| Re: MAP_SET vs MAP_PROJ_* [message #42496 is a reply to message #41587] |
Tue, 08 February 2005 08:29  |
Gadhavi
Messages: 5
Registered: February 2005
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Junior Member |
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Dear Friends,
I tried to run the program given by Ben that is mapTest. I found
that map_continent and map_grid subroutines are not accepting the
keyword map_structure. I am using IDL 5.6. The subroutine shown by Ben
is very useful for my purpose. Any suggestion to overcome this problem
Thanking you
HG
Ben Tupper wrote:
> Liam Gumley wrote:
>> Ken Mankoff wrote:
>>
>>
>>
>> I'd love to see a simple example of how the MAP_PROJ routines may
be
>> used with direct graphics. The object graphics example in the IDL
>> documentation is beyond me...
>>
>> For example, how do do you define a Lambert Azimuthal Equal Area
>> Projection in direct graphics centered at a given lat/lon with a
>> specified resolution, such as 1000 meters per pixel?
>>
>
> Hi Liam,
>
> I have tried to take up this challenge with limited success. There
is one
> place in the documentation that gives a bit of a hint (see
MAP_CONTINENTS near
> the bottom.) That, with the shapefile demo in the documents, was
just enough
> fpr me to pull together part of the solution. The code below shows
how to
> generate a projected map with the State o' Maine filled. It ain't
pretty, I
> agree, but it's close.
>
> Tried to ...
> center map a specified location (= done)
> use specified projection ( = done)
> use specified resolution ( = not done)
>
> Note that ...
> Map axes are in !MAP.UV_BOX coords not in LonLat. I guess a
function has to
> be written to show the axes in lonlats using MAP_PROJ_FORWARD as they
would be
> shown using MAP_GRID, /BOX_AXES etc. I don't think that would be
too hard
> (fingers crossed.) I think the hard parts are figuring out the
specified
> resolution and a nice window shape for ISOTROPIC projections. I
wonder if
> MAP_SET could be modified to accept a MAP_STRUCTURE input keyword?
>
>
> Here 'tis...
>
> PRO mapTest
>
> ; GCTP Polar stereographic projection
> myMap = MAP_PROJ_INIT(4, $
> LIMIT = [20, -150, 60, -60],$
> CENTER_LONGITUDE = -120, $
> CENTER_LATITUDE=45)
>
> ; Create a plot window using the UV Cartesian range.
> PLOT, myMap.uv_box[[0,2]],myMap.uv_box[[1,3]], $
> /NODATA, /ISOTROPIC, XSTYLE=1, YSTYLE=1
>
> MAP_CONTINENTS, MAP_STRUCTURE=myMap , /USA
> MAP_GRID, MAP_STRUCTURE=myMap
>
>
> ;Open the states Shapefile in the examples directory
> myshape=OBJ_NEW('IDLffShape', FILEPATH('states.shp', $
> SUBDIR=['examples', 'data']))
>
> ;Get the number of entities so we can parse through them
> myshape->IDLffShape::GetProperty, N_ENTITIES=num_ent
>
> ;Parsing through the entities and only plotting the state of
> ;Colorado
> FOR x=1, (num_ent-1) DO BEGIN
> ;Get the Attributes for entity x
> attr = myshape->IDLffShape::GetAttributes(x)
> ;See if 'Colorado' is in ATTRIBUTE_1 of the attributes for
> ;entity x
> IF attr.ATTRIBUTE_1 EQ 'Maine' THEN BEGIN
> ;Get entity
> ent = myshape->IDLffShape::GetEntity(x)
> xy = MAP_PROJ_FORWARD((*ent.vertices)[0,*],
(*ent.vertices)[1,*], $
> map = myMap)
> ;Plot entity
> POLYFILL, xy[0,*], xy[1,*]
> ;Clean-up of pointers
> myshape->IDLffShape::DestroyEntity, ent
> ENDIF
> ENDFOR
>
> ;Close the Shapefile
> OBJ_DESTROY, myshape
>
> End
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