I'm sure this must be really simple but i can't seem to find a way of doing this using FME.
I have a number of polygons representing building footprints and need to calculate the max, mean & mode for each using a DTM.
The only options i've found so far would be to either;
- turn my polygons into points at vertexes and apply the values to these
- do a centrepointreplacer and just use that - not ideal for large buildings / those on slopes
i'm sure there must be a simple way to achieve this.
Hi @jamiefinney,
I would clip the DEM using the footprints and transform the rasters per footprint into points (RasterCellCoercer) after that use the StatisticsCalculator with a group by per footprint to get the statistics you need.
Hope this helps.
Hi @jamiefinney, another approach. I would transform the DEM to a point cloud with the PointCloudCombiner, clip it by the footprint polygons, and then compute statistics with the PointCloudStatisticsCalculator. Optionally you can restore the footprint polygon geometries by applying a pair of GeometryExtractor and GeometryReplacer. The point cloud technology in FME is fantastic!
Hi @jamiefinney,
I would clip the DEM using the footprints and transform the rasters per footprint into points (RasterCellCoercer) after that use the StatisticsCalculator with a group by per footprint to get the statistics you need.
Hope this helps.
thanks wondered if that might be the method I needed. hoped there might just be a single transformer i could use.
Hi @jamiefinney, another approach. I would transform the DEM to a point cloud with the PointCloudCombiner, clip it by the footprint polygons, and then compute statistics with the PointCloudStatisticsCalculator. Optionally you can restore the footprint polygon geometries by applying a pair of GeometryExtractor and GeometryReplacer. The point cloud technology in FME is fantastic!
@takashi thanks for your reply as well thats an interesting method - i'll have to see how they compare speedwise.
I'm thinking along the same lines as Takashi, with some differences.
1) I clipped the raster and used the RasterBandMinMaxExtractor - although admittedly it only gets you the min and max, not the mean or mode.
2) Instead of a GeometryExtractor/GeometryReplacer you can simply calculate the results and then copy them back onto the original features using a FeatureMerger (assuming they have a common name/ID)
Something like this:
That would work whether you use raster or point clouds.
Anyway, you probably have it working by now, but I thought I'd add this info to the existing answers.
I'm thinking along the same lines as Takashi, with some differences.
1) I clipped the raster and used the RasterBandMinMaxExtractor - although admittedly it only gets you the min and max, not the mean or mode.
2) Instead of a GeometryExtractor/GeometryReplacer you can simply calculate the results and then copy them back onto the original features using a FeatureMerger (assuming they have a common name/ID)
Something like this:
That would work whether you use raster or point clouds.
Anyway, you probably have it working by now, but I thought I'd add this info to the existing answers.
I'm thinking along the same lines as Takashi, with some differences.
1) I clipped the raster and used the RasterBandMinMaxExtractor - although admittedly it only gets you the min and max, not the mean or mode.
2) Instead of a GeometryExtractor/GeometryReplacer you can simply calculate the results and then copy them back onto the original features using a FeatureMerger (assuming they have a common name/ID)
Something like this:
That would work whether you use raster or point clouds.
Anyway, you probably have it working by now, but I thought I'd add this info to the existing answers.
@itay, in my experiences, performance of the point cloud approach was better than the vector coercing approach in many similar cases. Try that!
@itay, in my experiences, performance of the point cloud approach was better than the vector coercing approach in many similar cases. Try that!