Shauna EwaldNov 2 2017

GIS4850Lab 8

BackgroundSuppose you are hired by a mobile phone company to conduct a GIS-based site assessment to maximize their network coverage. How can we model topographic features to find locations for cell phone towers? We’ll incorporate suitability analysis, cartographic modeling, and surface modeling (relative radiance modeling) into this lab. The data that you will work with include the digital elevation model (in meters), census demographics at the Tract level.The goal of today’s lab is to create a model of four cell towers with the most coverage.

Part 0. Set up for your analysisUnder Geoprocessing > Environments, set your Workspaces to your Lab7 folder, and your Processing Extent to “Same as layer ELEVATION”.In File > Map Document Properties, check “Store relative pathnames to data sources”.

Part 1. Work Breakdown Structure (WBS)As consultants, your first step is to create an estimate of the time and expense on the project. To do this, you will create work breakdown structure that breaks your team’s work into smaller tasks. A WBS is simply a list of the tasks needed to complete a project. In project work, you would use this to guide how you assign tasks and plan for expenses and time.

1. Create a Work Breakdown Structure for this project. (1.0 points)

1.0 Cell Tower Identification Project Background1.1 Collect Data

1.1.1 GIS input1.1.1.1 Elevation Layer 1.1.1.2 Tract/Population Layer1.1.1.3 Counties1.1.1.4 Cell Tower

1.1.2 Radiance (altitude/azimuth) input1.2 Setup for Analysis

1.2.1 Create toolbox 1.2.2 Create model

1.3 Model Topography 1.3.1 Extract Elevation layer to mask 1.3.2 Create contour layers1.3.3 Create Slope1.3.4 Create Aspect1.3.4 Create Hillshade

1.3.4.1 Time (3)1.3.5 Create Viewshed

1.3.5.1 Cell_Tower11.3.5.2 Cell_Tower1 with height

2.0 Cell Tower Identification Project2.1 Collect Data

2.1.1 GIS input2.1.1.1 Elevation Layer 2.1.1.2 Tract/Population Layer2.1.1.3 Counties2.1.1.4 Cell Towers (4)

2.1.2 Radiance (altitude/azimuth) input2.2 Setup for Analysis

2.2.1 Create toolbox 2.2.2 Create model

2.3 Model Topography 2.3.1 Extract Elevation layer to mask 2.3.2 Create Slope2.3.3 Create Aspect2.3.4 Create Hillshade

2.3.4.1 Hourly radiance (11)2.3.4.2 Mean radiance (1)

2.4 Reclassify Topography2.4.1 DEM (5 breaks – top break)2.4.2 Slope (<5%)2.4.3 Aspect (No North)2.4.4 Mean radiance (top quartile)

2.5 Raster Calculator2.5.1 Possible Site Locations (T/F)

2.6 Choose Locations (4 Cell Towers)

2.7 Viewshed Operation2.7.1 Cell Tower Viewshed (4)

2.8 Raster Calculator2.8.1 Add Layers

2.9 Reclassify2.9.1 (T/F) viewshed occurance2.9.2 (highest total) best view

2.10 Tracts (pop2010)2.10.1 Calculate pop from Viewshed mask

Part 2. Modeling Topography

➢ Setup your data by using the Extract by Mask tool with the ELEVATION layer as your input raster and the COUNTIES layer as your “feature mask”. Use this output for the rest of your tasks needing a DEM. ➢ Use the Contour tool to create a contour layer based on the DEM (base contour = 5000; contour interval = 250). ➢ Create a Slope and Aspect layer based on the DEM layer as well. ➢ Create a shaded relief map by using the Hillshade Tool (azimuth = 160; altitude = 30).

2. Make a NICE map for your Hillshade layer. (1.0 points)

Part 3. Modeling Relative Radiance

Next, we will find out the relative radiance of the Sun’s irradiance at daybreak along the Front Range. The relative radiance is the amount of sunlight that is hitting the surface of the earth. We can do this using Hillshade and setting the angle and direction of the sun.

Use Form A to find out relative radiance by using the following parameters:

o Object: Sun o Time: October 13, 2015 o Tabular Interval: 10 o State: CO o Place Name: Denver

What is the sun’s azimuth (direction) and altitude (angle height) at Denver after sunrise (i.e. the first 3 pairs with positive altitude)?

o Time: _7:10_ Altitude: _0.1_ Azimuth: _99.8_o Time: _7:20_ Altitude: _1.8_ Azimuth: _101.4_o Time: _7:30_ Altitude: _3.5_ Azimuth: _103.0_

➢ Use the DEM extract layer and three iterations of the Hillshade tool to model the Sun’s altitude and azimuth based on the three pairs shown above. ➢ Use Cell Statistics tool to find the mean (average) of these three Hillshade results.

