GeoTools correct use of ReprojectingFeatureCollection

Question

I have trouble understanding the use of the function ReprojectingFeatureCollection. Here is my code:

try {

    Double buffer = 500.0;
    String attributeBuffer = "";

    ReprojectingFeatureCollection clip_repojected = new ReprojectingFeatureCollection(clip, CRS.decode("EPSG:3857"));

    myBufferM buffered = new myBufferM();
    SimpleFeatureCollection bufferedFeatures = buffered.createBufferM(clip_repojected.collection(), buffer, attributeBuffer);

} catch (OperationNotFoundException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (FactoryRegistryException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (NoSuchAuthorityCodeException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (SchemaException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (FactoryException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

So my function gets a SimpleFeatureCollection as parameter and now tries to Reproject it to EPSG:3857. I have modified the gs:BufferFeatureCollection from the list of WPS processes of GeoServer and now call it myBufferM. I am trying to Buffer a FeatureCollection in meter instead of degrees (data's default unit). Previously I had the transformation to meter build into my Class myBufferM which worked good (transforming every feature geometry itself and then buffering it and reverse transforming it).

Now I am trying to transform the geometries beforehand using the Buffer function as it was before I modified it.

The question is: am I using the ReprojectingFeatureCollection correctly? Because the results I get now are wrong (in degrees).

If you need more code I will update my question. I have reduced it to the important parts. The total code would be kind of huge.

Answer 1

Your code as provided doesn't actually compile. I have no method collection in ReprojectingFeatureCollection. But using rfc.subCollection(Filter.INCLUDE).features() to create the iterator also works for me.

Here is how I would do this:

  public static void main(String[] args) throws IOException, NoSuchAuthorityCodeException, FactoryException {
    File inFile = new File("/home/ian/Data/states/states.shp");
    DataStore inputDataStore = DataStoreFinder.getDataStore(Collections.singletonMap("url", URLs.fileToUrl(inFile)));
    int limit = 10;
    System.out.println("original");
    try (SimpleFeatureIterator itr = inputDataStore.getFeatureSource("states").getFeatures().features()) {
      int count = 0;
      while (itr.hasNext() && (count++ < limit)) {
        SimpleFeature feature = itr.next();
        System.out.println(feature.getDefaultGeometry());
      }
    }
    String inputTypeName = inputDataStore.getTypeNames()[0];
    // SimpleFeatureType inputType = inputDataStore.getSchema(inputTypeName);
    // System.out.println(inputType.getCoordinateReferenceSystem());

    FeatureSource<SimpleFeatureType, SimpleFeature> source = inputDataStore.getFeatureSource(inputTypeName);

    FeatureCollection<SimpleFeatureType, SimpleFeature> inputFeatureCollection = source.getFeatures();
    ReprojectingFeatureCollection rfc = new ReprojectingFeatureCollection(inputFeatureCollection,
        CRS.decode("epsg:3857"));

    printer(rfc, limit);
  }

  /**
   * @param rfc
   */
  public static void printer(ReprojectingFeatureCollection rfc, int limit) {
    System.out.println("reprojected");
    try (SimpleFeatureIterator itr = rfc.subCollection(Filter.INCLUDE).features()) {
      int count = 0;
      while (itr.hasNext() && (count++) < limit) {
        SimpleFeature feature = itr.next();
        System.out.println(feature.getDefaultGeometry());
      }
    }
  }

which produces:

