global mapping issues with orthographic projection

[Sean Gillies]

On Apr 27, 2005, at 2:30 PM, Ken Tanaka wrote:

> As an update/resolution to this problem, we now have a corrected map
> file that generates the image we want.
> The resulting imag is online:
> http://gdsg.ngdc.noaa.gov/starburst/OrthoOutlines.html
> The image was positioned to correspond to the GOES-EAST geostationary
> satellite data we will be processing.
>
> Thanks again for the help from this email list.
>
> ===========
> MAP
>     IMAGETYPE GIF
>     EXTENT -6400000 -6400000 6400000 6400000
>     SHAPEPATH "/df_env/MMS/"
>
>     PROJECTION
>         "+proj=ortho"
>         "+lat_0=0.0"
>         "+lon_0=-75.0"
>     END
>
> # Start of LAYER DEFINITIONS
> ---------------------------------------------
>
>     LAYER # States polygon layer begins here
>         NAME states
>         DATA "statesp020"
>         STATUS off
>         TYPE polygon
>
>          CLASS
>             COLOR 0 0 0
>                 OUTLINECOLOR 255 0 0
>          END
>
>         PROJECTION
>            "init=epsg:4326"
>         END
>     END # States polygon layer ends here
>
>     LAYER # Countries polygon layer begins here
>         NAME countries
>         DATA "countries"
>         STATUS off
>         TYPE polygon
>
>          CLASS
>             COLOR 0 0 0
>                 OUTLINECOLOR 255 0 0
>          END
>
>         PROJECTION
>            "init=epsg:4326"
>         END
>     END # Countries polygon layer ends here
>
> # End of LAYER DEFINITIONS
> ---------------------------------------------
>
> END
> ===========
>
> Ken Tanaka wrote:
>
>> ...
>
>> At the moment we are having some troubles with a "starburst" of stray
>> feature lines that can be seen in this URL:
>>
>> http://gdsg.ngdc.noaa.gov/starburst/
>>
>>
>>
>>>> Our current approach is to generate the lines with MMS, and then
>>>> use a
>>>> separate step to merge the data (satellite image) with the outlines
>>>> image,
>>>> and produce the composite image seen in the above URL.
>>>>
>>>>
>>> Frank Warmerdam wrote:
>>
> ...
>
>>> Is there a reason you don't have MapServer taking care of the image
>>> data
>>> as well?
>>>
>>>
>> I think having MapServer handle the image data would be a good
>> approach
>> as well. We are currently trying MapServer out by replacing older
>> software in an existing system. I'll need to find out why the merging
>> is
>> done separately, there may be a performance issue there.
>>
>>
> Primarily we are taking this approach as an efficiency step. The data
> images will remain in the same perspective, so we can use MapServer for
> the  overlay one time for this perspective. This is potentially a large
> number of images, especially if we are required to re-process the
> existing archive.
>
> -Ken
>

Ken,

Instead of declaring a black fill for your country and states polygon
and then making black transparent, you can simply omit the fill color.
The result is will be a stroked polygon with no fill at all, and will
overlay your image nicely.  Should be faster, too.

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies