gistfile1.rb

ruby-1.8.7-p249 > Geokit::Bounds.from_point_and_radius([53.91848,-122.776584], 4993)
 => #<Geokit::Bounds:0x1050e7580 @ne=#<Geokit::LatLng:0x1050e8e08 @lat=53.897792470202, @lng=-43.4942376451051>, @sw=#<Geokit::LatLng:0x1050e8e58 @lat=-18.265247529798, @lng=-202.058930354895>> 
ruby-1.8.7-p249 > Geokit::Bounds.from_point_and_radius([53.91848,-122.776584], 4997)
 => #<Geokit::Bounds:0x1050dee08 @ne=#<Geokit::LatLng:0x1050e0690 @lat=53.8399645290606, @lng=-43.4579700787395>, @sw=#<Geokit::LatLng:0x1050e06e0 @lat=-18.3230754709394, @lng=-202.09519792126>>

Shouldn't @lat=53.8399645290606 in line 4 be a larger value than @lat=53.897792470202 found on line 2?

what bothers me much is the @lng=-202.xxx Is it even valid?

What formula and distance unit do you use ?

Here is the relavent section of the config:

Geokit::default_units = :kilometers
Geokit::default_formula = :sphere

I didn't write this code, but when looking at the Geokit code, isn't kilometers supposed to be expressed as :kms or can it use :kilometers as specified in the config?

I don't know Geokit but.

IIUC, you are asking for the bounding rectangle around a circle, there are two points there, It looks like the first is the bottom left corner, and for a larger radius it should be further west, and south, and it seems to be, The second is further east and north.

@rubyredrick Are you saying that lat/long pair associated with @ne is actually the bottom left corner (i.e. the southwest corner)?

@rubyredrick I think that the first pair, ie. @ne=#<Geokit::LatLng:0x1050e0690 @lat=53.8399645290606, @lng=-43.4579700787395> is the northeast corner. If this is true then a larger bounding box should result in lat moving farther from 0 and lng moving closer to 0, no?

@aeden I can confirm that the @ne point is the North/East corner and @sw is the South/West corner.

GoogleMaps uses the same representation for bounds.

@jlecour Thanks for confirming it. Do you agree then that the lat in the ne value should be moving away from 0 given the increase in the radius (i.e the increase in the distance)?

Ok I didn't notice the iv names.

There's another thing wonky here, going 4993 km north should change the longitude by about 45 degrees (approx 111 km/degree) instead in both cases it's only changing about a tenth of 1 degree.

I guess that with such big distances, it's crossing the usual limits of -180/+180 for the longitude and -90/+90° for the longitude.

I think that Geokit does good with crossing the longitude limits, but I don't know about latitude.

Yep, I'm sure that's the problem.

As I pointed out the diameter either of those circles should be around 90 degrees in latitude, at 40 degrees north each degree of latitude is only 85 km, and at 54 north even less, so the diameter in longitude is greater than 120 degrees

Generalized spherical geometry for navigation has a singularity at each pole. Things get really wonky near the arctic circles, too. 54deg North is pretty "up there" I'd try shrinking your radius to 10km and then increase it again until you see things break.

Also, it depends on which algorithm GeoKit is using. There's a simplified formula which doesn't account for sign changes; it works fine for small ranges and is much faster; it just won't cross poles or the international dateline. In addition, like I said, these formulae start to break down as you get near the poles -- somewhere sine(theta) is approaching 0.