[Geoinquiets Barcelona] comparar zones

[Alexandre Nobajas]

Com diu a baix, comparar superfícies amb una projecció de tipus Mercator és agosarat. Però com a divertimento està molt bé!

Shape Distortion

If you draw the outline at a given latitude in the Reference map, and
 then view the outline at a different latitude in the Comparison map, 
the relative orientation of the marker positions will be distorted. This
 distortion occurs for two different reasons.

First, Google Maps uses a
Mercator projection
for its maps. By design, this projection distorts distances at different latitudes. Distances are magnified at higher latitudes.

Second, my calculation of comparison marker positions attempts to 
preserve true distances between markers. These calculations account for 
the fact that units of longitude have different lengths depending on 
latitude. The calculations somewhat reverse Mercator distortions of 
horizontal distances, but not vertical distances.

--- On Wed, 2/23/11, Raf Roset <rafroset at gmail.com> wrote:

From: Raf Roset <rafroset at gmail.com>
Subject: [Geoinquiets Barcelona] comparar zones
To: barcelona at lists.osgeo.org
Date: Wednesday, February 23, 2011, 11:05 AM

Per comparar superfiícies a Google Maps http://mapfrappe.com/index.html?show=2385 (no som res!)

Raf


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