122 21.1431 21.1671 21.1630 21.1171 NaN 21.2852 21.3001 21.3087 21.3269 ... ] (1x651 double)
            Longitude: [-158.5364 -158.5114 -158.4450 -158.3876 -158.3542 -158.3425 -158.3903 -158.3987 -158.4015 -158.5053 -158.5364 NaN -158.5364 -158.5053 -158.4015 -158.3987 -158.3903 -158.3425 -158.3542 -158.3876 -158.4450 -158.5114 ... ] (1x651 double)
               Height: [769.9110 725.7670 650.4579 599.1402 578.2085 584.6248 672.2181 684.5002 686.9961 771.5545 769.9110 NaN 769.9110 771.5545 686.9961 684.5002 672.2181 584.6248 578.2085 599.1402 650.4579 725.7670 769.9110 NaN 833.2872 ... ] (1x651 double)
 Feature properties:
    LowerContourLevel: [0 2 4 6 8 10 12 14 16]
    UpperContourLevel: [2 4 6 8 10 12 14 16 18]

Display Hawaii on a map, add a marker, and then display the polygons returned by geocontourxy on the map.

figure
usamap([18.5 22.5],[-161 -154])
hawaii = shaperead('usastatehi.shp', 'UseGeoCoords', true,...
        'Selector',{@(name) strcmpi(name,'Hawaii'), 'Name'});
geoshow(hawaii)
geoshow(lat0,lon0,'DisplayType','point','Marker','o',...
        'MarkerEdgeColor','k','MarkerFaceColor','k','MarkerSize',10)
 
cmap = parula(1 + length(levels));
for k = 1:length(contourPolygons)
      lat = contourPolygons(k).Latitude;
      lon = contourPolygons(k).Longitude;
      geoshow(lat,lon,'Display','polygon', ...
             'FaceColor',cmap(k,:),'FaceAlpha',0.5,'EdgeColor','none')
end
geoshow(contourLines.Latitude,contourLines.Longitude,'Color','black')

Figure contains an axes object. The hidden axes object contains 27 objects of type patch, line, text. One or more of the lines displays its values using only markers

Input Arguments

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X-component of a mesh that locates each element of Z in a local x-y plane, specified as a vector or matrix. geocontourxy assumes that units are meters unless you provide a Spheroid input, in which case the units of your input must match theLengthUnit property of the Spheroid object.

Data Types: single | double

Y-component of a mesh that locates each element of Z in a local x-y plane. specified as a vector or matrix. geocontourxy assumes that units are meters unless you provide a Spheroid input, in which case the units of your input must match theLengthUnit property of the Spheroid object.

Data Types: single | double

Data to be contoured, specified as a 2-D array.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Geodetic latitude of local origin (reference) point, specified as a scalar value in units of degrees.

Data Types: single | double

Geodetic longitude of local origin (reference) point, specified as a scalar value in units of degrees.

Data Types: single | double

Ellipsoidal height of local origin (reference) point, specified as a scalar value. geocontourxy assumes that units are meters unless you provide a Spheroid input, in which case the units of your input must match the unit specified in theLengthUnit property of the Spheroid object.

Data Types: single | double

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: [contourLines, contourPolygons] = geocontourxy(X,Y,Z,lat0,lon0,h0,'LevelList',levels,'XYRotation',120)

Contour levels, specified as a vector of Z-values. By default, the geocontourxy function chooses levels that span the range of values.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Rotation angle of the local x-y system, measured counterclockwise from the xEast-yNorth system, specified as a scalar value in units of degrees.

Data Types: single | double

Reference spheroid, specified as a referenceEllipsoid, oblateSpheroid, or referenceSphere object. Use the constructor for one of these three classes, or the wgs84Ellipsoid function, to construct a Mapping Toolbox spheroid object. (You cannot directly pass in to geocontourxy the name of your spheroid. Instead, pass that name to referenceEllipsoid or referenceSphere and use the resulting object.) By default, geocontourxy uses the WGS84 reference ellipsoid with units of meters.

Output Arguments

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Contour lines, returned as a line geoshape with one element per contour level. Latitude and Longitude properties contain contour line vertices in degrees. The contour level value of the k-th element is stored in the ContourLevel feature property of contourLines(k). A third vertex property, Height, contains the ellipsoidal height of each vertex. In combination with Latitude and Longitude, it completes the definition of the 3-D location of the contour line in the plane that contains the local origin and is parallel to the tangent plane at the origin latitude and longitude.

Contour polygons, returned as a polygon geoshape with one element (contour fill polygon) per contour interval. Latitude and Longitude properties contain the vertices of the contour fill polygons, specified in degrees. The LowerContourLevel and UpperContourLevel properties of contourPolygons(k) store the limits of the k-th contour interval. As in the case of lines, a third vertex property, Height, is included.

Version History

Introduced in R2016a

See Also

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