[OpenMap Users] Issues with accuracy of polygons

From: Pal, Samarth <SAMARTH.PAL_at_ngc.com>
Date: Tue, 15 Feb 2005 12:18:25 -0800


We are having some issues with moving polygons around on the map. Once we have constructed the polygons, and we select them to move the vertices around, the other points that were not selected to move also shift a little bit on the map.

To re-create a scenarios like this, create a polygon with ~10 vertices. Zoom to about a scale of ~25000. If you now select the polygon, and then move vertex one from point A to point B, then all the other points have slightly moved away. Note that this is not the scenario of moving the whole polygon, but rather moving the individual vertex.

We originally thought that this was because the resolution of a float since that approximately gives a resolution of about 0.5 meters ground distance at the equator. The movement we are noticing on the other points is quite greater than this - on the order of at least couple of hundred feet ground distance, but less than 0.1 mile. This is low resolution in the big picture but 200 to 300 ft movement is not that accurate either.

So the question is that is this the best resolution that is supported by OpenMap or is it actually a bug in the drawing tool when it does conversions from x/y space to lat/lon space?

Has anybody had any issues similar to this related to accuracy of the graphics on the map?

Thanks for the help,

Samarth Pal
Surveillance Planning & Battle Management
Northrop Grumman - Mission Systems
(310) 831-0611 ext. 2979

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Received on Tue Feb 15 2005 - 15:20:46 EST

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