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SpatialDissolve

Updated
globalmapper.SpatialDissolve(GM_LayerHandle_t32 aLayer, GM_SpatialOps_Params_t aParams, float aSmoothing, GM_FeatureGrouping_t8 aGrouping, str aStr) → GM_Error_t32

The Dissolve spatial transform creates a new layer with a polygon that combines all overlapping or touching areas from aLayer into one new area. For example, if you dissolved a layer showing the US state borders, the resulting polygon would be the US national border.

The aGrouping parameter specifies whether all areas should be dissolved together, or just areas of equal attributes.

Parameters:

  • aLayer (GM_LayerHandle_t32) – Input layer

  • aParams (GM_SpatialOps_Params_t) – Parameters

  • aGrouping (GM_FeatureGrouping_t8) – Grouping type

  • aStr (str) – The attribute list string; may be an empty string

Returns:

Error Code

Return type:

GM_Error_t32


BEFORE

AFTER
../_images/Red_Blue_Circles.png ../_images/DissolveAfter.png

Example

The following is an example of SpatialDissolve.

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_LoadLayerList, array_pointer, array_size_param = gm.LoadLayerList(
    os.path.join(import_dir, "SingleLayerCircles.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 = "Dissolve_Result"
err_SpatialDissolve = gm.SpatialDissolve(
    layers_list[0], spatial_params, gm.GM_GroupingAll, ""
)

### END SAMPLE

assert (
    gm.GM_Error_None == err_LoadLayerList
), f"LoadLayerList: Expected {gm.GM_Error_None}, got {err_LoadLayerList}"
assert (
    gm.GM_Error_None == err_SpatialDissolve
), f"SpatialDissolve: Expected {gm.GM_Error_None}, got {err_SpatialDissolve}"

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