USING GEOMEDIA 3D: HOTSPOT DETECTION AND VISUALIZATION

Transcription

1 USING GEOMEDIA 3D: HOTSPOT DETECTION AND VISUALIZATION etraining Introduction Use GeoMedia and GeoMedia 3D for hotspot detection and visualization. Software GeoMedia and GeoMedia 3D Data QuickBird-2 image of Prescott, NV Transcript 0:09 0:25 0:45 1:06 1:29 Welcome to Hexagon Geospatial etraining: Our topic is an Introduction to GeoMedia 3D. In this module, we will explore how to use a collection of GeoMedia and GeoMedia 3D commands for Hotspot Detection and Visualization. Hotspot detection is an approach that is ideally suited for extracting geographic concentrations from sparse data sets. For example, this technique can be used to locate hotspots within datasets containing epidemiological pandemic events, law enforcement crime events, utilities outage events, or transportation accident events. In this example, the Hotspot Detection command in Incident Analyst was used to identify areas containing a large volume of 911 calls for a specific week. This map was used by authorities to implement a directed patrol protocol; in essence, the protocol was designed to proactively direct field officers where they were most needed given a specific time slice. Hotspot maps can come in a variety of forms. For example, they can be in the form of a statistical surface where color and cell values are used to reflect hotter and cooler areas. The output of the Grid > Density command is visually attractive and helps to invoke further investigation and exploration for the reasoning behind why incidents are concentrated in some areas. Hotpot maps can also include additional map elements such as isolines. As can be seen in this slide, the Grid > Surface > Isolines command could be run using the density surface as input to better delineate discrete zones within the density surface.

2 1:45 2:11 2:31 2:41 3:00 A hotspot however is actually defined as a center of high activity within a larger area of low activity. These types of maps are extremely useful because they distill complex information into a simple picture that almost any map reader can understand. These maps are therefore effective intelligence resources for public education. The map represented in this slide was created using the Grid > Classification > Hotspot Detection command. These representations are all very nice; however, when 3D is brought into the equation, the overall appearance of your map will provide the map reader with additional insight because not only do the hot areas stand out because of the color, but they also pop out because of their height. Let s see how to create this in GeoMedia. As you can see, GeoMedia has been launched, a Geoworkspace is open, and we re already in a 3D view. Therefore, we can easily roam across the data. The yellow pins on the screen represent incident locations. These yellow pins have been stylized to represent the number of incidents or occurrences at each location where: one occurrence is represented by the smallest pins, two occurrences are represented by the medium sized pins, and three occurrences are represented by the largest pins. The first step in the workflow is to create a density surface to better represent the distribution of the incident locations. More specifically, to identify areas where both incident occurrences and clustering are higher than normal. 1. To do this, from the Grid tab select Interpolation > Density to open the Density command. 3:19 This command takes the incident locations as input and then creates a two-dimensional array of pixels that reflects both proximity and intensity (or in this case the number of occurrences). 2. Open the Point Feature drop down menu, expand Points and select Incidents. 3. Set the Intensity attribute to Occurrences. 4. Type Density Surface as the Density layer name. 3:43 The default fixed bandwidth is used; however, the command includes an adaptive bandwidth option. When this option is enabled, the kernel size changes dynamically to reflect localized clustering and thereby produces hotspots that more closely hug the data that is clustered. 5. Click OK to run the command.

