remove noise points

Author: JanCaha

src/alg.hpp

@@ -381,6 +381,7 @@ struct FilterNoise: public Alg
     std::string outputFile;
     std::string outputFormat;  // las / laz / copc
     std::string algorithm = "statistical"; // "statistical" or "radius"
+    bool removeNoisePoints = false;
 
     // radius params
     double radiusMinK = 2;
@@ -394,6 +395,7 @@ struct FilterNoise: public Alg
     pdal::Arg* argOutput = nullptr;
     pdal::Arg* argOutputFormat = nullptr;
     pdal::Arg* argAlgorithm = nullptr;
+    pdal::Arg* argRemoveNoisePoints = nullptr;
     pdal::Arg* argRadiusMinK = nullptr;
     pdal::Arg* argRadiusRadius = nullptr;
     pdal::Arg* argStatisticalMeanK = nullptr;

src/filter_noise.cpp

@@ -37,7 +37,8 @@ void FilterNoise::addArgs()
     argOutputFormat = &programArgs.add("output-format", "Output format (las/laz/copc)", outputFormat);
 
     argAlgorithm = &programArgs.add("algorithm", "Noise filtering algorithm to use: statistical or radius.", algorithm, "statistical");
-    
+    argRemoveNoisePoints = &programArgs.add("remove-noise-points", "Remove noise points from the output.", removeNoisePoints, false);
+
     // radius args
     argRadiusMinK = &programArgs.add("radius-min-k", "Minimum number of neighbors in radius (radius algorithm only).", radiusMinK, 2.0);
     argRadiusRadius = &programArgs.add("radius-radius", "Radius (radius method only).", radiusRadius, 1.0);
@@ -96,7 +97,7 @@ bool FilterNoise::checkArgs()
 }
 
 
-static std::unique_ptr<PipelineManager> pipeline(ParallelJobInfo *tile, pdal::Options &noiseFilterOptions)
+static std::unique_ptr<PipelineManager> pipeline(ParallelJobInfo *tile, pdal::Options &noiseFilterOptions, bool removeNoisePoints)
 {
     std::unique_ptr<PipelineManager> manager( new PipelineManager );
 
@@ -130,6 +131,13 @@ static std::unique_ptr<PipelineManager> pipeline(ParallelJobInfo *tile, pdal::Op
     }
 
     last = &manager->makeFilter("filters.outlier", *last, noiseFilterOptions);
+
+    if (removeNoisePoints)
+    {
+        Options filter_opts;
+        filter_opts.add(pdal::Option("expression", "Classification != 7"));
+        last = &manager->makeFilter( "filters.expression", *last, filter_opts);
+    }
 
     makeWriter(manager.get(), tile->outputFilename, last);
 
@@ -180,7 +188,7 @@ void FilterNoise::preparePipelines(std::vector<std::unique_ptr<PipelineManager>>
 
             tileOutputFiles.push_back(tile.outputFilename);
 
-            pipelines.push_back(pipeline(&tile, noiseFilterOptions));
+            pipelines.push_back(pipeline(&tile, noiseFilterOptions, removeNoisePoints));
         }
     }
     else
@@ -189,7 +197,7 @@ void FilterNoise::preparePipelines(std::vector<std::unique_ptr<PipelineManager>>
         tile.inputFilenames.push_back(inputFile);
         tile.outputFilename = outputFile;
 
-        pipelines.push_back(pipeline(&tile, noiseFilterOptions));
+        pipelines.push_back(pipeline(&tile, noiseFilterOptions, removeNoisePoints));
     }
 }
 

tests/test_filter_noise.py

@@ -136,3 +136,49 @@ def test_filter_noise_with_bad_algorithms():
 
     assert res.returncode == 0
     assert f"unknown algorithm: {unknown_algorithm}" in res.stderr
+
+
+def test_filter_noise_statistical_remove_noise_points():
+    """Test filter noise function with statistical on laz and removal of noise points"""
+
+    input_path = utils.test_data_filepath("stadium-utm.laz")
+    output_path = utils.test_data_output_filepath("filter_noise_remove_points.laz", "filter_noise")
+
+    res = subprocess.run(
+        [
+            utils.pdal_wrench_path(),
+            "filter_noise",
+            f"--input={input_path.as_posix()}",
+            f"--output={output_path.as_posix()}",
+            "--algorithm=statistical",
+            "--remove-noise-points=true",
+        ],
+        check=True,
+    )
+
+    assert res.returncode == 0
+
+    assert output_path.exists()
+
+    pipeline = pdal.Reader(filename=output_path.as_posix()).pipeline()
+
+    pipeline.execute()
+
+    values = pipeline.arrays[0]["Classification"]
+    unique_values = np.unique(values)
+
+    assert unique_values.size == 2
+    assert unique_values.tolist() == [1, 2]  # 1: non-ground, 2: ground
+
+    nonground_point = pipeline.arrays[0][
+        (pipeline.arrays[0]["X"] == 494629.19000000006) & (pipeline.arrays[0]["Y"] == 4878441.75)
+    ]
+    assert nonground_point["Classification"] == 1  # non-ground
+    assert nonground_point["Z"] == 129.14
+
+    ground_point = pipeline.arrays[0][(pipeline.arrays[0]["X"] == 494657.37) & (pipeline.arrays[0]["Y"] == 4878358.05)]
+    assert ground_point["Classification"] == 2  # ground
+    assert ground_point["Z"] == 130.15999999999997
+
+    noise_point = pipeline.arrays[0][(pipeline.arrays[0]["X"] == 494650.53) & (pipeline.arrays[0]["Y"] == 4878439.98)]
+    assert noise_point.size == 0