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projfwd

Project latitude-longitude coordinates to x-y map coordinates

Description

example

[x,y] = projfwd(proj,lat,lon) transforms the latitude-longitude coordinates specified by lat and lon to the x and y map coordinates in the projected coordinate reference system specified by proj. Specify proj using a projcrs object (since R2020b), a map projection structure, or a GeoTIFF information structure.

Examples

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Project latitude-longitude coordinates to x-y coordinates by specifying a map projection. Then, display the projected coordinates on a map.

To do this, first specify the latitude and longitude coordinates of landmarks in Boston. Specify the coordinates in the NAD83 geographic CRS.

lat = [42.3604 42.3691 42.3469 42.3480 42.3612];
lon = [-71.0580 -71.0710 -71.0623 -71.0968 -71.0941];

Then, import a GeoTIFF image of Boston as an array and a map cells reference object. Get information about the map projection by querying the ProjectedCRS property of the reference object. Verify that the geographic CRS underlying the projected CRS is NAD83.

[A,R] = readgeoraster('boston.tif');
proj = R.ProjectedCRS;
proj.GeographicCRS.Name
ans = 
"NAD83"

Project the latitude-longitude coordinates to x-y coordinates using the same projected CRS as the GeoTIFF image.

[x,y] = projfwd(proj,lat,lon);

Display the GeoTIFF image and the projected coordinates on the same map. Change the marker symbol and color of the coordinates so they are more visible. Then, add axis labels.

mapshow(A,R)
mapshow(x,y,'DisplayType','point','Marker','o', ...
    'MarkerFaceColor','y','MarkerEdgeColor','none')
xlabel('x (survey feet)')
ylabel('y (survey feet)')

Input Arguments

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Map projection, specified as a projcrs object (since R2020b), a scalar map projection structure (mstruct), or a GeoTIFF information structure. For more information about map projection structures, see defaultm. For more information about GeoTIFF information structures, see geotiffinfo.

Data Types: struct

Geodetic latitudes, specified as a scalar value, vector, matrix, or N-D array, in units of degrees. The size of lat and lon must match.

Data Types: single | double

Geodetic longitudes, specified as a scalar value, vector, matrix, or N-D array, in units of degrees. The size of lat and lon must match.

Data Types: single | double

Output Arguments

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Projected x-coordinates, returned as a scalar value, vector, matrix, or N-D array.

Projected y-coordinates, returned as a scalar value, vector, matrix, or N-D array.

Tips

If the geographic CRS of lat and lon does not match the geographic CRS of proj, then the values of x and y may be inaccurate. When proj is a projcrs object, you can find its geographic CRS by querying its GeographicCRS property. For example, this code shows how to create a projcrs object from EPSG code 32610 and find the associated geographic CRS.

proj = projcrs(32610);
proj.GeographicCRS.Name
ans = 

    "WGS 84"
Introduced before R2006a