[GIS] Identifying polygons that intersect with another polygon using ArcGIS Desktop

arcgis-desktopintersectionpolygon

I have two polygon layers, a vegetation layer and a treatment layer. I want to add a field to the attribute layer of the vegetation layer to indicate if any part of the polygon has been treated (overlaps with a treatment layer).

For the above example – I want an attribute table that ends up looking like

I do not want to intersect the two layers – I need to keep the full polygons in the vegetation layer, I just want to know if they've been treated. There are too many polygons to do this manually.

Best Answer

If you want to avoid using the Intersect tool, it seems you have two simple and quick options:

Select by location from the vegetation layer features that intersect the treatment layer. Then, use field calculator to change the isTreated attribute (when you use Field Calculator and you have features selected, it will calculate only for selected features).
Use spatial join with the vegetation layer as target layer and the treatment layer as join layer. Use a one-to-one relationship and choose to keep all target features. This will create a new polygon layer, with the exact same features as your original vegetation, and the features that intersected the treatment layer will have adopted attributes from the treatment layer. You can then use Field Calculator similarly, for the isTreated Field.

Related Solutions

[GIS] determining what polygons intersect another layer

You can use the intersect tool in QGIS or ArcGIS to create a new layer with the attributes of both polygons.

In QGIS>Vector Menu> Geoprocessing Tools> Intersect from there select the appropriate layers and determine where to save the data. In QGIS once the process is complete you will have to manually add the data where you saved it.

In ArcMap Geoprocessing Menu> Intersect

In ArcMap> ArcToolbox> Analysis Tools> Overlay> Intersect

Multipolygon vs Polygon Features for Large Intersect Operations in PostGIS

You are right that dumping the multipolygons to polygons makes the index more efficient, for the reason you mention.

So if the size of the dataset makes performance an issue you should:

dump the multipolygons into a new table.
create a spatial index on the polygons
get the intersecting part and restrict the query to polygons theat intersect.

Something like:

/*Create polygon table from multipolygons*/
Create table forest_polygons as select (st_dump(geom)).geom geom from forest_table;

/*create the spatial index*/
create index idx_forest_geom on forest_polygons using gist(geom);

/*tell the planner about the index*/
analyze forest_polygons;

/*Make a selection of forest in the municipality, or more correct:
Asign municipalitiy id to the forests*/
Select st_intersection(gem), municipalities_id as forest_in_municipality from
forest_polygons inner join municipalities 
      on st_intersects(forest_polygons.geom, municipalities.geom);

Best Answer

Related Solutions

[GIS] determining what polygons intersect another layer

Multipolygon vs Polygon Features for Large Intersect Operations in PostGIS

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