GIS 4048 Module 7: Homeland Security - Protect MEDS

Figure 1: Military template map layout showing the 3 mile security buffer zone around the Boston Marathon finish line as well as checkpoints set wherever a road enters the 500 foot finish line buffer.

Figure 2: A map layout with multiple elements focused on 16 suggested surveillance points surrounding the finish line and how clear their view is of the finish line and environment.

The assignment for this week, the final module focused on homeland security and crime analysis, was to take the data collected, processed, and organized last week and use it in an analysis of security planning at the Boston Marathon finish line. The focus of the first map is the three mile security buffer zone created around the finish line. By using the Select by Location function of ArcMap with this buffer, we can find the potential targets of attacks near the finish line (including hospitals, schools, and airports). For the purposes of this assignment, we focused on hospitals. However, given the number of hospitals within the three mile zone (49 total), we looked only at the ten hospitals closest to the finish line. We used the Generate Near Table tool and joined the resulting table to the hospitals layer to see the distances of each hospital from the finish line. We then created buffers of 500 feet around these ten hospitals symbolizing areas requiring extra surveillance and security. The final task in the first map was to create a 500 foot buffer around the finish line and place checkpoints at each road as it enters the buffer. This was accomplished using the Intersect tool with the local roads and finish line buffer layers as inputs. The result was a layer with points at each intersection point.

The next group of tasks for the second map was to use LiDAR data to aid in the placement of surveillance points near the finish line. After exploring the provided LiDAR data with the LAS Toolbar, we used the LAS Dataset to Raster tool to create an elevation raster. We then used the Hillshade tool to create a hillshade layer from the elevation raster; the altitude and azimuth data we needed were acquired from http://aa.usno.navy.mil/data/docs/AltAz.php. This layer allows us to see the shadows that will be present at a particular time of day, in this case the time of the bombing. We next created a new point layer indicating several surveillance points around the finish line. The Viewshed tool was used in conjunction with this point layer to see the estimated visibility of the area from the surveillance points. To increase visibility, we added an OFFSETA field to the surveillance points layer to adjust the height of each point. The Viewshed tool was run several times with different point height variables until visibility increased significantly. To further check visibility from each point, the 3D Analyst toolbar was used to create lines of sight. This tool creates lines indicating areas that can be seen and areas that cannot be seen from one point to another. The positions of several points were adjusted based on this information. Profile Graphs of these visibility lines were also created from the 3D Analyst toolbar to better see how much the views were obstructed. Finally, ArcScene was used to create a 3D model of the finish line environment and the proposed surveillance points as well as their lines of sight. The elevation raster and orthoimagery layers were added (with their Base Heights variables adjusted accordingly) along with the lines of sight. This was to add another element to the final map layout to aid in visualizing the finish line's surroundings.

Overall, this was one of the most enjoyable modules of the course thus far. We worked through many steps and used many tools, but it gave us a taste of how GIS data are processed and used in real-world analysis tasks.