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

[Adrian Popa]

Yup, it worked like a charm!

Thank you for your help. One more question - how cpu intensive is 
reprojection using mapserver? I mean, if I have 300 users requesting the 
page, will I kill the CPU because it needs to reproject a layer, or are 
the calculations straight-forward and add little extra load on the server?
Can I reproject the layer "offline" and load it without projection in 
mapserver? If I can, which tool would I use (proj4?)?

Thanks again,
Adrian

Rahkonen Jukka wrote:
> 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-
>  
> ------------------------------------------------------------------------
> *L�hett�j�:* mapserver-users-bounces at lists.osgeo.org 
> [mailto:mapserver-users-bounces at lists.osgeo.org] *Puolesta *Adrian Popa
> *L�hetetty:* 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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