LiDAR Point Cloud Manager: Difference between revisions

Latest revision as of 12:24, 1 April 2020

The LiDAR Point Cloud Manager analyzes the vegetation within the forest and creates a vegetation raster map. The analys is based on a ocdLas file created when importing las files in the DEM Import Wizard.

Load

This function loads an OCAD LAS file (*.ocdLas) and opens the LiDAR Point Cloud Manager. Alternatively, just drag and drop an ocdLas file into the drawing area.

The OCAD LAS file is a LiDAR point cloud in an OCAD internal file format created in the DEM Import Wizard. This file is optimized for fast access to the LiDAR points.

For more information about this file open the Information dialog.

Info

This function shows information about the ocdLas file.

When moving the mouse cursor over the file name then the full file path appears.

Show Frame

This function shows a red rectangle with the extent of the loaded ocdLas file.

Close

This function closes ocdLas file.

Manage

This function reopens the LiDAR Point Cloud Manager with the already loaded ocdLas file.

Filtering

This function shows the LiDAR point cloud as image according to the settings in filtering options.

It is the same extent as on the drawing area in the OCAD File. The pixel size depends on the zoom level in the drawing area. When moving the cursor over the point cloud image the coordinate of the mouse cursor is shown in the status bar.

In the Filtering tab there are four different display options: Classification, Intensity, Height over ground and Vegetation density.

Display Option Classification

This option shows the classification of the LiDAR points. If more than one point is inside one cell then the point with the higher priority is shown. For example, the class Building has higher priority than Vegetation and Ground has the lowest priority.

Ground = Brown, Low Vegetation = Dark Green, Medium Vegetation = Light Green, High Vegetation = Green, Buliding = Black, Low Point = Grey

Display Option Intensity

This option shows the intensity of the LiDAR points. Lower intensity is drawn with darker color. In this image the different types of vegetation (deciduous and coniferous forest) and the vegetation boundaries are visible.

Display Option Height Over Ground

This option shows the maximum height above ground for each cell. In this image, high trees and vegetation boundaries can be detected. The structure of the forest can be seen clearly.

Display Option Vegetation Density

This option shows the number of LiDAR points for each cell. Cells with more points are shown in darker red. Open areas have often less return points and appear therefore in lighter red.

Click the Save image button to create a geo-referenced png file from the current point cloud image and load it as new background map. The file is automatically saved in the same folder as the ocd file.

Classification

A list with the different classifications is shown. The value in parentheses is the number of points for this class. In some cases it is recommended to uncheck the Overlap points. The overlapping points come from the different flight lines.

Click the Low vegetation button to choose only the Low vegetation points and set the Height above ground filter to 0.1 - 1.0 m.

Click the Medium vegetation button to choose only the Medium vegetation points and set the Height above ground filter to 1.0 - 3.0 m.

Return Type

Choose which return types are shown. By default 'All returns' is chosen.

Height Above Ground

This function filters the points with the height above ground. To show only near-ground vegetation points move the left slider to 0.0 and the right to 3.0.

Vegetation Base Map

This function creates an Orienteering base map with user-defined information about the near-ground vegetation. Near-ground means between ground and 3m above. When using this function the first time default values are set. The default values are optimized for Steinhauserwald in Switzerland and LiDAR data from Canton Zürich. The settings depend on the forest type and the LiDAR data.

Cell size

Choose the cell size.

Undergroth and Vegetation

Range From

Choose the range in which points should be considered as Undergrowth and Vegetation.

Neighborhood kernel

Choose the amount of neighbouring cells for the calculation.

Thresholds

The calculation based on the NDVD (Normalized Difference Vegetation Density). The thresholds for the undergrowth and the vegetation shall be between -1.0 and +1.0. The thresholds can be calculated with samples in the Statistics function. The meaning of the thresholds is visible in the image below.

Overlap Points from

Overlap points is a classification type of LAS file format. These unclassified overlap points come from different scans (flight lines). Choose the lower threshold in which points should be considered as Undergrowth and Vegetation. If this as value is too low, ground points are used as undergrowth and vegetation points.

Use filter

Use filter to generalize the map.

Show area with no data in red color

Area with no data are shown in red color if the value is set to True. Otherwise the cells are white and not specifiable from the forest cells. The filter option generalizes the raster map.

Click the Create button to calculate and show the Orienteering base map. The map is drawn with the following colors:

Click the Save image button to create a geo-referenced png file and load it as new background map. The file is automatically saved in the same folder as the ocd file.

The example below shows the Orienteering base map (left) and the map from field work (right).

Statistics

The statistics function can calculate the vegetation thresholds from samples.

OCAD uses Microsoft Excel for this function. If Excel is not installed the following error message appears.

The following steps are to do:

Import Symbol from Template File
Draw Samples
Create Statistics

Import Symbol from Template File

Press the Shift key and click File -> Import. The file chooser opens in the Template subfolder of the OCAD program folder. Choose the Template Vegetation Samples.ocd file and click Open. In the Import OCAD Map dialog choose the option to Import all symbols and colors and at the top of the color table.

