worldToDiscrete

Convert planar world coordinates to discrete subscripts

Syntax

[I,J] = worldToDiscrete(R,xWorld,yWorld)

Description

[I,J] = worldToDiscrete(R,xWorld,yWorld) calculates the discrete row and column subscripts I and J for the world coordinates xWorld and yWorld based on the relationship defined by the raster reference object R.

The interpretation of I and J depend on the RasterInterpretation property of R.

• 'cells' — I and J are the row and column subscripts of the raster cells or image pixels.

• 'postings' — I and J are the row and column subscripts of the nearest posting point sample.

Examples

Find Indices of Cell from World Coordinates

Import a GeoTIFF image [1] of Boston as an array and a MapCellsReference object. Find the indices of the cell containing data with world $\mathit{x}$- and $\mathit{y}$-coordinates of 776500 and 2956600 survey feet, respectively.

[Z,R] = readgeoraster('boston.tif');
[I,J] = worldToDiscrete(R,776500,2956600)

I = 1212

J = 3714

The result means that the cell center closest to the world coordinates is in row 1212 and column 3714 of the array.

[1] The data used in this example includes material copyrighted by GeoEye, all rights reserved.

Input Arguments

R — Raster reference

MapCellsReference object | MapPostingsReference object

Raster reference, specified as a MapCellsReference or MapPostingsReference object.

xWorld — x-coordinates in the world coordinate system

numeric array

x-coordinates in the world coordinate system, specified as a numeric array. The size of xWorld must match the size of yWorld.

Data Types: single | double

yWorld — y-coordinates in the world coordinate system

numeric array

y-coordinates in the world coordinate system, specified as a numeric array. The size of yWorld must match the size of xWorld.

Data Types: single | double

Output Arguments

I — Row indices

array of integers

Row indices, returned as an array of integers. I is the same size as yWorld.

For an m-by-n raster and world coordinates that are within the raster bounds, the values of I are in the range [1, m].

If the kth input coordinates (xWorld(k),yWorld(k)) fall outside the raster bounds in the world coordinate system, then the function sets the corresponding subscripts I(k) and J(k) to NaN values.

Data Types: double

J — Column indices

array of integers

Column indices, returned as an array of integers. J is the same size as xWorld.

For an m-by-n raster and world coordinates that are within the raster bounds, values of J are in the range [1, n].

If the kth input coordinates (xWorld(k),yWorld(k)) fall outside the raster bounds in the world coordinate system, then the function sets the corresponding subscripts I(k) and J(k) to NaN values.

Data Types: double

Version History

Introduced in R2013b