Visual fusion 5_radial_query_improvements
by IDV Solutions on Sep 28, 2010
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Our out of the box radial query lets you click a spot, drag out a radius, and summarize the data within. Except, in the past, we've been a little less than precise about how that radius should ...
Our out of the box radial query lets you click a spot, drag out a radius, and summarize the data within. Except, in the past, we've been a little less than precise about how that radius should really look on the map; we drew a nice, perfect, circle. But a perfect circle in Mercator does not necessarily mean a circle in real life!
Here's the lowdown: the basemap projection used by Visual Fusion (and virtually all other web maps) is Mercator. There are lots of great reasons for this, but you can read about those for extra credit. What matters in this case is that Mercator tends to exaggerate the relative size of things as you get away from the equator. This means that a real-life circle of 1,000 miles drawn truthfully on Mercator would start to look a: way bigger, and b: teardrop shaped, the further north or south you draw it (at the equator it's a well behaved little circle).
Visual Fusion 5.0 (October 2010) draws radials as actual geographic distances (perfect circles in the real world, bloated teardrops in Mercator). Because we like truth and precision.
When dragging out a radius, we label the distance that you have covered. In version 5.0, this label also acts as in input text box, so you can just type in any distance you want. It turns out, dragging a very precise distance can be difficult (or even impossible, if your distance units are smaller than the number of pixels in the radius). Problem no more!
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