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We are creating a map of world time zones and have noticed that the base map used does not portray the Great Lakes. It simply shows the international boundary between the US and Canada. In this screen shot, we have just "cut out the southern, US portion of the Great Lakes. Note however, that in the northern part of the lakes the Canadian area extends to the international boundary and does not follow the Northern shoreline. Our task is to clip the Canadian area to the line followed by the shoreline. |
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Our
first step is to load a map showing shorelines. We do this with
the Merge Data tool to import an area into our map from a higher
resolution map. In this case, we have imported a high resolution
map of Ontario from the NTAD 99 Canadian provinces digital map.
We've used a transparent area style so that objects below the Ontario
province are visible. We can see in this screen shot how the
northern border of the Great Lakes needs to be cut out so that it
follows the shoreline and not the international boundary.
Because our base map is lower resolution than the Ontario province, the Ontario province does not overlap the lower map as a good "cookie cutting" area should do. We will build it up by drawing some new areas and adding them to the Ontario area using the Area Union solver. We can then use the new, built-up area as a handy cookie cutter. |
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We
move the Ontario area into a layer called tmp. We set the
default format for this layer to be a transparent area style in light
purple dotted pattern. We apply the default format so that the
Ontario area has this area too. Now, we zoom far into the
Easternmost region.
Using Snap to Areas we start drawing a new area where the Ontario area touches the Easternmost part of Lake Erie. We continue drawing the new area "free hand" by pressing the Shift key to defeat the Snap to Areas when we don't want to snap to the nearest area. In a few seconds, we've drawn a new area. The new area overlaps the original Ontario area. |
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Now we zoom out The area we just drew is visible at the Easternmost end of lake Erie. We will now draw another, larger area that overlaps both the original Ontario area and also the new area we drew in the previous step. We are drawing areas in two steps because if we zoom in far enough for really good precision in the first area, the map area visible in the screen is too small to draw a big enough area for convenient usage in later steps. Drawing areas is so fast in Manifold that it's a simple matter to draw a little area at very high zoom and to then zoom out and draw a bigger one which will be used in later steps. |
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Let's now pan over to the Western border of Ontario in the Western region of Lake Superior. Here we draw a new, big area that overlaps the Ontario area. |
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We now zoom enough out so that the entire Ontario area is visible. We now draw a very large area that overlaps the Ontario area as well as the new areas we built up to the East and West parts of the Great Lakes. It's now apparent why we built up the the areas: working at a large enough zoom to see the entire Ontario area, it's difficult to click precisely on very minute variations of the Ontario area near the Easternmost shoreline of Lake Erie or the Westernmost shores of Lake Superior. By creating areas in those places at much higher zoom we give ourselves convenient targets that are easy to click on when creating this big area. |
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Here is the new area we have created, together with all of the previous ones. We will now use the Area Union solver to join all of the areas in the tmp layer into one big area. |
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Here we have selected all areas in the tmp layer and have launched the Area Union solver. |
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Voila! The new, unified area. We will use this big area as our cookie cutter to split the underlying Canadia province area. |
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We select the underlying Canadian area (shown in red) and launch the Split Objects solver. We click on the big cookie cutter area to use it as the splitting area. The area we've chosen as a splitting area is marked with a small yellow flag. |
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Here is the screen immediately after the split. The big area highlighted in red selection color in the previous step has been split into two areas: a large new area in dotted violet area style and a "rump" area in red selection color representing that part that was not under the splitting area. |
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Here's a closer view with the splitting area removed (we no longer need it.) We can get rid of the red selected area by choosing Edit - Delete to delete it. |
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A
closer view, once again, with the unnecessary area deleted. The
region of Canada forming the northern borders of the Great Lakes has now
been "cut" to the proper shape of the shoreline as guided by
our high resolution "cookie cutter" area.
It does, however, have an ugly area style. The Split Objects solver creates the new objects created by the split in whatever is the active layer when the solver is run. We weren't paying attention a few steps ago when we ran the solver and didn't bother to click on a different layer tab from the tmp layer we used to create the cutting areas. So, when the new, clipped part of Canada was created it was created in the tmp layer and was created with the default, purple dotted transparent area style we had defined for that layer. If we were paying attention, just before running the Split Objects solver we would have clicked on the Countries layer tab to make it the active layer and the new Canadian area would have been created in the Countries layer using our desired formatting for countries. |
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No problem! We click on the new Canadian area and then click on Move to Existing Layer and send it to the Countries layer. We click on the Countries layer tab and choose Apply Default Formatting and all is made perfect. |
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Here is a zoomed out view showing our final product. North America looks better with the Great Lakes, doesn't it? |
