Find all Regions visible from the top of a 100 foot Tower

This topic comes from the case files of Manifold Technical Support. A customer is using Manifold System Release 4.50 and Manifold 3D View Studio. The customer is having difficulty using multiple maps in the workspace and is attacking the learning curve for Manifold and 3D View Studio simultaneously with a specific task in mind. Time for reading Help topics is very short.

The Finding and Saving Visibility Zones topic in 3D View Studio Help appears to be unhelpful because it presumes familiarity with Manifold System. Because the customer is new to Manifold as well, a highly detailed step-by-step example is required. Tech Support swings into action....

Customer Question: What I am trying to do, it to locate one 100' tower on a relatively higher elevation and find out what areas are within the line of site of the top of the tower for 360 degrees up to 20 miles away. I would like to present the map as a 2D map with a notation representing those areas that are visible from the top of that tower.

	Launch Manifold and open the Az.mfd map. Turn off all layers except Roads, Hydrography and Boundaries.
	Use Insert - Map to insert the ajo-3.mfd map. Drag the ajo-e tab all the way to the left in the layer tabs so that it is easily visible. Here, we have right-clicked onto the ajo-e tab and chosen Replace Selection to place all of the ajo-e points in the selection and also recolor them in red.
	Here we have used Zoom Box to zoom into the ajo-e points. Note how the rectangular grid arrangement of points characteristic of a DEM is obvious.
	Launch Solvers - 3D View - 3D View Studio (Points Only) using the selection as the point set and the [Elevation] field for elevation.
	Manifold computes for a bit and then opens the main 3D View. Here it is zoomed in (up arrow on the keyboard) and tilted a bit (click and drag up and down with the mouse). We are opening the Analyst console.
	The first job in Analyst is to add a Point using the Locations function.
	Click into the center of the preview panel to place a + cursor there. The coordinates and height of the place we picked will appear in the readout boxes. If we don't like this exact place, we can change the coordinates to whatever we desire. Note the Z value. Iin the illustration, 749.7 ... let's call it 750. We want a location that is 100 feet higher, so we change the Z value to 850.
	Press the Point... button and choose Add. A point in the designated color appears at this location. Click on the Result button and choose Add as Element. This creates the point as a 3D element which can later be imported into Manifold. It also gives us an element that we can edit in the 3D View to create a cool line showing where our tower is, etc.
	Change the Function to Sight Zones and check the box for 1. Point in the Locations pane. Press Update. This computes the zones visible from the location we set earlier. If we want greater accuracy, increase the Quality factor. Press Result and Add as Element to create a 3D surface representing the visibility zones.
	Here is 3D View showing the Point and the visibility zone. We've colored them more brightly using the Elements panel to make them visible. The visibility zone looks a little choppy because we used a low Quality of only 15. Increase the Quality if you desire. (Do it in small steps if you have a slow system).
	In the main 3D View menu, choose File - Save and save the file as visibility.m3s Exit 3D View Studio.
	Back in Manifold, create two new layers called tower and visible. Click on the visible layer tab to make it the active layer. Choose Solvers - 3D View - 3D View Studio Import . Choose Add and open the visibility.m3s file in the Open dialog. Check the Sight Zone object and uncheck the other boxes. Press Import. The sight zone object will be imported.
	Click on the tower layer tab to make it the active layer. Repeat the above step, but this time import the Analysis Point.
	Here we have zoomed in slightly into the DEM data set, and we have changed the color and size of the tower point, and we have changed the area style used to show the sight zone, using blue for foreground color and no color for background color to get a "transparent area" effect. Let's do something about those ugly DEM dots.
	Note that the contents of the ajo-e layer (the DEM points) are still selected. Click on View Table as Selection and click on the Elevation column head to sort the table by elevations. It ranges from 200 something to 1200 something, so 700 is about in the middle. Load the SQL toolbar with [Elevation] >= 700 and push Select to select all of the DEM points above 700. Push in the Format Selection mode button and Format Points buttons, then push the Format button and set up the Format Objects dialog as shown. (We're using "no color" for the background color). This will color all the selected points in green using a diamond shape. The screenshot shows the display just after we have pressed Apply in the Format Objects dialog.
	Here we selected all the ajo-e points that were less than 700, saved them to a new layer called low points and double-clicked on the layer tab to turn them off. That makes for a cleaner display that shows just the "high ground" as green diamonds overlaid with the visibility zones.
	Take a moment to use Tools - Projections to project the map. We've used Lambert Conformal Conic (LCC) with parallels of 25 and 45, and latitude origin of 35 and longitude origin of -112. The three illustrations at left (added after this case study was finished, so they not the same workspace as the other illustrations, but similar) show the projection process. 1. Place the cursor in the middle of the area of interest. Note that it is at approximately latitude 32, longitude -112. 2. Run Tools - Projections using reasonable values. The latitude/longitude origin values should be about the center of the area of interest. First and second standard parallels in the LCC aren't critical, but should not be too far above or below the area of interest [ideally, they should cut through the area of interest about one fifth down from the top and one fifth of the way up from the bottom, but, what the heck...] 3. The result is a projected map in Lambert Conformal Conic. Note: make sure to remember to use a minus sign in front of longitudes in the Western Hemisphere, and a minus sign in front of latitudes in the Southern Hemisphere.
	Here we have created a new layer called circle. We've clicked off various layers to simplify the display. We've turned on snap to points so we can easily snap to the tower point, and then we launched the Solvers - Utility - Make Objects - Make Circle solver. We clicked on Center and then clicked on the tower point. Note the boxes checked to create lines and create areas. Press OK.
	This creates a circle that is 20 miles in radius from the tower point. We've changed the formatting of the circle so it appears as a "transparent area style".
	We've now selected the visibility zones area and have used the 20 mile radius circle area to Clip Inside the visibility zones. We've placed the result in a new layer called clipped zones. The Clip Inside solver is part of the free Topology Plus solver package that may be downloaded from the web site.
	Some people might not like the "triangulated" style of the areas produced by the import of the sight zone. Here we have selected the clipped zone and have created Centroids, which have then been formatted into little yellow boxes. If you create sight zones using a higher quality factor in 3D View Studio, you can have plenty of dots or other symbols showing the visible area.
	Turn on the Legend window from View - Legend. Click ON Snap to Points and right-click onto the tower point and choose Add object to Legend from the pop-up menu.
	Repeat this for the "high ground" points and for the little yellow boxes. Turn OFF Snap to Points and then right-click onto the circle area, add it to the legend, right click onto the visibility zone area and add it to the legend.
	Click on the top line in the legend and then right-click anywhere in the legend and choose Add Heading. Add a heading text. Right-click in the legend and choose Add Blank Heading to put a blank line between the heading and the body of the legend. Double-click into the various legend text items and change them to something informative as shown. Note: make sure you have SP2 installed to fix the legend bug that sometimes blanks out headings on certain edit operations. Use Insert - Text Label to insert some labels. Right-click onto a label and choose Format Label to change its formatting if desired. Don't forget to turn OFF Insert - Text Label when done adding labels. Move labels around by clicking and dragging them. [Works if the cursor is not occupied by being in the middle of a different command...]. We've also formatted the Az map a bit, zoomed in and changed the background color. There... that's better!

Conclusion: The actual visibility zone analysis is a one click step, as pretty much are the import. Virtually all of the above was mostly formatting and moving objects between layers and turning layers on and off to make formatting easier.

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