map projection question from a newbie

[Stephen Woodbridge]

Hi James,

You are doing nothing wrong. Mapserver takes the coordinate in the file 
and treats them as X/Y and generates the images based on this. If you 
plot geographic long/lat as X/Y you get an elongated image. xastir must 
be compensating for the fact that it is geographic data and applying a 
hidden projection of some type.

Mapserver does not do this. if you want it projected you have to 
EXPLICITLY tell it to perform a projection.

In the mapfile, you can define the OUTPUT projection in the MAP object 
and the projection that the data is in in the LAYER object, or you can 
leave all the PROJECT ... END blocks out if they are all the same and it 
will just plot the data as X/Y.

-Steve W.

James Washer wrote:
> I'm a newbie to mapping in general, so please have mercy if I'm asking stupid questions.
> 
> I have a shapefile that was given to me in Nevada State Plane, and I used shpproj to reproject as follows:
>  shpproj stateplane_shapefile geographic_shapefile -i="init=nad83:2703 units=us-ft" -o=geographic
> 
> The map looks perfect when I view it in xastir (ham radio APRS mapping program) but looks about 30% too wide when viewed with mapserver.
> 
> Here's the map file... Any ideas what I'm doing wrong?
> 
> thanks for reading this far.
> 
>  - jim
> 
> MAP
> 	IMAGETYPE      PNG
> 	#EXTENT	-119.961409 38.535114 -119.310436 39.113979
> 	EXTENT	-120.0 38.535114 -119.25 39.113979
> 
> 	SIZE           600 600
> 	SHAPEPATH      "/usr/local/share/xastir/maps/Douglas/Parcels"
> 	#SHAPEPATH      "/var/www/html/gis/Douglas/Parcels"
> 	IMAGECOLOR     200 200 200
> 
> 	WEB
> 		TEMPLATE doug2-1.html
> 		IMAGEPATH "/var/www/html/gis/tmp/"
> 		IMAGEURL "/gis/tmp/"
> 	END
> 	
> 	LEGEND
> 		STATUS EMBED
> 		POSITION LR
> 		#TRANSPARENT TRUE
> 	END
> 
> 	UNITS DD
> 
> 
>        PROJECTION
>                 "proj=latlong"
>                 "ellps=WGS84"
>        END
> 
> 
> 
> 	SCALEBAR
> 		STATUS EMBED
> 		UNITS MILES
> 		INTERVALS 3
> 		OUTLINECOLOR 0 0 0
> 	END
> 
> 	LAYER # States polygon layer begins here
> 		NAME         Parcels
> 		DATA         dc_pcls1
> 		STATUS       DEFAULT
> 		TYPE         POLYGON
> 		LABELITEM	TAG
> 		#CLASS
> 			#NAME	"TAG"
> 			#EXPRESSION 
> 
> 		CLASS
> 			NAME       "Douglas County Parcels"
> 			STYLE
> 				COLOR        232 232 232
> 				OUTLINECOLOR 32 32 32
> 			END
> 			LABEL
> 				SIZE LARGE
> 				MINFEATURESIZE 200
> 			END
> 		END
> 	END
> 
> END
>