OPTIONAL EXERCISE 5: IMPORTING LIDAR DATA INTO ARCGIS TO MODEL FOREST STRUCTURE

Transcription

1 Exercise Objec ves This exercise is designed to provide you with possible silvicultural uses for lidar technology. You will begin by expor ng your LIDAR canopy height, canopy closure, and vegeta on density models from Fusion so ware into ArcGIS. You will then use Spa al Analyst tools to model forests with average canopy heights and densi es that are typical of mul and single story old growth habitat. Prerequisites Successful comple on of Op onal Exercises 1 4. Overview of Major Steps 1. Export.dtm files using Fusion DTM export u lity. 2. Load Spa al Analyst Extension. 3. Import Fusion export files into ArcGIS (DTM files). 4. Create habitat models in ArcGIS. Op onal Exercise 5 page 1

2 1. Export Fusion DTM Files (canopy height, canopy closure & vegeta on density model) a. Start Fusion 1. Click Tools Terrain Model Export model Click the first (upper) browse bu on and navigate to cover15.dtm (input) 4. Click the second (lower) browse bu on and navigate to an output directory; call the output file cover15.asc. When typing your output file name, be sure to manually type in the file extension.asc. 5. Select ASCII grid file for the output format. 6. Click Export and click OK to close the no fica on dialog. b. Now export the vegeta on density model; you can leave the window open, just change the se ngs. 1. Click the first (upper) browse bu on and navigate to cover2_14.dtm (input) 2. Click the second (lower) browse bu on and navigate to an output directory, call the output file cover2_14.asc. 3. Select ASCII grid file for the output format 4. Click Export. Click OK to close the no fica on dialog. c. Now export the canopy height model. 1. Click the first (upper) browse bu on and navigate to lub_chm.dtm (input) 2. Click the second (lower) browse bu on and navigate to an output directory, call the output file lub_chm.asc. 3. Select ASCII grid file for the output format 4. Click Export. Click OK to close the no fica on dialog. 5. Click Close. NOTE: You actually don t need to load anything into FUSION to use the Export Model command. There is NO indica on of processing while the Export Model u lity is running. You will receive a message of successful comple on a er the process has finished. You have now exported the canopy height model, canopy closure model, and the vegeta on density model. Now let s import these ASCII grid files into ArcGIS. 2. Load the Spa al Analyst Extension Note: There is also a command line program called DTM2ASCII that does the.dtm to Arc ASCII raster conversion from the command line. This tool will select integer or float formats depending on the precision in the.dtm file. If you already have Spa al Analyst loaded you may skip this sec on and move on to the next sec on. a. Open a new empty ArcMap Document 1. Click Start All Programs ArcGIS ArcMap. Op onal Exercise 5 page 2

3 2. In the Ge ng Started window click New Maps in the le column and then under My Templates click Blank Map. 3. In the top toolbar click Customize Extensions; in the list of extensions, find Spa al Analyst and place a check mark next to the name by clicking the box. Click Close. 4. Right click anywhere on the ArcMap toolbar and find Spa al Analyst in the list of toolbars; place a check mark by the name. The Spa al Analyst toolbar should now be loaded to your ArcMap document. 3. Import Canopy Height Model, Canopy Closure Model, and Vegeta on Density Model into ArcGIS a. Since your exported DTMs are now in ASCII format, we will import our DTM surfaces using the Arc ASCII import u lity. 1. Click on the Search window icon. 2. In the keyword search box, type in ascii. 3. Click on ASCII to Raster (conversion) and the setup window will appear. 4. Set the Input ASCII raster file to cover15.asc 5. Change the Files of type to File (*.ASC) 6. Navigate to your output directory and call the output grid file cover15_grid 7. Set the output data type to Float. Click OK 8. Repeat steps 3 thru 7 for the vegeta on density model (cover2_14.asc) and the canopy height model (lub_chm.asc) and call the output raster's cover2_14grid and lub_chmgrid respec vely. The Search window b. Click the Add Data bu on (in the ArcMap main toolbar) and add the three.asc files you just created. You have successfully imported three ASCII Grids into ArcGIS. These grids represent the canopy closure model, vegeta on density model, and canopy height model from the original LIDAR dataset. The models you imported into ArcMap will be used in part 4 of this exercise. The FUSION generated Canopy Height Model displayed in ArcMap. Op onal Exercise 5 page 3

