Difference between revisions of "Using Airborne Laserscanning Data for Orienteering Base Map Generation"

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=== Slope Gradient Map and Cliff Features ===
 
=== Slope Gradient Map and Cliff Features ===
 
:The Slope gradient Map also shows paths or relief features like the Hill shading Map.
 
:The Slope gradient Map also shows paths or relief features like the Hill shading Map.
:ToDo
+
[[File:DEMSlopeGradientExample.png]]<br>
 +
''The Slope gradient Map shows in this example basically the same as the Hill Shading Map.''
  
 
=== Classify Vegetation Height===
 
=== Classify Vegetation Height===

Revision as of 12:05, 26 July 2018

This tutorial shows a possible way to proceed LiDAR data in OCAD and how to use them when drawing orienteering maps.
In case you have access to LiDAR Data, we can highly recommend you working with it. As you will find out, working with LiDAR Data makes mapping easier, more accurate and faster.
You find more detailed information about the DEM Wizward here.

Open New File

Open OCAD.
Go to File -> New -> Orienteering map: Choose a symbol set for orienteering maps and choose the scale (e.g Orienteering Map ISOM 2017 10000.ocd).
Save the newly created file under File -> Save.

DEM Wizard

Open the DEM Wizard

Open the DEM Import Wizard in the DEM Menu.

DEMImportWizrad.png

Choose DEM Import File

Choose one or several importable files. In this tutorial we proceed a LAS-file.
Find more Information about this step here.

DEMImportFiles.png

DEM Settings

Here you can choose your favourite folder (in the upper right corner under File name) where all files should be stored .
In this tutorial, we have a look at all possible outputs. However, not all of them make sense for mapping as we discuss later in the section How to use the output. Enter the DEM Settings as follows.
Find more Information about this step here.

DEMSettings.png

LAS Settings

Select the LAS Settings as follows.
We will need the .ocdlas-File later in the LiDAR Point Cloud Manager section.
Find more information about this step here.

DEMLasSettings.png

DEMResultLasIntensity.png
DSM Intensity Map

DEMResultLasClassification.png
DSM Classification Map

Create Contour Lines

Select the settings to Create Contour Lines as follows.

Activate both boxes Create custom contours (no smoothing) and Create smoothed contours using TPI.
Choose as contour intervall 1m/5m/25m.
Click on Load symbols from template to get 12 line symbols at the bottom of your symbol box. The boxes will be filled automatically.
Choose Use different symbols for depression to distinguish depressions from hills.
Find more information about this step here.

DEMContourLines.png

DEMResulatContourLines.png
Contour Lines

Create Hypsometric Map

Select the settings to create a Create Hypsometric Map as follows.
Find more information about this step here.

DEMHypsometricMap.png

DEMResultHypsometric.png
Hypsometric Map

Create Hill Shading

Select the settings for Create Hill Shading as follows.
Find more information about this step here.

DEMHillShading.png

DEMResultHillShading.png
Hill Shading

Create Slope Gradient

Select the settings for Calculate Slope Gradient as follows.
Check Extract cliff features from black pixels.
Find more information about this step here.

DEMSlopeGradient.png

DEMResultSlopeGradient.png
Slope Gradient

DEMResulatExtractCliffs.png
Cliff features as vector symbol (Slope Gradient Map is dimmed).

Classify Vegetation Height

Select the settings for Classify Vegetation Height as follows.
Find more information about this step here.

DEMVegetationHeight.png

DEMResultVegetationHeightMap.png
Vegetation Height Map

Extract Features

Select the settings to Extract Features as follows.
Find more information about this step here.

DEMExtractFeatures.png

DEMResulatExtractFeatures.png
Extracted Features

Summary

This dialog shows the progress of the different functions.
During the calculation, a message concerning georeferncing the map will pop up (unless the map is already georefernced). Do not change anything and click on Ok. After finishing the process the dialog closes automatically.

DEMSummary.png

What is the output?

After finishing the DEM Wizard the dialog closes automatically and the results are shown.
All raster maps are loaded as background maps.
Contour lines, cliff features and extracted features are assigned to the corresponing symbols in the Symbol box.
All files are stored in the folder you can specify in the DEM Settings.

DEMDone.png
View after the DEM Wizard is done. Note the newly added Symbols at the end of the Symbol box on the right side.


DEMBackgroundMaps.png
All background maps have been loaded automatically.


DEMFiles.png
All generated files for this example. They are stored in the folder you specified in the DEM Settings.

How to use the output?

As you probably noticed, not all output files and derived data are usefull. We can give you the following recommendations:

Intensity Map and Classification Map

The Intensity map can be useful for mapping. You can see quite well Vegetation boundaries, forest tracks, single trees and open parts in the forest.

DEMIntensityExample.png
Example of an Intensity map. Compared to the Vegetation Height Map, you can see well vegetation boundaries (black forest= coniferous forest; grey forest = deciduous forest.

The Classification map is of no use for mapping.

Contour Lines

  • For mapping in the terrain, use the custom contour lines as background, where you have all details on it (provided you choose the contour interval small enough. 1m is an appropriate interval.)
  • To draw contour lines on the PC, first calculate and load the TPI contours and adapt them afterwards where needed. Use the Reshape function for adapting. Keep in mind, that these contours are smoothed and therefore not include all details. Some valleys or ridges appear flatter than they actually are. Nevertheless, especially in steep and constant slopes, the biggest part of the TPI contours can be adopted to your map without redrawing. You save a lot of time with it.
  • The destinction in hills and depression is recommended, as you get a faster and better understanding of the terrain.

DEMResultContour1.png
Smoothed contour lines in green, custom contor lines in blue. Orange and red ones for depressions.

Hypsometic Map

This map may be used for visualisation, but is obsolete for field work and mapping puropse.

Hill shading Map

The hill shading map can be useful to detect point and line objects like pits, paths or watercourses.

DEMHillShadingExample.png
Hill Shading Map of Bürenflue. Small pits and knoll as well as tracks and pathes are much better visible here than with contour lines.

Slope Gradient Map and Cliff Features

The Slope gradient Map also shows paths or relief features like the Hill shading Map.

DEMSlopeGradientExample.png
The Slope gradient Map shows in this example basically the same as the Hill Shading Map.

Classify Vegetation Height

ToDO

Extract features =

DEMResultContour2.png

DEMResultTrees.png


DEMReadyForMapping.PNG

LiDAR Point Cloud Manager

LPM.png
LPMLoad.png
LPMFilteringClassification.png
LPMFilteringHeightOverGround.png
LPMFilteringIntensity.png
LPMFilteringVegetationDensity.png

LPMMapSample.png
LPMRasterMap.png
LPMProfile2.png