CAPITULO V DE LOS TESOROS
DE LA SERVIDUMBRE LEGAL DE ACUEDUCTO
The Overwatch Progress Windows shows the status after most operations. The information reported varies depending on the task initiated. The window looks similar to the following:
LIDAR Analyst 5.1.x Tutorial | 125 Advanced Lesson
Point Cloud File Classifier Dialog
The Point Cloud Classifier dialog is used to classify points once you have extracted your bare earth, buildings, and vegetation features.
Access Location:
LIDAR Analyst
Menu (LIDAR Analyst Toolbar): LIDAR Analyst > Extraction
Toolbar: LIDAR Analyst
Command: Classify Point Cloud
Doc Id: 10321
Figure 91: Point Cloud Classifier
Point Cloud File Classifier Options
Single/last return
Displays the selected single/last return image.
First return
Displays the selected first return image.
Bare earth
Allows you to choose the bare earth file.
Input LAS file Buildings
Display the selected buildings image.
Forests
Display the selected forests image.
Tree points
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Horizontal units
Sets the horizontal units including Unknown, Inches, Feet, Miles, Centimeters, Meters, Kilometers, Decimal Degrees, Minutes, Seconds, and Radians.
Vertical units
Sets the vertical units including Unknown, Inches, Feet, Miles, Centimeters, Meters, and Kilometers.
Ignore already classified points
Select this option to maintain classes already assigned to points. If cleared, the classifier will reclassify points that were previously categorized.
Ground height threshold
Points that fall within this value of the bare ground (in the bare earth extraction) will be classified as ground. Default is 0.2 meters.
Minimum height
Points with a height of at least this value above the bare ground that fall within a building polygon will be classified as a building (if not classified as ground). Points classified as ground or buildings will not be considered for vegetation. The default is 2.2 meters.
Search radius
Defines the buffer to apply around a building when classifying the LAS points. The default is 1 meter.
Low vegetation
Low-lying vegetation, such as shrubs, with a height of at least this value. Using 0.3 meter, points that are greater than or equal to 0.3 meter in height and less than 1 meter will be categorized as Low vegetation. The default is 0.3 meter.
Medium vegetation
Mid-sized vegetation, such as shrubs and immature trees, with a height of at least this value. Using 1 meter, points that are greater than or equal to 1 meter in height and less than 2 meters will be categorized as Medium vegetation. The default is 1 meter.
High vegetation
Tall vegetation, such as mature trees, with a height of at least this value. Using 2 meters, points that are greater than or equal to 2 meters in height will fall into the High vegetation class. The default is 2 meters.
Reset to defaults
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Point Cloud to Raster Dialog
The Point Cloud to Raster dialog is where interpolation, raster properties, and cell size are configured. You can also set column and row raster properties.
Access Location:
LIDAR Analyst
Toolbar: LIDAR Analyst
Command: Point Cloud to Raster with Filtering
Menu (LIDAR Analyst Toolbar): LIDAR Analyst > Point Cloud Tools
Doc Id: 9915
Figure 92: Point Cloud to Raster
Related Procedures:
Reference Guide:
Point Cloud Data Chapter - Selecting a Point Cloud File to Convert to Raster
Point Cloud to Raster Options
Input file
Displays the name of the selected file to be converted.
Interpolation field
Allows you to select Elevation to create a raster DEM for the input LAS file, or Intensity to create an intensity raster from the LAS file.
Elevation - Creates a raster DEM for the input LAS file.
Intensity - Creates an intensity raster from the LAS file. The Intensity (Int) field displays
under Extents Information in the LAS header. If a dataset does not contain intensity values, you cannot create an intensity raster.
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Fill holes in data
Selecting this option will fill any regions containing no LAS points with an interpolated surface. In most cases, you will not want these regions to be filled with a surface. Typically, holes occur in LAS files due to the non-existence of data (holes can occur due to water features, bad data, shadow regions, or removal of points). Since holes are defined by their occurrence within the convex hull of the entire dataset, (i.e., there are points surrounding the hole in all directions), they can only be filled in reliably if they are small. If the holes are large, you can get interpolation artifacts as a result of the distance of the points used to fill in the holes.
Set output raster properties from input LAS file Set output raster properties from template raster
Allows you go choose template from a list.
Manually specify cell size
When selected, allows you to manually specify the cell size as opposed to using the default cell size.
X cell size
Reflects the X cell size of the point spacing you enter.
