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Last Post 21 Jul 2008 11:27 AM by  anon
MAP_SET
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anon



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21 Jul 2008 11:27 AM
    Hello, this question is perhqps out of the scope of seadas, but i dont know who else to ask? i have some images created from Oceancolor L2 files, that are not projected but a specific grid is declared with: latmin, latmax,lonmin,lonmax and latitudestep, longitudestep. so to get the number of column and rows, the following formula is applied: nb_col=fix(((lonmax-lonmin)/longitude)+1) nb_row=fix(((latmax-latmin)/latitudestep)+1) My question is how to declare this type of "projection" in the MAP_set procedure to get the IDL land mask.... In fact it is geographical coordinate (lon,lat). thanks for any help.

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    21 Jul 2008 11:27 AM
    A grid by itself is not a projection. The term "projection", as it is used by MAP_SET, refers to how you want to map your lat/lon data to evenly-spaced pixels in a rectangular coordinate system. To accomplish this MAP_SET [usually] expects the programmer at a minimum to 1) select a well-known projection mapping (e.g. MERCATOR) and 2) the limits (in lat/lon) of the map you want to display (MAP_SET's LIMIT keyword). There are then many optional keywords to MAP_SET that let you set in one call, for example, whether you want to display IDL's built-in map drawing data, how you want grid lines to be drawn and labeled, how you might want the view of your geographical limits rotated, etc. And there are some very specialized keywords for mapping experts that manipulate the data further before projection. James Jones
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