Viewshed Analysis of Cell Towers

            Cellular signal strength in any location in Los Angeles County is important in daily life for modern day society to progressively make connections with each other. The operation of cell phones is dependent on cell tower location, height and power. Conducting viewshed analysis on cell tower coverage for Los Angeles County allows further determination of which dependency best enhances cell tower performance and produces higher population receiving signal. The original viewshed is shown, along with re-conducted viewsheds with unique added options to analyze the differences when compared percentages between original and new.

            The DEM for Los Angeles County and surrounding areas was downloaded from the USGS Seamless website. Two separate DEMs had to be connected by mosaic. This output mosaic DEM projection was then converted to WGS 1984 UTM Zone 11. The cell tower layer projection was kept the same. Instead, new attribute fields were added: OFFSETA, OFFSETB, AZIMUTH1, AZIMUTH2, VERT1, VERT2, RADIUS1, RADIUS2. OFFSETA represents the height of the cell towers and was set to 30 meters. OFFSETB is the height of the cell phone user (1.4 meters). The range for AZIMUTH values was set from 0 to 360 and VERT from 90 to -90. RADIUS1 and RADIUS2 indicate the power of the cell towers and were set from 0 to 30,000 meters respectively. An important note is to set both OFFSETA and RADIUS2 as long integer when calculating with field calculator. Also, OFFSETB is set to float since it’s a decimal. Before running viewshed analysis, one last step was to lower the resolution for the mosaic DEM. Using the aggregate tool, the DEM resolution was changed from 30 meters to 90 meters. The cell factor had to be set to 3 (3 times 30 meters is 90). Check for spaces that might distract the viewshed analysis process and fix each folder in the storage drive to avoid errors. Now, the viewshed can be run between the cell tower and DEM layers. A hillshade of the DEM was also created to show elevation texture. The viewshed output was moved on top of the hillshade and the transparency of the viewshed was increased to 60% for clarity. The last procedure is to extract by mask to obtain values in order to calculate percentage for reception potential within Los Angeles County only. Extract by mask was done between the viewshed and a separate Los Angeles County clipped boundary layer. Different viewshed analysis tests following the same procedures mentioned above was conducted.

Given $30,000 to determine how cell tower performance can be improved, several steps were taken. One, 3 new towers were added using the Editor tool to locations of lowest cell reception. Two, the height of all cell towers were raised by 10 meters. And three, the power of each tower’s range was raised by 5,000 meters. Before conducting the second option viewshed analysis, the newly added points were removed and data values for OFFSETA were changed. Similarly, before conducting the third option, OFFSETA values were changed back to its original values and RADIUS2 was changed. Lastly, extract by mask was conducted for each. Percentage calculation of how much reception is available to people in Los Angeles County proves that cell tower power is important. Increasing the radius by 5,000 meters generated a percentage of 62% of the population receiving signal. It is only a 3% improvement from the original viewshed analysis, but it proves to be the best solution for increased reception. Adding 3 extra cell towers at optimal locations generated a percentage of 59.9% and raising the height of each tower resulted in a percentage of 61%. The algorithm of the calculation is to take the sum of the total number of people receiving reception from the attribute table of the extract by mask layer. Then, dividing this value by the total population in Los Angeles County and multiplying this resulting value by 100 to obtain a percentage. Increasing power is recommended. Therefore, further power increasing is suggested, perhaps increasing higher than just 5,000 meters more.