Buffer Zones and ViewBots Tour

This tour is an abbreviated version of the full Buffer Zones and ViewBots step-by-step example in the Release 4.50 User Manual.   The tour provides a "photo gallery" sequence of images without all of the command detail.

The example: we have an insurance company with customers located near shorelines in St. Petersburg, Florida. We wish to know how much money we have at risk for customers within 2 miles of the shoreline.

Load the USGS map of Florida from the Manifold CD.

Project it to Lambert Conformal Conic projection.

Display Hydrography Layer

Use SQL Toolbar to select [Hydrography Options] = Shoreline. This selects the shorelines:

Save the shorelines to a new layer and zoom in to St. Petersburg area (blue box).

We now are zoomed in to the St.Petersburg area of Florida.

Step 2: Merge Customer Data into the Map

We merge our geocoded customer database (green dots) into the map.  Each customer has an At Risk field showing the amount of the policy.

Select the shorelines in the St.Petersburg peninsula.

Run the Buffer Zone solver using the selection, with buffer zone set to 2 miles.

Use SQL Toolbar to select all the customers within the buffer zone.

All of the Customer points Within the buffer zone have been selected and highlighted in red. They may now be used in any solver operation. For example, we can run the Solvers – Statistics – Simple Statistics solver using the selection as the object set and the At Risk field as the formula:

This solver reports to Results History a collection of simple statistics for the chosen field.

At a glance we can see the information on the At Risk values that fall within the 2 mile buffer zone. The mean value of At Risk, for example, is 432.32.

Step 5: Adding ViewBots

ViewBots provide an easy, interactive way of seeing statistics and other aggregate functions. Click open a ViewBot, configure it by telling it what scope to watch and what function to compute, and it will automatically compute that value even if things change in Map View.

We will open three ViewBots. These will look at the selection and report the total value, the maximum value and the minimum value of the At Risk field to be found in the selection.  Click the Add ViewBot command to add a ViewBot and then click on the "i" information icon in the ViewBot's toolbar to customize it.

Enter the values as shown above in the properties dialog. This ViewBot will look at the selection, and will report the sum of the At Risk field. The Heading gives the text we wish this ViewBot to use to report the result.   Here's how the ViewBot will look:

We will repeat the above process to create two more ViewBots. One will report the Maximum of the At Risk field while the other ViewBot will report the Minimum of the At Risk field.

The result is three ViewBots floating in Map View that constantly report these three parameters for the At Risk field for points in the selection:

Here is a close-up illustration of the ViewBots. If we change the selection, the ViewBots will automatically update the values they report.

The magic of ViewBots is that once they are added there is nothing to do. One simply makes whatever selections are interesting and the ViewBots automatically will report their functions for the selections made. This works whether we've told our 'Bots to watch the selection, watch a particular layer, or to simply watch all the objects that happen to be visible in Map View.

Right-click on the Customers tab and then choose Replace Selection in the pop-up menu. This selects all of the customer points.

The ViewBots will automatically update to report the new values.

Let's use the SQL Toolbar to select all of the customers that are not in the buffer zone:

Again, the ViewBots will automatically update to report the new values.

As fast as we can make a new selection, the ViewBots will report results based on that selection. This makes it possible to examine data through visual selection yet always have a statistics measure immediately at hand. For example, suppose our insurance company is arguing with the City about the designation of a flood zone. We can select different possible layouts of the flood zone (say, for example, by drawing a free-hand selection box using Polygon Select) and automatically see the effect on our business interests.

The buffer zone area used in the example above extended over water from the shoreline as well as over land. Some users prefer to create a buffer zone that is a “land only” buffer zone so that their presentation graphics are simpler.

First, create an area for the land area of St. Petersburg.

Select both the land area and the buffer zone.

Run the Area Intersection solver to create a new area that's the intersection of the two:

Click OFF the original buffer zone and the St. Petersburg land area to simplify the display.  Turn the customer points back ON:

Note that the buffer zone we created above is an area just like the buffer zone that extended out over the water. We can use it to make selections with SQL Toolbar as we did the original buffer zone.

ViewBots are also very powerful and user-friendly to boot. In this example we told our ViewBots to watch the selection. ViewBots can watch other scopes, for example, a particular layer, the entire map or even all the objects visible in the current Map View. ViewBots provide many other aggregate functions in addition to the three (sum of, maximum, minimum) used in this example.

Although we did not do so, one might use Manifold’s Spatial Overlay capability to aggregate the value of the At Risk customer points field and assign it to the buffer zone. In a large map with many customers, one might create several buffer zones at 0.5, 1, 2, and 3 mile distances from the shoreline. Using Spatial Overlay one could then aggregate the values of the At Risk field for the customer points within each buffer zone to create a total At Risk value for each buffer zone. One could then auto-format the buffer zones in different colors to display for presentation purposes the relative risk of each to the insurance company.

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