Mapping Hacks

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Chapter 6, Mapping on Your Desktop

#65 Extract Data from Maps with Manifold

HACK

The population of Varna, as defined by the plan noted earlier, is 679 peo-

ple, according to the 2000 census. (Because Manifold adds all the values, the

averages included in the data don’t come out so well and need to be recalcu-

lated.) One final nice touch is that you can combine the new drawing with

Figure 6-14. Data being pasted

Figure 6-15. Varna’s census blocks, isolated

Extract Data from Maps with Manifold #65

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HACK

the old one to create a map that highlights the area chosen for calculation.

In Manifold, go to File

➝ Create ➝ Map..., and select the two drawings, as

shown in Figure 6-19.

Open the map you’ve created and then right-click on the tab for

“Tgr109blk00s Drawing.” Choose “Opacity...” from the menu that appears,

and set it to 30%. If you then zoom in a little, you’ll see the darker Varna

area standing out against the surrounding blocks, and the divisions for the

blocks it contains are still visible, as shown in Figure 6-20.

Figure 6-16. Choosing a field for dissolving boundaries

Figure 6-17. Varna census blocks dissolved into a single object

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