4 4. Create habitat models in ArcGIS To create old growth habitat models we need to define some parameters. For this exercise we will set a minimum tree height of 70 feet and a canopy closure of 50% or more. We will also differen ate between single and mul story models using the vegeta on density model. A rela ve vegeta on density >= 25% (within our height strata of 2 14 meters) will be considered a mul story old growth habitat and < 25% rela ve vegeta on density will be considered a single story old growth habitat. These figures are arbitrary and do not represent a realis c model, but demonstrate the poten al for using LIDAR data in modeling 3 D forest structure. a. Click on the Search window icon again. 1. In the keyword search box type raster calculator. 2. Click Raster Calculator (Spa al Analyst). See top right graphic. 3. We will now apply the condi onal (con) command to the canopy height model and set a threshold value of 70 feet (21.3 meters) to define areas of old growth. Make sure that you follow this syntax EXACTLY, the raster calculator can be picky if you miss a space or a parentheses ). To help you avoid syntax typos, you can double click names, symbols, and numbers from the listed datasets, and keys provided. Hint Use the = key from your keyboard, as the = from the calculator will produce an == which will produce an error. 4. Enter the following equa on into the Raster Calculator exactly as follows: The above command line translates to. output file = condi on (if lub_chmgrid values are > 21.3, assign those pixels a value of 1 )...where 1 is equal to or synonymous to TRUE (where the condi on evaluates to true). 5. Set the Output raster as c:\lidar\sampledata\height_70. The result (right graphic) is a grid represen ng trees (red cells with value of 1) that have a height value of 70 feet or greater. b. We will apply the con command again, this me to the canopy closure model and set a threshold of 50% crown closure. 1. Open Raster Calculator from the Search window again. 2. Enter the following equa on into the Raster Calculator: height_70=con( lub_chmgrid.asc >=21.3,1) cover_50=con( cover15_grid >=50, 1) Raster Calculator Height_70 The above command line translates to. output file = condi on (if cover15_grid values are >= 50, then assign those pixels a value of 1 )...where 1 is equal to or synonymous to TRUE (where the condi on evaluates to true). Op onal Exercise 5 page 4

5 The result (top right graphic) is a grid represen ng trees (green cells with value of 1) that have a canopy coverage of 50% or greater. c. Now we will use the Raster Calculator to create a grid that shows areas with both condi ons met (height >= 70 and canopy closure >= 50%). 1. Open Raster Calculator. 2. Enter the following equa on into the Raster Calculator: Oldgrth= cover_50 * height_70 The resul ng grid (middle right graphic) will only display cells that meet the old growth requirements of both tree height and canopy coverage. Blue cells (value of 1) represent old growth areas. d. We will now create our last two grids represen ng mul story and single story old growth habitat. We will accomplish this by applying condi onal equa ons to the vegeta on density grid and mul plying the results by the old growth grid (Oldgrth) already created. Our final two grids will represent old growth habitat with varying densi es of lower canopy structure. 1. First lets create our mul -story old growth model. 2. Open Raster Calculator 3. Enter the following equa on into the Raster Calculator: Oldgrth_mult=Con( cover2_14grid >=25, 1)* Oldgrth The resul ng grid (bo om right graphic) will only display cells that meet the requirements of height, canopy closure and under story density (>=70 feet tall, >=50% Canopy Coverage, and >= 25% under story density) that we designated for our mul story old growth model. e. Now we will create our single story old growth model. 1. Open Raster Calculator 2. Enter the following equa on into the Raster Calculator: Oldgrth_sing=Con( cover2_14grid <25,1)* Oldgrth The resul ng grid (next page, top right graphic) will only display cells that meet the requirements of height, canopy coverage and under story density (>=70 feet tall, >=50% Canopy Coverage, and < 25% under story density) that we designated for our single story old growth model. f. Now lets add our reference image generated in exercise 3, so we can overlay our old growth models. 1. Click the Add Data Bu on.. Cover_50 Oldgrth Oldgrth_mul Op onal Exercise 5 page 5

6 2. Navigate to lub_ref.bmp, and click the Add bu on. 3. Le Click and drag Oldgrth_mult and Oldgrth_sing above lub_ref.bmp in the ArcMap index. Your finished product is a map document depic ng single and mul story old growth habitat overlaid on your reference image! Your finished product should look similar to the image below. Oldgrth_sing End of Op onal Exercise 5 Op onal Exercise 5 page 6