[SPAM] Re: [UMN_MAPSERVER-USERS] National Atlas Projections... driving me crazy!

[Kelly Koehn]

Tyler:

Thanks for the prompt response.  

LCC may be the incorrect projection that I need to use but it seems to be the only projection that I can find that gives me the counties in the correct (porportional sp?) size.  In the end I would really like to use a Mercator projection but alas I couldn't find any examples to figure out how to make it work.

The specific National Atlas data I'm using is here:
http://edcftp.cr.usgs.gov/pub/data/nationalatlas/countyp020.tar.gz

According to the text file that came with the data they give the following information about the data:
    Latitude/Longitude Resolution: 0.000278
    Geographic Coordinates: Decimal Degrees
    Datum: NAD83
    Ellipsoid: GRS1980
    Semi-major axis: 6378137
    Denomiator of Flattening: 298.257222

Like I said, so far I've been able to get it to produce a map in LCC but its only because I've been playing around with the settings to 'make' it work.  There is a sample map available here: http://www.aspiredillusion.com/cgi-bin/mapserv?map=fmfinder.map&mode=map

In the end my goal is to be able to specify a specific latitude/longitude as a center and be able to plot out so many degrees, miles, whatever out to make a complete map for another project (hence why I think the Mercator projection would be best).

If any of this makes any sense at all let me know because I feel like I'm rambling! :)

By the way... another person suggested to use the EPSG codes... unfortunately my installation is not too happy with using those.  It keeps giving me a Proj.4 error basically saying it can't find the file even though they are located in /usr/local/share/proj.  For now I've just substituted in the definition (or is this bad?)


Here is a copy of my map file:

MAP
        NAME USA
        STATUS ON
        IMAGETYPE PNG
        SIZE 400 400
        IMAGECOLOR 255 255 255
        SHAPEPATH "/home/aspiredillusion/cgi-bin/gis"
        SYMBOLSET "symbol.ref"
        FONTSET "font.ref"
        extent 2086624.47 2893493.42 2267537.24 3111554.05
        UNITS METERS

        PROJECTION
                "proj=lcc"
                "ellps=GRS80"
                "datum=NAD83"
        #       "lat_0=38"      # Latitude CENTER
        #       "lat_1=38"      # Set same as lat_0
        #       "lon_0=-90"     # Longitude CENTER
        #       "x_0=-80000"    # Offset for longitude
        #       "y_0=175000"    # Offset for latitude

                "lat_0=24"
                "lat_1=50"
                "lon_0=-99"
        END

        LAYER
                NAME "County"
                DATA "countyp020"
                TYPE LINE
                STATUS DEFAULT
                PROJECTION
                        "proj=latlong"
                        "ellps=GRS80"
                        "datum=NAD83"
                END
                CLASS
                        OUTLINECOLOR 255 0 0
                END
        END

        LAYER
                NAME "State"
                DATA "statesp020"
                TYPE LINE
                STATUS DEFAULT
                PROJECTION
                        "proj=latlong"
                        "ellps=GRS80"
                        "datum=NAD83"
                END
                CLASS
                        COLOR 0 0 0
                END
        END

        LAYER
                NAME "pop_pnt"
                DATA "pop_pnt"
                TYPE POINT
                STATUS DEFAULT
                LABELITEM "NAME"
                PROJECTION
                        "proj=latlong"
                        "ellps=GRS80"
                        "datum=NAD83"
                END
                CLASS
                        STYLE
                                SYMBOL "circle"
                                SIZE 3
                                COLOR 0 0 0
                        END
                        LABEL
                                COLOR 0 0 0
                                FONT "arial"
                                SIZE 10
                                TYPE TRUETYPE
                                POSITION AUTO
                                OUTLINECOLOR 255 255 255
                                BUFFER 8
                        END
                END
        END


        LAYER
                NAME "Notation"
                STATUS DEFAULT
                TRANSFORM FALSE
                TYPE ANNOTATION
                FEATURE
                        POINTS
                                33 390  # Across, Down
                        END
                        TEXT 'FMFinder'
                END
                CLASS
                        LABEL
                                FONT "arial"
                                TYPE TRUETYPE
                                SIZE 10
                                BUFFER 1
                                COLOR 0 128 255
                                FORCE TRUE
                                BACKGROUNDCOLOR 255 255 255
                        END
                END
        END
END


  ----- Original Message ----- 
  From: Tyler Mitchell 
  To: Kelly Koehn 
  Cc: MAPSERVER-USERS at LISTS.UMN.EDU 
  Sent: Monday, July 24, 2006 10:42 PM
  Subject: [SPAM] Re: [UMN_MAPSERVER-USERS] National Atlas Projections... driving me crazy!


  Hi Kelly,
  I'm not familiar with your national atlas specific projections, but do you have more details about the LCC projection you are referring to?  LCC is a general class of projection that will have some more localised parameters depending on, generally speaking, where you are centering your map.  The lat_0/1/2 and lon_0 values might change depending on where you are doing your mapping.  


  Do you already know the more full description of the LCC projection you have in mind?


  Tyler


  On 24-Jul-06, at 6:49 PM, Kelly Koehn wrote:


    I've been working with mapserver for quite some time now and I thought I'd made some strides in the areas of projections but I seem to have went into it all backwards.  I started out with the National Atlas datasets for counties and states.  I've come to the conclusion that the projection they want you to use is 'latlong', ellps is 'GRS80', and datum is 'NAD83'.  The names are 'statesp020' and 'countyp020' I believe.

    This is all fine and dandy except unless you project the map as LCC it seems to be vertically challenged.  For instance, the county that I live in (Sedgwick, in Kansas) is not a rectangle.. its square.  I've found some examples of the lat/long to LCC projection but most seem a bit foggy.

    My real question has to do with the whole 'lat/long to meters' conversion and how to make heads or tails of the 'cs2cs' program that supposedly converts the values.    Is there some magic trick to this program that I'm not finding? 

    I have some other questions about exactly what the lat_0, lat_1, lat_2, lon_0 values should be for the LCC projection but I'll save those for another time.

    Any help would be great! I'm about ready to rip my hair out!

    Kelly




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