TRAINING MODULE FOR POINT CLOUD DATA GENERATION USING ERDAS IMAGINE AND CONVERSION OF LAS DATA TO DSM RASTER USING ARCGIS SOFTWARE Siddhartha Kharea∗,Hooman Latifib, Sanjay Kumar Ghosha a
Geomatics Engineering Group, Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India- (sidk4dce, scangfce)@iitr.ac.in b
Dept. of Remote Sensing, University of Würzburg, Oswald-Külpe-Weg 86, 97074 Würzburg, Germany -
[email protected]
European Space Agency Project Project Id: 33429
Title
Object Based approaches for remote sensing-assisted assessment of forest biodiversity focusing on plant species diversity and forest structural parameters
Type
Restrained Dataset
Class
Peer Review
Primary Application Domain
Land Environment
POINT CLOUD DATA GENERATION USING ERDAS IMAGINE
MODULE I 1. Click on Toolbox and Select Imagine Photogrammetry option.
2. Imagine Photogrammetry Project Manager window will pop up. Presently all the operation options are disabled now because we have not set any parameters.
3. Click on File option of Main menu and select New option.
4. A create New Block File dialog box will appear. Give any suitable file name and click ok.
5. Once you create new block file (test.blk in this example) then a Model Setup dialog box will appear. Select Rational functions under Geometric Model Category and then select SPOT 6 RPC option under Geometric Model options. Then Click ok.
6. Now a Block Property Setup dialog box will appear. In front of Projection option click on Set option.
7. It will ask to select the Projection system. In this example UTM WGS 84 North option was selected. Then click ok on Projection Chooser dialog box.
8. Now UTM option is visible in front of Projection option and WGS 84 is appearing in front of Datum option. Now click ok on Block Property Setup dialog box.
9. After setting Sensor Model parameters and Projection system, all the operation options within Imagine Photogrammetry Project Manager Window for Test.blk block file is now enabled.
10. Now click on Edit option of Main menu and click on Add Frame option which will open an Image File Name dialog box and now select the left image from the SPOT or other sensor stereo pair and then click Ok.
Again perform the step 10 for right image of Stereo pair datasets.
11. Once you select the both (left and right) images of stereo pair then both the images will get loaded in test.blk Project manager. Make sure that Pyr (i.e. Pyramid Layer) and Online option should be green now. This shows that you have successfully loaded the stereo pairs. Other options are still showing red colour.
12. Now we have to provide the interior and exterior orientation parameters to carry out further analysis. Therefore click on Int. option. Once you click on Int. option a dialog box will appear and it will ask you select the RPC coefficient file of the respective sensor (in this case SPOT 6 RPC file).
13. In front of file type select the required file format (in this case RPC file is in .XML format) and select the RPC coefficient file provided by the data distributor. Then click ok on File Chooser dialog box.
14. Now it will go back to the RPC frame editor window. Now click on next option and select the RPC coefficient file for right image of stereo pair in similar way as explained in Step 13. And then click ok.
15. Once the RPC Coefficients files were loaded for left and right images then Int. and Ext. options colour changes to green from red colour. Further, Project Manager window starts showing the Stereo pairs with overlap regions.
16. Now click again on Edit option of main menu and click on Auto. Tie Point Generation Properties option.
17. Now Automatic Tie Point Generation Properties dialog box will appear. In this property box select the General tab and choose Active Images Only option and Exterior/Header/GCP option. Now select Distribution tab and select Default distribution option and provide number of points under Input Intended Number of Points option (here 150 is given) and then click Run option.
18. Once tie point generation was done an Auto Tie Summary dialog box will appear. It will display the summary in terms of accuracy of tie point generations. If you are satisfied with the success rate then close the dialog box otherwise repeat step 17 with different number of input tie point options.
19. Now all the tie point locations appear on Stereo pair dataset within Project Manager Window. Now click on Start Point Measurement Tool option.
20. It will ask you to select the type of point measurement tool. Select the Classic Point Measurement Tool and Click ok.
21. Now Point Measurement window will open and displays left and right images along with the tie points. Cross check the locations of tie points matching and then click on Perform triangulation option.
22. Once triangulation was performed then a Refinement Summary dialog box will appear. This box shows the RMSE value. If it in acceptable range then click on Accept option and close this dialog box. 23. Now go back to Point Measurement window and click on Save option and save all the results of triangulation. Now close Point Measurement widow.
23. Now go back to Project Manager window and click on the red colour under Ortho option.
24. Now Ortho Resampling dialog box will appear. This operation will create orthorectified image output of input left image and right image respectively. Provide the location of Output file and change the other parameters as per your requirement and then click ok.