Y cell size
Reflects the Y cell size of the point spacing you enter.
Note: The X and Y values are the same as the point spacing value for the LAS file data. The fields
are automatically updated with the value entered in the point spacing field on the LAS File Selector (on page 123) dialog.
Number of columns
Displays the number of columns for the output raster dataset.
Number of rows
LIDAR Analyst 5.1.x Tutorial | 129 Advanced Lesson
Process Bare Earth Modifications Dialog
The Process Bare Earth Modifications dialog is used to configure and process a bare earth modification layer after you have identified points to add or delete.
Access Location:
LIDAR Analyst
Toolbar: LIDAR Analyst
Menu (LIDAR Analyst Toolbar): LIDAR Analyst > Clean-up
Doc Id: 9995
Figure 93: Process Bare Earth Modifications
Related Procedures
Reference Guide:
Cleanup Bare Earth Results Chapter - Creating a Bare Earth Modification Layer
Process Bare Earth Modifications Options
Bare earth
Allows you to choose the bare earth file for the bare earth modification layer.
Single/last return
Displays the selected single/last return image.
First return
Displays the selected first return image.
Ground points
Displays the ground points layer.
Ground mask
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Ground mask edits
Displays the ground mask edits layer.
Horizontal units
Allows you to choose the horizontal units for the bare earth modification including Unknown, Inches, Feet, Miles, Centimeters, Meters, Kilometers, Decimal Degrees, Minutes, Seconds, and Radians.
Vertical units
Allows you to choose the vertical units for the bare earth modification including Unknown, Inches, Feet, Miles, Centimeters, Meters, and Kilometers.
Auto-detect no-data regions (pre-process)
Large, flat areas of 100 square meters or more that are filled with a single value or no value are considered "no-data" regions. Bodies of water, which produce inaccurate LIDAR values, are typical of such resulting features. Selecting this option enables a search for no-data regions in the DEMs and removes such regions from the list of regions that will be processed for bare earth. Since large, perfectly flat regions do not occur naturally, selecting this option will produce better results. The option is selected by default.
Remove spikes and pits before processing (pre-process)
Selecting this option enables a search for and the removal of spikes and pits caused by anomalies in the input DEMs. Use this option only if the LIDAR data was not cleaned by the vendor. It is better to run this process as a separate, post-processing option, where you will have more control over the removal parameters. By default, this option is not selected.
Remove negative nDSM regions (post-process)
Since the extracted bare earth layer is an estimate of the bare-ground with features removed, it can lead to a normalized Digital Surface Model (nDSM) with negative values. The negative nDSM value corresponds to an area where the extractor estimated the bare earth surface to be higher than the actual surface height. These regions can therefore be safely set to the actual DEM height. A flattened DEM model is obtained using the formula: nDSM = DEM – bare earth. Selecting this option results in all nDSM regions being replaced with last-return DEM values, thus setting those regions to an nDSM value of zero. If you find large height variations in your bare earth, you can try selecting this option and running your bare earth extraction again. By default, this option is not selected.
Smooth bare earth using low-pass filter (post-process) removes cars, shrubs, and low height objects
Selecting this option runs a Low-Pass Filter (LPF) on the extracted bare earth. Through a
smoothing effect, the LPF removes the appearance of cars, shrubs, and low objects from the bare earth. By default, this option is not selected.
Bare earth output
Displays the output location for the bare earth modification.
Reset to defaults
Resets all bare earth modification settings to the default settings.
More
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Output last return if elevation difference between last return and ground surface estimate is - If the distance between the last-return (or single return) DEM and the
extracted bare earth is lower than this threshold, than that region will be replaced with values from the last-return DEM. This step adds fidelity to the extracted bare earth. If this value is set to 0, then the output bare earth will be the original interpolated bare earth with post-processing clean-up applied. The default is 0.5 meters.
Cleanup bare earth (post-process) - Selecting this option applies a "noise" filter to the
bare earth. The noise filter removes small imperfections, resulting in a smoother looking bare earth. Used in conjunction with the More smooth/Less Smooth slider. Selected by default.
More smooth/Less smooth slider - If you select Cleanup bare earth, use the slider bar to
set the smoothing tolerance. The slider determines how much noise to remove. The further to the right (Less smooth) the slider is moved, the lower the effect of the filter, the fewer regions to which the filter is applied, and the fewer imperfections that will be removed.
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