Click OK. The 6 imported symbols are in the symbol box.

The symbol are for the vegetation samples and have the following meaning:

Draw Samples

Use these 6 symbols and draw samples for the expected vegetation. We recommend to draw totally more than 100 samples for the desired area.

Create Statistics

Click the Create statistics button to create an Excel file. The file opens automatically if Excel is installed.

The 5 thresholds (marked in yellow color in the images bellow) can be inserted in the Raster map settings.

Profile

The profile shows the vegetation structure.

In the OCAD window, choose any line symbol and draw a straight line inside the loaded ocdLas file and select the line object afterwards.

In the LiDAR Point Cloud Manager window, choose the profile width and click the Show button. OCAD draws the profile according to the filter settings in the Filtering tab.

@@ Line 1: / Line 1: @@
-The LiDAR Point Cloud Manager analyzes the vegetation within the forest and creates a vegetation raster map. The analysis based on a [[DEM_Import_Wizard#Create_ocdLas|ocdLas]] file created when importing las files in the '''[[DEM_Import_Wizard|DEM Import Wizard]]'''.
+The LiDAR Point Cloud Manager analyzes the vegetation within the forest and creates a vegetation raster map. The analys is based on a [[DEM_Import_Wizard#Create_ocdLas|ocdLas]] file created when importing las files in the '''[[DEM_Import_Wizard|DEM Import Wizard]]'''.
 ==Load==
 This function loads an OCAD LAS file (*.ocdLas) and opens the '''[[LiDAR_Point_Cloud_Manager#Manage|LiDAR Point Cloud Manager]]'''.
+Alternatively, just drag and drop an ocdLas file into the drawing area.
 The OCAD LAS file is a LiDAR point cloud in an OCAD internal file format created in the [[DEM_Import_Wizard#Create_ocdLas|DEM Import Wizard]]. This file is optimized for fast access to the LiDAR points.
@@ Line 25: / Line 26: @@
 This function reopens the '''LiDAR Point Cloud Manager''' with the already [[LiDAR Point Cloud Manager#Load|loaded ocdLas file]].
-==Point Cloud==
+==Filtering==
-This functions shows the LiDAR point cloud as image according to the settings in filtering options.
+This function shows the LiDAR point cloud as image according to the settings in filtering options.
 [[File:LidarPointCloudManager PointCloud.png]]
-It is the same extent as on the drawing area. The pixel size depends on the zoom level in the drawing area. When moving the cursor over the point cloud image the coordinate of the mouse cursor is shown in the status bar.
+It is the same extent as on the drawing area in the OCAD File. The pixel size depends on the zoom level in the drawing area. When moving the cursor over the point cloud image the coordinate of the mouse cursor is shown in the status bar.
 In the ''Filtering'' tab there are four different display options: Classification, Intensity, Height over ground and Vegetation density.
 ==== Display Option Classification ====
 This option shows the classification of the LiDAR points. If more than one point is inside one cell then the point with the higher priority is shown. For example, the class ''Building'' has higher priority than ''Vegetation'' and ''Ground'' has the lowest priority.
 [[File:LidarPointCloudManager_Classification.png]]
+''Ground = Brown, Low Vegetation = Dark Green, Medium Vegetation = Light Green, High Vegetation = Green, Buliding = Black, Low Point = Grey''
 ====Display Option Intensity ====
@@ Line 44: / Line 48: @@
 ==== Display Option Height Over Ground====
-This option shows the maximum height above ground for each cell. In this image high trees and vegetation boundaries can be detected.
+This option shows the maximum height above ground for each cell. In this image, high trees and vegetation boundaries can be detected. The structure of the forest can be seen clearly.
 [[File:LidarPointCloudManager_HeightOverGround.png]]
 ==== Display Option Vegetation Density====
-This option shows the number of LiDAR points for each cell. Cells with more points are shown in darker red. Open areas have often less return points and appears therefore in lighter red.
+This option shows the number of LiDAR points for each cell. Cells with more points are shown in darker red. Open areas have often less return points and appear therefore in lighter red.
 [[File:LidarPointCloudManager_VegetationDensity.png]]
-Click the '''Save''' button to create a geo-referenced png file from the point cloud image and load it as new background map. The file is automatically saved in the same folder as the ocd file.
+Click the '''Save image''' button to create a geo-referenced png file from the current point cloud image and load it as new background map. The file is automatically saved in the same folder as the ocd file.
 ===Classification===
@@ Line 78: / Line 82: @@
 [[File:LidarPointCloudManager PointCloud Classification HeightAboveGround.png]]
-==Profile==
+==Vegetation Base Map==
-The profile shows the vegetation structure.
