Comparing 2 polygon shapefiles for differences [duplicate]

Question

I have 7 shapefiles, each representing a year, all containing lots of polygons (c. 500,000). My aim is to take any 2 of them and compare how they have changed in terms of size and shape of polygon. (i am willing to split into much smaller tiles of course)

Also, each polygon has an ID so I want to see over the years how the geometry has changed for a particular polygon.

I've tried quite a few tools, intersections, duplications etc etc but nothing seems to quite work (or simply produces errors)

any ideas?

Answer 1

The Symmetric Difference operation shows areas were polygons do not coincide. You'd want to do this operation between the original and modified feature classes.

Symmetrical difference in ArcGIS

Answer 2

I'd use the following approach with GDAL: Multiple input shapefiles for ogr2ogr sqlite spatial operations
In detail, considering only two different years for brevity (but they could be all the seven years all together, as well), I'd wrap the layers in a VRT file like this (e.g. data.vrt):

<OGRVRTDataSource>
    <OGRVRTlayer name="shp2012">
        <SrcDataSource>shp2012.shp</SrcDataSource>
        <SrcSQL dialect="sqlite">SELECT ID, ST_AREA(geometry) AS area2012, ST_LENGTH(geometry) AS peri2012, ST_LENGTH(geometry)/ST_AREA(geometry) AS para2012 FROM shp2012</SrcSQL>
    </OGRVRTlayer>
    <OGRVRTlayer name="shp2013">
        <SrcDataSource>shp2013.shp</SrcDataSource>
        <SrcSQL dialect="sqlite">SELECT ID, ST_AREA(geometry) AS area2013, ST_LENGTH(geometry) AS peri2013, ST_LENGTH(geometry)/ST_AREA(geometry) AS para2013 FROM shp2013</SrcSQL>
    </OGRVRTlayer>
</OGRVRTDataSource>

Area, perimeter and a very simple shape index, i.e. the perimeter-area ratio (PARA) are calculated in the SrcSQL subelement for each layer. Then, it's possible to calculate the deltas of area, perimeter and PARA between the two years and store the results in a DBF file:

ogr2ogr diff_2013_2012.dbf data.vrt -dialect sqlite -sql "SELECT *, area2013-area2012 AS delta_area, peri2013-peri2012 AS delta_peri, para2013-para2012 AS delta_para FROM shp2013, shp2012 WHERE shp2013.ID = shp2012.ID"

Finally, the result DBF file could be joined with the geometries of the year you like.

Note: In case we have to consider also the shifts or rotation of geometries, we could select also their bounding box (extent) WKT representation, i.e. AsWKT(Extent(geometry)), to be calculated in the VRT file. Finally, we have to check if WKT are the same or not within the ogr2ogr command. The idea is to provide a simple boolean field, e.g. DIFFERENT, which synthesize all the considered shape indices (and extent WKT, as well).