3 4:02 Once the command completes, a black-through-white grid layer is automatically displayed in the 3D view, on which the lighter pixels represent the hotter areas. This default representation is okay: however, visualization is an important part of understanding these types of results, and the use of color can help the map reader better interpret the results. 6. To change the color, select List. 7. Expand Hotspots, right click to open the menu and select View Legend. 4:29 In this case, the grid legend is used to create and apply a dark-blue-through-red color sequence. 8. Select all of the points, right click and select Color Sequence to define the new colors. 9. Set the color on the left to dark blue and the color on the right to red. 10. Note that the distribution of the color sequence is set to Change in zone value. With this option, the greatest change in pixel values causes the system to apply the greatest change in color, thereby highlighting these areas. 11. Click OK and Apply and close the dialog. 12. Close the Study Area dialog. 5:06 Once the color sequence has been applied, the blue pixels now represent the cooler areas, where the red pixels now represent the hotter areas. 13. Use the navigation tools in the top right of the viewer to adjust the view. 5:19 5:35 When you tilt the view you can easily see how the Density Interpolation command has not only taken proximity into account, but also the intensity. In this case, the grid layer is at the top of the display stack in the legend, and as a result, it s obliterating the underlying data, the aerial imagery. GeoMedia can be used to stylize grid layers or raster images. 14. Double click on the Density Surface layer to open the Legend Properties. 15. Set the Translucency to 50% to decrease the opacity, and allow the data from the aerial imagery to bleed through and provide context. 16. Click OK to close the dialog. 5:53 This representation of the hotspots is nice, but with 3D, its representation can be improved by taking advantage of the third dimension. This can be done by using the statistical surface as a terrain layer.

4 6:05 We ll use the Manage Surface command to do this. 17. From the 3D tab, select Manage. 18. Change the Display option to On and close the dialog. 6:16 6:41 7:01 7:13 Notice that GeoMedia 3D reacts immediately upon user feedback and updates the view. Specifically, the 3D view now includes the Density grid layer as a terrain surface, and the pixels representing the hot areas are now also higher in elevation. This type of 3D visualization provides the map reader with additional insight into the dataset because the hot areas not only stand out because of the color, but they also jump out because of their height. GeoMedia 3D includes a complete set of flight path commands that allows you to create, edit, and fly flight paths. Here we are showing an example of a predefined flight path to fly a route that effectively shows the results of our work. Flying a predefined flight path as we see here, can be extremely useful in better understanding the data. The workflow thus far illustrates how 3D can be used to visualize density data that is derived from a collection of points. However, we really don t know where the hotspots are, and a statistical approach is needed. To extract hotspots from this data, the Grid Hotspot command is used. 19. On the Grid tab, select Classification > Hotspot Detection. 20. Set the Source Layer to Density Surface and the Multiple of Mean to Click OK to run the command. 7:31 7:45 Once all the parameters have been specified, the system automatically places the results in context and the 3D view updates accordingly. Notice the dark red areas. These areas represent the statistically extracted hotspots. The Hotspot Detection command created a grid representation of the hotspots. These again look very nice and are statistically valid; however, having these areas isolated as an area-based feature class can be extremely useful. Specifically, once isolated and stored as a feature class, the polygons can be used within spatial queries.

5 8:05 We ll make some adjustments to better visualize the next step. 22. From the Surface group on the 3D tab, select Manage. 23. Set Display to Off to deactivate the statistical surface as a terrain layer and click Close. 24. To vectorize the data, select Grid > Vectorize to Feature. 25. Select Hotspot of Density Surface and set the Conversion type to Area. 26. Place a checkmark next to Simplify output feature. 27. Leave the other defaults and click OK to run the command. 8:37 8:51 In this example, an area-based feature is created and stored in the feature database so that it can be used at a later time. Once the command completes, the Density Surface layer and the Hotspot layer are removed from the view because they re no longer needed. With the 3D view cleaned of all previous results, the GeoMedia Legends command can be used to add the vectorized version of the Hotspot layer to the view. 28. From the Home tab select, Legends > Add Legend Entries. 29. Expand Points and select Hotspot of Density Surface_V1, and click OK to add it to the view. 30. Double click on the Legend key to open the Legend Entry Properties. 31. Change the color to Red with a transparency of 45% and click OK. 9:19 9:24 We can now see the red areas that represent the Hotspots. Thank you for watching this etraining module from Hexagon Geospatial. For more etraining, please visit hexagogeospatial.com/etraining.