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SpatialSymmetricDifference

Updated
globalmapper.SpatialSymmetricDifference(GM_LayerHandle_t32 aLayer1, GM_LayerHandle_t32 aLayer2, GM_SpatialOps_Params_t aParams) → GM_Error_t32

The Symmetrical Difference operation creates a new layer consisting of areas of the non-overlapping regions in the first and second input layers; overlapping regions are removed. In other words, it finds all regions exclusively in one layer OR the other, but not in both. Attributes for features in the new layer are copied from their original feature, from either the first or second input layer.

Parameters:

  • aLayer1 (GM_LayerHandle_t32) – First layer in operation

  • aLayer2 (GM_LayerHandle_t32) – Second layer in operation

  • aParams (GM_SpatialOps_Params_t) – Parameters

Returns:

Error Code

Return type:

GM_Error_t32


BEFORE

AFTER
../_images/Red_Blue_Circles.png ../_images/SymmetricDifferenceAfter.png

Example

The following is an example of SpatialSymmetricDifference.

import os
import globalmapper as gm

import_dir = "Z:/GM-20069/spatial_operations_sample_data/"
# Close all layers that may be open
layers_are_open = gm.GetLoadedLayerList()
if layers_are_open:
    arr_ptr, arr_size = layers_are_open
    initial_layers = gm.GM_LayerHandle_array_frompointer(arr_ptr)
    for i in range(arr_size):
        gm.CloseLayer(initial_layers[i])

err_LoadLayerList1, array_pointer, array_size_param = gm.LoadLayerList(
    os.path.join(import_dir, "LeftBlueCircle.shp"),
    gm.GM_LoadFlags_HideAllPrompts,
)
err_LoadLayerList2, array_pointer, array_size_param = gm.LoadLayerList(
    os.path.join(import_dir, "RightRedCircle.shp"),
    gm.GM_LoadFlags_HideAllPrompts,
)

# Get handle for the loaded layers
arr_ptr, arr_size = gm.GetLoadedLayerList()
layers_array = gm.GM_LayerHandle_array_frompointer(arr_ptr)
layers_list = gm.carray_to_list(layers_array, arr_size)

### START SAMPLE
spatial_params = gm.GM_SpatialOps_Params_t()
spatial_params.mResultLayerName = "SymmetricDifference_Result"
err_SpatialSymmetricDifference = gm.SpatialSymmetricDifference(
    layers_list[0], layers_list[1], spatial_params
)

### END SAMPLE

assert (
    gm.GM_Error_None == err_LoadLayerList1
), f"LoadLayerList1: Expected {gm.GM_Error_None}, got {err_LoadLayerList1}"
assert (
    gm.GM_Error_None == err_LoadLayerList2
), f"LoadLayerList2: Expected {gm.GM_Error_None}, got {err_LoadLayerList2}"
assert (
    gm.GM_Error_None == err_SpatialSymmetricDifference
), f"SpatialSymmetricDifference: Expected {gm.GM_Error_None}, got {err_SpatialSymmetricDifference}"

assert os.path.isdir(import_dir), f"Import directory doesn't exist: {import_dir}"
assert os.path.exists(
    os.path.join(import_dir, "LeftBlueCircle.shp")
), "Sample data doesn't exist"
assert os.path.exists(
    os.path.join(import_dir, "RightRedCircle.shp")
), "Sample data doesn't exist"