Stephane Raynaud wrote:
> Hi,
>
> this scalebar is a really good idea!
>
> However, I suggest that all parameters must be optional:
> - The position could be by default somewhere in the lower left corner
> (for example). It may be interesting to find a "best" position using
> the algo of legend.
> - Then length could be estimated from automatically from the map coordinates.
>
>
>
Stephane: While I agree it would be nice to be able to just say 'give
me a scalebar', I don't think having Basemap choose a default location
and size would be very useful. You want the scalebar to be where there
is nothing else drawn on the map, and this will be different in every
case. Plus, you probably want the length to be a nice round number, not
an arbitrary fraction of the map domain.
-Jeff
> On Tue, Mar 4, 2008 at 3:47 PM, Michael Hearne <[EMAIL PROTECTED]> wrote:
>
>> Jeff - I think the way GMT does it would be okay - they have a latitude of
>> true scale, which I usually choose as the center latitude of the map.
>>
>> I was thinking we should allow people to choose the "simple" or "fancy"
>> options. Do you think it will be okay to have the height of the bar and the
>> text offset be relative to the length of it? I suppose if the height
>> becomes a problem, people could use the yoffset keyword...
>>
>> --Mike
>>
>>
>> On Mar 4, 2008, at 6:05 AM, Jeff Whitaker wrote:
>>
>> Michael Hearne wrote:
>> Jeff - That would replicate the "simple" scale-bar from GMT. Below is my
>> not-complete attempt at replicating the "fancy" scale bar. It would need
>> some options for specifying different units (miles, nautical miles, etc.)
>> and perhaps some more attention to spacing of the text from the scale bar
>> and tick marks...
>>
>> --Mike
>>
>> Mike: Very nice! Do you want the scale to show the true distance on the
>> earth (in which case the labels will vary depending on where the label is
>> placed), or the distance in map projection coordinates (in which case the
>> labels are constant)? Or perhaps a lat/lon value could be given to specify
>> where the scale is true?
>>
>> -Jeff
>>
>> from numpy import *
>> from matplotlib.toolkits.basemap import Basemap, pyproj
>> from pylab import *
>> # add drawscale method to Basemap class.
>> class Basemap2(Basemap):
>> def drawscale(self,lon,lat,length,yoffset=None):
>> """draw a fancy map scale from lon-length/2,lat-yoffset to
>> lon-length/2,lat-yoffset, label it with actual distance in km"""
>> length = length*1000 #input length is km
>>
>> #we need 5 sets of x coordinates (in map units)
>> #center of scale
>> xc,yc = self(lon,lat)
>> #left edge of scale
>> lon1,lat1 = self(xc-length/2,yc,inverse=True)
>> x1,y1 = self(lon1,lat1)
>> #quarter scale
>> lon2,lat2 = self(xc-length/4,yc,inverse=True)
>> x2,y2 = self(lon2,lat2)
>> #three quarter scale
>> lon3,lat3 = self(xc+length/4,yc,inverse=True)
>> x3,y3 = self(lon3,lat3)
>> #right edge of scale
>> lon4,lat4 = self(xc+length/2,yc,inverse=True)
>> x4,y4 = self(lon4,lat4)
>> if yoffset is None: yoffset = 0.1*length
>>
>> #plot top line
>> ytop = yc+yoffset/2
>> ybottom = yc-yoffset/2
>> ytick = ybottom - yoffset/2
>> ytext = ytick - yoffset/2
>> m.plot([x1,x4],[ytop,ytop],color='k')
>> #plot bottom line
>> m.plot([x1,x4],[ybottom,ybottom],color='k')
>> #plot left edge
>> m.plot([x1,x1],[ybottom,ytop],color='k')
>> #plot right edge
>> m.plot([x4,x4],[ybottom,ytop],color='k')
>>
>> #make a filled black box from left edge to 1/4 way across
>> fill([x1,x2,x2,x1,x1],[ytop,ytop,ybottom,ybottom,ytop],'k')
>> #make a filled white box from 1/4 way across to 1/2 way across
>> fill([x2,xc,xc,x2,x2],[ytop,ytop,ybottom,ybottom,ytop],'w')
>> #make a filled white box from 1/2 way across to 3/4 way across
>> fill([xc,x3,x3,xc,xc],[ytop,ytop,ybottom,ybottom,ytop],'k')
>> #make a filled white box from 3/4 way across to end
>> fill([x3,x4,x4,x3,x3],[ytop,ytop,ybottom,ybottom,ytop],'w')
>> #plot 3 tick marks at left edge, center, and right edge
>> m.plot([x1,x1],[ytick,ybottom],color='k')
>> m.plot([xc,xc],[ytick,ybottom],color='k')
>> m.plot([x4,x4],[ytick,ybottom],color='k')
>>
>> #label 3 tick marks
>> text(x1,ytext,'%d' % (0),\
>> horizontalalignment='center',\
>> verticalalignment='top',\
>> fontsize=9)
>> text(xc,ytext,'%d' % (round((length/2)/1000)),\
>> horizontalalignment='center',\
>> verticalalignment='top',\
>> fontsize=9)
>> text(x4,ytext,'%d' % (round((length)/1000)),\
>> horizontalalignment='center',\
>> verticalalignment='top',\
>> fontsize=9)
>>
>> #put units on top
>> text(xc,ytop+yoffset/2,'km',\
>> horizontalalignment='center',\
>> verticalalignment='bottom',\
>> fontsize=9)
>>
>> # setup of basemap ('lcc' = lambert conformal conic).
>> # use major and minor sphere radii from WGS84 ellipsoid.
>> m =
>> Basemap2(llcrnrlon=-145.5,llcrnrlat=1.,urcrnrlon=-2.566,urcrnrlat=46.352,\
>> rsphere=(6378137.00,6356752.3142),\
>> resolution='l',area_thresh=1000.,projection='lcc',\
>> lat_1=50.,lon_0=-107.)
>> # draw coastlines and political boundaries.
>> m.drawcoastlines()
>> m.fillcontinents()
>> # draw parallels and meridians.
>> # label on left, right and bottom of map.
>> m.drawparallels(arange(0.,80,20.),labels=[1,1,0,1])
>> m.drawmeridians(arange(10.,360.,30.),labels=[1,1,0,1])
>> # draw a line from x1,y to x2,y and label it with distance in km.
>> length = 3000 #kilometers
>> x1,y1 = 0.25*m.xmax, 0.25*m.ymax
>> lon1,lat1 = m(x1,y1,inverse=True)
>> m.drawscale(lon1,lat1,length)
>> title('a fancy map scale')
>> show()
>>
>>
>>
>>
>> ------------------------------------------------------
>> Michael Hearne
>> [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
>> (303) 273-8620
>> USGS National Earthquake Information Center
>> 1711 Illinois St. Golden CO 80401
>> Senior Software Engineer
>> Synergetics, Inc.
>> ------------------------------------------------------
>>
>>
>>
>>
>>
>> --
>> Jeffrey S. Whitaker Phone : (303)497-6313
>> NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
>> 325 Broadway Boulder, CO, USA 80305-3328
>>
>>
>>
>>
>>
>> ------------------------------------------------------
>> Michael Hearne
>> [EMAIL PROTECTED]
>> (303) 273-8620
>> USGS National Earthquake Information Center
>> 1711 Illinois St. Golden CO 80401
>> Senior Software Engineer
>> Synergetics, Inc.
>> ------------------------------------------------------
>>
>>
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>>
>
>
>
>
--
Jeffrey S. Whitaker Phone : (303)497-6313
NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
325 Broadway Boulder, CO, USA 80305-3328
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