[GRASS-dev] [GRASS GIS] #167: g.region: reports wrong center longitude and LL bounding box

[GRASS GIS]

#167: g.region: reports wrong center longitude and LL bounding box
--------------------------+-------------------------------------------------
 Reporter:  hamish        |       Owner:  grass-dev at lists.osgeo.org
     Type:  defect        |      Status:  new                      
 Priority:  major         |   Milestone:  6.4.0                    
Component:  default       |     Version:  svn-develbranch6         
 Keywords:  g.region 180  |  
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 Hi,

 if you set up a region which crosses 180 longitude, g.region -b and -l
 have problems calculating the center coord:

 create a new location using EPSG 3112. (Australia; Lambert CC)
 {{{
 g.region n=1973000 s=-6188000 w=-5175000 e=4846000 res=1000
 d.mon x0; d.grid -g 10
 # looks ok, if you ignore that grid lines E of 180 are missing
 }}}
 ---
 {{{
 g.region -b   # print max LL bounding box (WGS84)
 north longitude:  19:37:06.913074N
 south longitude:  44:19:08.88403S
 west latitude:    69:34:08.058065E
 east latitude:    168:13:13.623433E
 center latitude:  118:53:40.840749E
 center longitude: 12:21:00.985478S
 }}}

 /general/g.region/printwindow.c:
  * lat/lon swapped;  "north longitude" -> "North latitude" etc.

 after fixing that, the max bounding box calc still is wrong.
 furthest east is the bottom right corner (165W) but -b reports the value
 at the top right (168E).  [simple a>b test too simple?]
 That eastern boundary value is used for the center lon calc, so the center
 lon is wrong as well (skewed to the west).


 ---
 {{{
 g.region -l    # print lat/lon  (current ellipsoid)
 north-west corner: long: 97:34:49.670961E lat: 20:13:08.52602N
 north-east corner: long: 168:13:13.623433E lat: 19:37:06.913074N
 south-east corner: long: 165:02:10.589072W lat: 44:19:08.88403S
 south-west corner: long: 69:34:08.058065E lat: 42:56:48.735964S
 center longitude:  42:35:00.190847E
 center latitude:   11:51:25.545225S
 rows:              8161
 cols:              10021
 }}}

 this time it gets the box corners correct but the center longitude is
 wrong. it's looking around the wrong side of the world and the answer is
 apparently 180deg out.

 also note the center lat is different to the -b version, and that with -l
 the NW corner's lat is bigger than the NE lat, but for -b max bounding box
 the more southerly 19:37N is used, not the further out 20:13N.



 Hamish

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Ticket URL: <http://trac.osgeo.org/grass/ticket/167>
GRASS GIS <http://grass.osgeo.org>