[mapserver-users] Changing the "EXTENT" for a layer

[Rahkonen Jukka]

Hi,
 
Mapserver works without any knowledge about projection with one dataset if only the extents suit the data coordinates. That's the case with your ESRI layer. But you have two datasets which obviously are using different projections.  To show them together either (or both) of them needs to be reprojected.  And that is possible only if you know and tell Mapserver the projections for both datasets.
 
What needs to be done is
1) Set at the MAP level the projection that you want Mapserver to use for output as well as map extents using values and units of the output projection.
2) Set at the LAYER level the projections for both of the datasets.
 
To make is as simple as possible for the beginning I suggest to use projection epsg:4326 and a bit wider extents than you have now at MAP level.  Thats because those extents are already working for you, and ESRI dataset most propably is in WGS84 projection.  Thus you should use projection epsg:4326 also for your ESRI layer.
 
Then there will be just the Mapinfo layer left.  Defined by the the ogrinfo line PARAMETER["central_meridian",27] and coordinates it looks like it might be in UTM 35N projection (epsg:32635).  Have a try with that first.
 
-Jukka Rahkonen-
 
________________________________

Lähettäjä: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Adrian Popa
Lähetetty: 25. helmikuuta 2009 9:25
Vastaanottaja: mapserver-users at lists.osgeo.org
Aihe: [mapserver-users] Changing the "EXTENT" for a layer



	Hello all!
	
	I'm trying to display some layers (ESRI Shapefile and MapInfo) in the same map. The ESRI shapefiles work just fine, and I've used them for a long time. The new MapInfo layer however has very different "Extent" values for its coordinates and does not overlap with the original layers (they should overlap, because they cover the same area).
	
	Here is some output from ogrinfo:
	
	1. A layer that displays ok and for which the coordinates are longitude/latitude:
	
	[adrianp at server data]$ ogrinfo Limits.shp -so -al
	Had to open data source read-only.
	INFO: Open of `Limits.shp'
	      using driver `ESRI Shapefile' successful.
	
	Layer name: Limits
	Geometry: Line String
	Feature Count: 8718
	Extent: (20.261522, 43.618437) - (29.704897, 48.264780)
	Layer SRS WKT:
	GEOGCS["GCS_WGS_1984",
	    DATUM["WGS_1984",
	        SPHEROID["WGS_1984",6378137.0,298.257223563]],
	    PRIMEM["Greenwich",0.0],
	    UNIT["Degree",0.0174532925199433]]
	OBJECTID_1: Integer (9.0)
	TIP: Integer (4.0)
	Shape_Leng: Real (19.11)
	
	2. A layer which displays if I set the Extent parameter in the MAP file to the values returned by ogrinfo:
	
	[adrianp at server data]$ ogrinfo coverage.TAB -so -al
	Had to open data source read-only.
	INFO: Open of `coverage.TAB'
	      using driver `MapInfo File' successful.
	
	Layer name: coverage
	Geometry: Unknown (any)
	Feature Count: 1
	Extent: (550.002594, 4830850.004496) - (707800.001127, 5318099.996174)
	Layer SRS WKT:
	PROJCS["unnamed",
	    GEOGCS["unnamed",
	        DATUM["WGS_1984",
	            SPHEROID["WGS 84",6378137,298.257223563],
	            TOWGS84[0,0,0,-0,-0,-0,0]],
	        PRIMEM["Greenwich",0],
	        UNIT["degree",0.0174532925199433]],
	    PROJECTION["Transverse_Mercator"],
	    PARAMETER["latitude_of_origin",0],
	    PARAMETER["central_meridian",27],
	    PARAMETER["scale_factor",0.9996],
	    PARAMETER["false_easting",500000],
	    PARAMETER["false_northing",0],
	    UNIT["Meter",1.0]]
	LEGEND: String (50.0)
	THRESHOLD: Real (0.0)
	COLOR: String (20.0)
	Prediction_name: String (50.0)
	
	
	I don't know how the second layer was generated (perhaps the values in extent are not longitude/latitude values), but I would like to display both layers in the same coordinate system.
	If I consider the second set of values is longitude/latitude, they make no sense (unless the surface of Earth is the same as the surface of Jupiter!).
	
	My question is: can mapserver do the translation of coordinates (by adding/substracting a fixed value), or do I need to do this with another system?
	If the solution is external to mapserver, what's my next step (some manuals please!)?
	
	I haven't worked with projections; could this be the cause?
	
	Any help is appreciated, thanks!
	Adrian
	
	

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