3. Make a NICE map showing the mean Hillshade from this last step. (1.0 points)

Part 4. Cellular Tower Assessment➢Create the viewshed by using the Viewshed tool with the DEM as the input raster and the Cell_towers layer as the input point. Observe the resulting new layer. ➢ Add a new field (type = double; precision = 10; scale = 3) in the Cell_towers attribute table named “OFFSETA”. ➢ Fill in the value for this new field as 30 using Field Calculator. This represents an offset height of 30 meters for this point feature. ➢ Create the Viewshed again with the DEM as the input raster and the tower1 layer as the input point as before and compare the resulting layer.4. Make a NICE map showing your initial Viewshed from the last step. (1.0 points)

Part 5.

5. Report the hourly relative radiance of the Sun’s irradiance in Denver, Colorado on October 13, 2015 between sunrise and sunset (i.e. ignore any negative altitudes) using the website in Task 2. List the sun’s azimuth and altitude in a table using the following format: (.5 points)

Time Altitude Azimuth07:00 -2.3 98.208:00 9 10809:00 19.5 118.710:00 28.9 131.411:00 36.5 146.612:00 41.3 164.713:00 42.3 184.614:00 39.4 20415:00 33.2 220.816:00 24.7 234.717:00 14.7 246.318:00 3.9 256.519:00 -7.7 266.1

6. Make a NICE map of your mean daytime relative radiance. (1.0 points)

7. Take a screenshot of your model and include it in the word document. (1.0 points)

➢ Turn on the TRACTS layer. Create a dot density map using the symbology tab in the TRACTS layer (Value=POP2010).

➢ In ArcCatalog, create three new Cell tower point layers – Cell_tower2, Cell_tower3, and Cell_tower4. ➢ You can move the cell towers if you need to in order to achieve a better coverage.

➢ For each Cell_Tower layer, add a point (4 cell towers in total) based on your visual examination of the original DEM, slope and aspect (as needed) and most importantly the population pattern. Your overall goal is to cover more than 50% of the area and 75% of the population. Each tower is allowed a maximum height of 30 meters.

➢ Open the attribute table for each of your four viewshed layers from your four cell towers. How many cells can each tower see? Calculate the area using the following formula: Area = (cell size) X (cell size) X (Number of cells) = . (27.36953143) * (27.36953143) * (x) =

8. Report the coverage of the cell towers using the table below. (1.0 points)

Tower Number of False Cells

Number of True Cells

Equivalent Area (m2)

50% area Total Population

Cell Population 75% Population

1 1111576 377056 282449350.62 828269 321012 240467280.63 711440 437841 327982862.34 768708 380574 285084653.6View_Total 576874 572407 49.8% 2489661

9. Create a formal map with all proper elements representing the total coverage area of the 4 proposed cellular towers by using Raster Calculator to produce an addition layer. Where is the area of best coverage?

What is the best overall strategy in locating a good location for cellular tower? (1.0 points)

Reclassify the Mean Hillshade with the top quartile being true. Reclassify the DEM into five different elevation groups. Combine those maps with Raster Calculator to find where the sunniest and highest elevation cells. Low slope and southern aspect input is optional. Two towers (3&4) provide coverage for the northern half extending to the east. Two other towers (1&2) are covering the southern half with one more responsible the mountainous part.

10. Why would the average radiance that a location receives help to determine the best cell tower position? What does the Hillshade function calculate? (1.0 points)

The Hillside function creates a shaded relief map from calculations based on the sun’s location. So, it calculates shadows. If a cell tower is in a shadow, then it implies it is in a geographic depression. Cell signals will be blocked from the neighboring elevation if the tower is in a depression. So, the best place for a tower would be in an area with the least amount of shadow. The average radiance map eliminates shadows created in both morning and evening.

11. Feedback – answer the following questions: (.5 points)

a. How long (in hours and minutes) did this lab exercise take for you to complete? 6-7 hours

b. What did you like about this lab exercise? Hillshade isn’t just a visual cue.

c. What did you find difficult? Where did you get stuck? I moved the cell towers many, many times to try and cover 50% of the study area. At first I tried to keep tower locations within slope and aspect parameters as well but I gave up on that. I tried to find a way to measure population in the final coverage output, but I gave up on that too.

d. Were there errors written in the exercise that inhibited your ability to do the work? If so, did you ask for help? From whom? I don’t know if it’s an error, but modeling the average hillshade operation gave the correct output, but when re-using that output as in input for the Cell Statistics tool I didn’t trust that I had 11 inputs as I could only see one. Opening the Cell Stats tool in ModelBuilder showed only one input with multiple outputs when what I wanted was the opposite. So I went ahead and modeled 11 separate inputs into Cell Stats.

e. How might you use modeling and surface analysis in your project? Slope is definitely being used. Hillshade might be used for soil moisture measurement purposes.

f. How did you work match your Work Breakdown Structure? Not much. Here’s the final model: