How to make an Elevation Map. A Tool for using ArcGIS Project Group N11

Transcription

1 How to make an Elevation Map A Tool for using ArcGIS 10.1 Project Group N11

2 How to make an Elevation Map A Tool for using ArcGIS 10.1 Hogeschool Rotterdam Academieplein, Waterbouw R.M. Crooij, J. Banis, E. Prinsen, J. Booy, WAMDLT01P Mevr. M. Rutten Mevr. A. Mendez Dhr. K. van der Sand Dhr. E. Schaap Dhr. J. Lekkerkerk Dhr. W. de Ruijter Dhr. W. Kuppen Versie 2.0 Rotterdam, 28 januari 2017

3 Making an elevation map by using ArcGIS This document shows a step explanation of how to use the program ArcGIS 10.1 to make an elevation map of a location. This elevation map is part of the final document, the recommendation of an evacuation plan. The following mean steps are necessary to get to the end result: 1. Create an account to take data from Nyaungdon. 2. Use this data in ArcGIS to create an elevation map. Create an account and collect data from Nyaungdon 1. To gather the data of Nyaungdon an account on the following website is needed: Fill in all the boxes and agree the terms of use. After you agreed the terms of use you press Input Check Figure 1: Fill in the boxes and check 'agree'.

4 2. Go to your account, select the following link: and fill in your ID ( ) and Password. Now we have access to the download page and we can search for the right data. Figure 2: The red arrow shows you where to click. 3. Search for the box (S010E090_N020E120) (Indonesia) and press on it. You can find the right box, in red, in the figure above this sentence. 4. Now we click on the box between the coordinates as shown in figure 3 (E95_E100 / N20_N15). Figure 3: The red box shows you where to click.

5 * Finally, we will get this image. It is important to see this area, because this will be our project in this document. Figure 4: The red arrow shows you where to click. At this point we can press the orange button with Download on it and save the data in a new map (DLT_Nyaungdon). 5. Unpack the zip file NO17E095 and open ArcGIS In ArcGIS, Press the button Add Data and connect the right folder by the button Connect to Folder. Figure 6: Add Data Figure 5: Connect To Folder 7. Now, open the folder NO17E095 and AVERAGE. You can see several files. It is important you open the following file: N017E095_AVE_DSM.tif. This is the largest file and contains the most information. At this point the data of Nyaungdon is imported in ArcGIS. The data needs to be sorted, before it provides you a reliable elevation map. The following steps will lead to the elevation map of Nyaungdon.

6 Create an elevation map by using the program ArcGIS 10.1 * The explanations of: Fill, Flow Direction, Flow Accumulation and Raster Calculator are quotes from this page: For more information about those steps you can click on the link above this sentence. You can find a download link and installation guide of ArcGIS 10.1 here: 1. Press the option customize a. Now open extensions. b. It is important the box Spatial analysis (figure 7) is selected! c. Finish by pressing the button close. Figure 7: Select Spatial Analyst 2. Now, open the ArcToolbox (use figure 8 and 9); a. Maximize the option Spatial Analyst Tools and the option Hydrology ; b. Finally choose the option fill. Figure 8: Location of ArcToolbox Figure 9: Where to find the option 'fill'

7 3. Choose in the option Input surface raster : N017E095_AVE_DSM.tif (use figure 10); a. Save this option as Filled in a new map named: Spatial analysis ; b. Press OK. Figure 10: How to use the option fill * The explanation of how the function fill works: Sinks (and peaks) are often errors due to the resolution of the data or rounding of elevations to the nearest integer value. Sinks should be filled to ensure proper delineation of basins and streams. If the sinks are not filled, a derived drainage network may be discontinuous. 4. Now choose the option Flow Direction in the map Hydrology (use figure 11); a. Choose as Input surface raster the file Filled ; b. save this step as Flow Direction. Figure 11: How to use the option Flow Direction * The explanation of how the function flow direction works: The direction of flow is determined by the direction of steepest descent, or maximum drop, from each cell. Figure 12: Flow Direction in ArcGIS 10.1

8 5. Now choose the option Flow Accumulation in the map Hydrology (use figure 12); a. Choose as Input flow direction raster the file Flow Direction ; b. Save this step as Flow_Acc. Figure 13: How to use the option Flow Accumulation * The explanation of how the function flow accumulation works: The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. If no weight raster is provided, a weight of 1 is applied to each cell, and the value of cells in the output raster is the number of cells that flow into each cell. For further explanation use figure 14. Figure 14: How flow accumulation works

9 6. Now open the option Map Algebra and choose Raster Calculator (for location use figure 16); a. Fill in the next sentence: Flow_Acc >= 1000 (use figure 15); b. Save as FlowAcc1000. Figure 16: How to use the option Raster Calculation Figure 15: Location of Raster Calculator * The explanation of how the function flow accumulation works: The Raster Calculator tool is specifically designed to offer the following benefits: Implement single-line algebraic expressions; Support the use of variables in Map Algebra when in ModelBuilder; Apply Spatial Analyst operators on three or more inputs in a single expression; Use multiple Spatial Analyst tools in a single expression. 7. Repeat step 6 a. Fill in the next sentence: Flow_Acc >= b. Save as FlowAcc10000.

10 8. Now we will chance the colors inside the map (use figure 17, 18 and 19). a. Double click inside the Table of Contents on the colored box 0 under FlowAcc b. Chance the Fill color into No color. c. Double click inside the Table of Contents on the colored box 1 under FlowAcc d. Chance the Fill color into Lapis Lazuli color. e. Double click inside the Table of Contents on the colored box 0 under FlowAcc1000. f. Chance the Fill color into No color. g. Double click inside the Table of Contents on the colored box 1 under FlowAcc1000. h. Chance the Fill color into Big Sky Blue color. Figure 18: Symbol Selector Figure 17: Table of Contents Figure 19: Result of those actions

11 9. Now unselect Flow_Acc and FlowDirection in the Table of Contents (use figure 20); a. Double click on Filled in the Table of Contents ; b. Choose the tab Symbology ; c. Select under the table Show : the option Classified ; d. At this point we can make an elevation map categories and colors decided by ourselves. Figure 20: Layer properties 10. Open Classify ; a. Choose 32 Classes ; b. Fill in the following numbers (as in figure 21) under Break Values ; c. Press OK. Figure 21: Range of break values

12 11. Choose a color Ramp (I use the colors red till blue) and flip the colors by click right on a number and choose Flip colors. Figure 22: Flip Colors At this point you have made a reliable elevation map of Nyaungdon as shown in figure 23. Figure 23: Elevation map of the area of Nyaungdon