Re: [Matplotlib-users] Basemap questions

[Michael H. <mh...@us...>]

Jeff -

My data set is actually dynamically generated by a program called  
ShakeMap.  It's a 2D grid, with an extent usually about 600  
kilometers on a side, centered wherever the earthquake happened to  
be.  The ShakeMap program does not know or care that some of the data  
may be under water, but for display purposed, I do!  The grid is also  
in a geographic projection (latitude/longitude coordinates assumed to  
be cartesian).

So in this test instance (on a data set near Taiwan), my map width is  
about 5.91 degrees longitude, and my height is about 5.5 degrees  
latitude.

If I set xoffset=-0.01*5.91, I get -0.05.  This is not noticeably  
different than the default.

Is the problem that my dataset is not projected?

--Mike
On Nov 2, 2007, at 1:33 PM, Jeff Whitaker wrote:

> Michael Hearne wrote:
>> Jeff - I looked at that example file, and I think there's a big  
>> difference - your etopo base data set is global, and you can plot  
>> over the data in the oceans by setting the mask on all pixels less  
>> than zero.
>>
>> My dataset (a map of earthquake shaking) is not global, and  
>> actually has NO missing data.   I think I need a way to "clip" the  
>> data by the land mask - that is, find all of the pixels that are  
>> NOT on land, and then mask them off.
> Mike:
>
> If it's not global, is it just defined for land points?  If so, it  
> can't be a 2-D grid, so you won't be able to plot it with imshow  
> anyway.  Can you explain the structure of the data?
>>
>> Is there an easy way to do this with matplotlib/basemap tools?
> Not really.  You'll have to define a sea mask for your grid and use  
> that the create a masked array.  There is a land-sea mask dataset  
> included in basemap, but it may not match the resolution of your grid.
>
>>
>> Regarding my other issue - I used my script to test x/y offset  
>> values: [0.05,0.1,0.5,1.0,10] and couldn't see any difference.   
>> I'd be more than happy to provide test output, or debugging  
>> information...
>>
>> Just to be clear - these offsets are supposed to move the meridian  
>> and/or parallel labels around with respect to the map edge?  My  
>> actual goal is to get the labels inside the edge of the map (I  
>> tried negative numbers to accomplish this, to no effect.)
> You  need to define an offset as a fraction of the map width - the  
> numbers you are giving are too small to notice any difference.  As  
> I said before, try something like -0.01*(m.max-m.min).
>>
>> On a positive note, I _can_ make solid lines!
>
> Good!
>
> -Jeff
>
> -- 
> Jeffrey S. Whitaker         Phone  : (303)497-6313
> Meteorologist               FAX    : (303)497-6449
> NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no...
> 325 Broadway                Office : Skaggs Research Cntr 1D-124
> Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg




------------------------------------------------------
Michael Hearne
mh...@us...
(303) 273-8620
USGS National Earthquake Information Center
1711 Illinois St. Golden CO 80401
Senior Software Engineer
Synergetics, Inc.
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