[OSM-talk] Missing tiles?

[Mark Williams]

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Lukasz Szybalski wrote:
>>  openstreetmap.org and click the "export" tab; then "manually select
>> an area...". Draw the area you want, and the four text boxes will show
>> min and max lat/lon.
>>
>> This is perfect,,,,,except which number is what?
>>
>>        56
>> -132      -67
>>       25.5
> 
> Also could you add in generate_tiles.py what is what:
> 
> #bbox( left, bottom, right ,top)
> #bbox( minlong, minlat maxlong ,maxlat)   correct?
> Without being an expert I don't know what is min long max long, and
> min lat vs max lat.
> 
> Thanks,
> Lucas
> 
These numbers are latitude (up & down on the globe, if you will) &
longitude (distance horizontally around the globe, starting at
Greenwich, England = 0).
The latitude goes from -90 at the south pole to 0 at the equator to +90
at the north pole, and the longitude -180 to +180.

A box is most easily specified as 4 numbers, with the topmost latitude
drawn at the top, the most eastern longitude to the left, etc.. Think of
it in the context of a globe, or map, with those numbers written in the
appropriate place on it.

minlat is the minimum (ie lowest, southernmost) latitude (so the lowest
in the group of 4, ie 25.5 in your example), maxlat the highest (56),
and longitude works just the same.

So to convert the above to a bbox gives you bbox(-132, 25.5, -67, 56)

Does that clear it up a bit?

Mark
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