original
MULTIPOLYGON (((-88.071564 37.51099000000001, -88.087883 37.476273000000006, -88.311707 37.442852, -88.359177 37.40930899999999, -88.419853 37.420292, -88.467644 37.400757, -88.511322 37.296852, -88.501427 37.257782000000006, -88.450699 37.205669, -88.422516 37.156909999999996, -88.45047 37.098670999999996, -88.476799 37.072143999999994, -88.4907 37.06818, -88.517273 37.064769999999996, -88.559273 37.072815000000006, -88.61422 37.109047000000004, -88.68837 37.13540999999999, -88.739113 37.141182, -88.746506 37.152107, -88.863289 37.202194000000006, -88.932503 37.218407, -88.993172 37.22003599999999, -89.065033 37.185860000000005, -89.116821 37.112137000000004, -89.146347 37.093185000000005, -89.169548 37.064235999999994, -89.174332 37.025711, -89.150246 36.99844, -89.12986 36.988113, -89.193512 36.986771000000005, -89.210052 37.02897299999999, -89.237679 37.041732999999994, -89.264053 37.087124, -89.284233 37.091244, -89.303291 37.085384000000005, -89.3097 37.060908999999995, -89.264244 37.027733, -89.262001 37.008686, -89.282768 36.999207, -89.310982 37.009682, -89.38295 37.049212999999995, -89.37999 37.09908299999999, -89.423798 37.137203, -89.440521 37.165318, -89.468216 37.224266, -89.465309 37.253731, -89.489594 37.256001, -89.513885 37.276402000000004, -89.513885 37.304962, -89.50058 37.329441, -89.468742 37.339409, -89.435738 37.355717, -89.427574 37.411018, -89.453621 37.453186, -89.494781 37.491726, -89.524971 37.571957, -89.513367 37.615928999999994, -89.51918 37.650375, -89.513374 37.67984, -89.521523 37.694798000000006, -89.581436 37.706103999999996, -89.666458 37.745453, -89.675858 37.78397, -89.691055 37.804794, -89.728447 37.840992, -89.851715 37.905063999999996, -89.861046 37.905486999999994, -89.866814 37.891875999999996, -89.900551 37.875904000000006, -89.937874 37.878044, -89.978912 37.911884, -89.958229 37.963634, -90.010811 37.969318, -90.041924 37.993206, -90.119339 38.032272000000006, -90.134712 38.05395100000001, -90.207527 38.08890500000001, -90.254059 38.122169000000014, -90.289635 38.16681700000001, -90.336716 38.18871300000001, -90.364769 38.23429899999999, -90.369347 38.32355899999999, -90.358688 38.36533, -90.339607 38.39084600000001, -90.301842 38.427357, -90.265785 38.518688, -90.26123 38.532768000000004, -90.240944 38.562805, -90.183708 38.61027100000001, -90.183578 38.658772, -90.20224 38.70036300000001, -90.196571 38.72396499999999, -90.163399 38.773098000000005, -90.135178 38.785484, -90.121727 38.80051, -90.113121 38.830467, -90.132812 38.85303099999999, -90.243927 38.91450900000001, -90.278931 38.92471699999999, -90.31974 38.92490799999999, -90.413071 38.96233000000001, -90.469841 38.959179000000006, -90.530426 38.89160899999999, -90.570328 38.87132600000001, -90.627213 38.880795000000006, -90.668877 38.93525299999999, -90.70607 39.037791999999996, -90.707588 39.058178, -90.690399 39.09370000000001, -90.716736 39.14421100000001, -90.718193 39.195873000000006, -90.732338 39.22474700000001, 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40.64381800000001, -91.162498 40.65631099999999, -91.129158 40.68214800000001, -91.119987 40.70540199999999, -91.092751 40.76154700000001, -91.088905 40.833729000000005, -91.04921 40.87958499999999, -90.983276 40.92392699999999, -90.960709 40.950503999999995, -90.954651 41.07036199999999, -90.957787 41.10435899999999, -90.990341 41.14437100000001, -91.018257 41.16582500000001, -91.05632 41.17625799999999, -91.101524 41.23152200000001, -91.102348 41.267818000000005, -91.07328 41.334895999999986, -91.055786 41.40137899999999, -91.027489 41.423508, -91.000694 41.431084, -90.949654 41.421234, -90.844139 41.44462200000001, -90.7799 41.449820999999986, -90.708214 41.450062, -90.658791 41.46231800000001, -90.6007 41.50958600000001, -90.54084 41.52597, -90.454994 41.527546, -90.434967 41.543578999999994, -90.423004 41.567272, -90.348366 41.586849, -90.339348 41.60279800000001, -90.341133 41.64909, -90.326027 41.722736, -90.304886 41.75646599999999, -90.25531 41.78173799999999, -90.195839 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38.90486100000001, -87.559059 38.869811999999996, -87.550507 38.857890999999995, -87.507889 38.795559, -87.519028 38.77669900000001, -87.508003 38.769722, -87.508316 38.73663300000001, -87.543892 38.68597399999999, -87.588478 38.672169, -87.625191 38.642810999999995, -87.628647 38.622917, -87.619827 38.599209, -87.640594 38.593177999999995, -87.652855 38.573871999999994, -87.672943 38.54742400000001, -87.65139 38.51536899999999, -87.653534 38.50044299999999, -87.679909 38.50400500000001, -87.692818 38.48153300000001, -87.756096 38.466125000000005, -87.758659 38.45709600000001, -87.738953 38.44548, -87.748428 38.41796500000001, -87.784019 38.378124000000014, -87.834503 38.35252399999999, -87.850082 38.28609800000001, -87.863007 38.28536199999999, -87.874039 38.316788, -87.883446 38.315552, -87.888466 38.300658999999996, -87.914108 38.281048, -87.913651 38.302345, -87.925919 38.30477099999999, -87.980019 38.241085, -87.986008 38.234814, -87.977928 38.200714000000005, -87.932289 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reprojected
MULTIPOLYGON (((-9804081.657847203 4510573.570048137, -9805898.28061746 4505702.664324028, -9830814.254324773 4501015.72870541, -9836098.59055273 4496313.788384076, -9842853.011976104 4497853.114945388, -9848173.081760604 4495115.335828296, -9853035.294479474 4480565.297336921, -9851933.788118074 4475099.443555139, -9846286.772989111 4467813.297693937, -9843149.455780085 4461000.643837322, -9846261.28082572 4452869.190793547, -9849192.211698815 4449167.506882168, -9850739.663940333 4448614.465657501, -9853697.756769184 4448138.739395508, -9858373.175382502 4449261.124945198, -9864489.847443119 4454317.452023299, -9872744.187685441 4457998.039407824, -9878392.872606762 4458804.050146454, -9879215.857602198 4460329.801924502, -9892216.081695508 4467327.6217995165, -9899920.948931275 4469593.788107706, -9906674.59111821 4469821.507927165, -9914674.121046105 4465045.034948174, -9920439.134835308 4454748.786355814, -9923725.954120472 4452103.546096644, -9926308.677626366 4448064.2434366895, 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Answer 2

The answer was very simple in the end. When I used this function I just took the first include my IDE was suggesing me to be correct. I was making use of org.geoserver.feature.ReprojectingFeatureCollection;

But somehow the code in this include is not working properly (at least not for me using GeoTools 20.0 - includes automatically loaded by maven). When using the Function as described in my question it was just changing the EPSG Code of the data but did not transform the data itself. That's why further manipulation achieved false outputs (buffering for example still took place in degrees instead of meter).

I did not imediately noticed because when I importet test data into QGis, QGis transformed the data on the fly to the CRS it said it would be. When I finally made a GeoJSON out of it to look at the geometry values itself I realised that something was not right.

Long talk short solution. I changed the import to org.geotools.data.store.ReprojectingFeatureCollection; and that fixed the problem. Now it works like it should.

Don't know if it was my stupidity or if there is a bug in this include for real though.