Skewed coordinates

Suggestions for WiGLE/JiGLE/DiGLE

5 posts • Page 1 of 1

Postby DoC42 » Thu Nov 04, 2004 5:07 am

I'm traveling to Ireland in december and I was curious about network coverage so I imported a gps range search that covers the entire island into MapPoint to plot them on the map. Most of the locations line up with various businesses and housing developments around the 3 major cities but there's a cluster of a little over 692 out of the 1413 that spill out into the ocean and are several miles south of Dublin and from the pattern it looks like the whole set of data is offset significantly to the southeast and should actually be centered on downtown Dublin.

Is there any way to inform the uploader that somehow his data is skewed?

Postby uhtu » Thu Nov 04, 2004 1:38 pm

we tend to get skewed results from three sources:
1. bad software on our end. our stumble log parsers - while extensive - have bugs like any other software
2. not enough observations of a point (so the one-sided observation skews the point location)
3. bad gps data in the original stumble package.

can you send a few of the MACs in that set to wigle-admin[at]wigle.net (or private message here in the forum), and we'll see if we can find out what is up with that set of points.

thanks!

Postby DoC42 » Thu Nov 04, 2004 5:25 pm

There's so many and they are skewed by miles and relative to eachother so I'm thinking it must be a coordinate system translation problem in the end-users's GPS unit or something like that.

Postby DoC42 » Thu Nov 04, 2004 5:53 pm

I found a couple of sites that I knew the location of out of the skewed set. If I adjust the latitude of all of them by the same amount, they seem to line up latitudinally with the streets but if I adjust the longitude on all of them by the same amount they still seem skewed longitudinally (some still in the water) which makes sense if you've got bad conversion from map grid coordinates to lat/long.

It looks like the Temple Bar district is roughly center of the grid so it might be accurate enough for my purposes in that area. Anything further out of city center is off, though.

Postby uhtu » Thu Nov 04, 2004 6:49 pm

thanks for the list. we'll run through it and see if we can see what is up.

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