-Draw a straight line in the drawing area inside the loaded ocdLas file and select the line object.
-Choose the profile width and click the '''Show''' button. OCAD draws the profile according the filter settings in the '''Filtering''' tab.
-[[File:LidarPointCloudManager Profile.png|794px]]
-==Raster Map==
 This function creates an ''Orienteering base map'' with user-defined information about the near-ground vegetation. Near-ground means between ground and 3m above.
 When using this function the first time default values are set. The default values are optimized for [https://map.geo.admin.ch/?lang=en&topic=ech&bgLayer=ch.swisstopo.pixelkarte-farbe&layers=ch.swisstopo.zeitreihen,ch.bfs.gebaeude_wohnungs_register,ch.bav.haltestellen-oev,ch.swisstopo.swisstlm3d-wanderwege&layers_visibility=false,false,false,false&layers_timestamp=18641231,,,&X=229174&Y=680276&zoom=10&crosshair=marker Steinhauserwald] in Switzerland and LiDAR data from Canton Zürich. The settings depend on the forest type and the LiDAR data.
@@ Line 93: / Line 88: @@
 [[File:LidarPointCloudManager RasterMap.png]]
-The cell size is 1m and the kernel size 5x5 (5m x 5m).
+=== Cell size===
+Choose the cell size.
+===Undergroth and Vegetation===
+====Range From====
+Choose the range in which points should be considered as Undergrowth and Vegetation.
+====Neighborhood kernel====
+Choose the amount of neighbouring cells for the calculation.
+====Thresholds====
 The calculation based on the NDVD (Normalized Difference Vegetation Density).
 The thresholds for the undergrowth and the vegetation shall be between -1.0 and +1.0. The thresholds can be calculated with samples in the '''[[LiDAR_Point_Cloud_Manager#Statistics|Statistics]]''' function. The meaning of the thresholds is visible in the image below.
@@ Line 100: / Line 104: @@
 [[File:LidarPointCloudManager Thresholds.png]]
-The thresholds for the undergrowth is from 0.0m to 1.0m and for the vegetation from 0.0m to 3.0m
+===Overlap Points from===
+Overlap points is a classification type of LAS file format. These unclassified overlap points come from different scans (flight lines).
+Choose the lower threshold in which points should be considered as Undergrowth and Vegetation. If this as value is too low, ground points are used as undergrowth and vegetation points.
+===Use filter===
+Use filter to generalize the map.
+===Show area with no data in red color===
 Area with no data are shown in red color if the value is set to ''True''. Otherwise the cells are white and not specifiable from the forest cells. The filter option generalizes the raster map.
-Click the '''Draw''' button to calculate and show the ''Orienteering base map''. The map is drawn with the following colors:
+Click the '''Create''' button to calculate and show the ''Orienteering base map''. The map is drawn with the following colors:
 [[File:LidarPointCloudManager OrienteeringBaseMapColors.png]]
@@ Line 118: / Line 129: @@
 [[File:LidarPointCloudManager Statistics.png]]
+OCAD uses Microsoft Excel for this function. If Excel is not installed the following error message appears.
+[[File:LidarPointCloudManagerStatisticsExcelErrorMessage.png]]
 The following steps are to do:
@@ Line 125: / Line 140: @@
 === Import Symbol from Template File===
-Press the '''Shift''' key and click '''File''' -> '''Import'''. The file chooser opens in the ''Template'' subfolder of the OCAD program folder. Choose the ''Template Vegetation Samples.ocd'' file and click '''Open'''. In the Import OCAD Map dialog choose the option to ''Import all symbols and colors'' and ''at the top of the color table''.
+Press the '''Shift''' key and click '''File''' -> '''Import'''. The file chooser opens in the ''Template'' subfolder of the OCAD program folder. Choose the ''Template Vegetation Samples.ocd'' file and click '''Open'''. In the ''Import OCAD Map'' dialog choose the option to ''Import all symbols and colors'' and ''at the top of the color table''.
 [[File:LidarPointCloudManager PointCloud ImportOptions.png]]
-Click OK. The 6 imported symbol are in the symbol box.
+Click OK. The 6 imported symbols are in the symbol box.
 [[File:LidarPointCloudManager PointCloud SymbolBox.png]]
@@ Line 136: / Line 151: @@
 [[File:LidarPointCloudManager PointCloud Symbols.png|50%]]
 === Draw Samples===
 Use these 6 symbols and draw samples for the expected vegetation. We recommend to draw totally more than 100 samples for the desired area.
@@ Line 147: / Line 163: @@
 [[File:LidarPointCloudManager ThresholdsExcel.png]]
+==Profile==
+The profile shows the vegetation structure.
+In the OCAD window, choose any line symbol and draw a straight line inside the loaded ocdLas file and select the line object afterwards.
+In the LiDAR Point Cloud Manager window, choose the profile width and click the '''Show''' button. OCAD draws the profile according to the filter settings in the '''Filtering''' tab.
+[[File:LidarPointCloudManager Profile.png|794px]]