25. Once orthorectified images were generated then red colour under ortho option turned into green.
26. In order to extract the DTM or to generate the point cloud data for high spatial resolution stereo pairs, click on Process option of main menu and Select eATE option under DTM Extraction option.
27. Now click on Yes option for both the Attention dialog box and proceed with eATE analysis.
MODULE II This First section of this module covers the eATE workflow of ERDAS IMAGINE software to generate the point cloud data from orthorectified SPOT 6/7 stereo pair imageries. The Second section of this module covers the workflow of generation of DSM from point cloud data in Arc GIS software.
First Section 1. Inside eATE Manager Window select edit option of main menu and click on Strategy Manager Option.
2. Now Strategy Manager dialog box will appear. Select the path and input the name of Library file in your working folder. Change the Strategy name (in this example the name is testing) from default option. Inside Correlator option chose either NCC or SSD option (in this example NCC was selected). Change the window size as per the requirement, i.e. 3 by 3 or 5 by 5 or 7 by 7 etc. In this case 3 by 3 window size was given as an input. Similarly other options can be selected based upon the dataset. In this case we have selected the parameters by keeping consideration of input imageries. Therefore, figure shown below depicts the selected parameters for SPOT 6 /7 stereo pair. Now click on Save to Library option and then Save to Project option and then click on close button.
3. Again select edit option of main menu and click on Output Settings option.
4. Output Settings dialog box will appear. Now Select the General Tab and provide the Project File Directory Path to your working folder. Change the Min Z and Max Z values (in this case it was varying from 200 m to 2000 m).
5. Now click on Output files tab and check the Output Original Points option. This option will ask to provide the name of .las (point cloud data) file. Select the directory folder option and provide the path and name to the working folder (in this case the name is test_orgiginal_terrain.las). Maximum value of Million Points Per File can be 2000 only. User can reduce the value as per the requirement. Do not change other options and then click OK button.
6. Now again inside edit option select Process Engine Settings option.
7. Inside Process Engine Settings dialog box select the Default Strategy Name which you have created earlier (in this case testing) and keep other options as default and click Ok. If user wants to change the values of other parameters then refer to help file for the explanation of each parameter.
8. Now select Process option of main menu and click on Batch Run eATE.
9. This will open Output Setting dialog box again. Inside Output Settings dialog box click on General Tab and cross check the Project File Directory path. The other options of tabs are for LiDAR data processing therefore users are advised to not make any changes while using optical Stereo Pair datasets. Now click on Batch Run button and wait for the competition of processing.
10. Once the processing is done, users can visualise the generated point cloud data in ERDAS IMAGINE software. Right click on 2D view inside contents and click on Open Point Cloud layer option and select the respective point cloud data file (with .las extension).
11. Figure Shown below depicts the final outcome of point cloud generated from high spatial resolution optical Stereo pair of SPOT 6 dataset. Once point cloud data was loaded in 2D view, Point Cloud option will appear on the main menu.
12. Click on Point Cloud option of main menu and then play around with different available options and it is advised to create subsets of .las data. Handling subsets are easier and it will reduce the computation time also.
Second Section 1. Since ArcGIS support .lasd extension therefore, we will first convert .las file to .lasd format then further processing will be carried out. Open ArcMap and make sure LAS dataset extension is enabled. Now click on ArcToolbox option and then expand Data Management Tools option and the inside LAS Dataset option clicks on Create LAS dataset operation.
2. Now Create LAS Dataset dialog box will appear. Browse for the .las file (point cloud data file) created before (in this case may_2014_l1_new.las). Now provide the name of Output LAS dataset file to your working directory (in this case test_lasdata.lasd) and then Click Ok.
3. Figure shown below depicts the LAS dataset generated from point cloud data.
4. Now choose Elevation mode as a display mode inside LAS Dataset extension.
5. Elevation Mode displays the LAS dataset in Map view and it also categorised the elevation ranges according the assigned colours.
6. In order to convert LAS dataset (.lasd file) to DSM (i.e. raster dataset with .tif extension) expand the Conversion Tool inside ArcToolbox and then click on To Raster option. Now click on LAS Dataset to Raster option. This will open LAS Dataset to Raster dialog box. Now browse for Input LAS Dataset and provide the name of output Raster file to be created. User can select the Interpolation Type method (either Binning or Triangulation) based upon the requirement. Further, user can also change the Data type and Sampling value (spatial resolution) of output raster dataset. Once all the parameters were selected then click Ok.
7. Once the processing is done then load the generated Raster dataset in the Layers option of ArcMap. Figure below displays the final generated DSM raster dataset in the Map view.
