[GRASS-user] Something wrong: Reprojection of raster maps in various platforms: projected coordinates are different
Uttam Kumar
uttamsinha09 at gmail.com
Thu Oct 22 17:21:46 PDT 2015
I could not reach the solution till now even after following the steps told
in previous posts. I know I am making a silly mistake.
This is the projection information of the target location:
+proj=laea +lat_0=30 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs
*GRASS 7.1.svn (SanLuis_Reservoir_LAEA):~ >g.proj -p*
-PROJ_INFO-------------------------------------------------
name : Lambert Azimuthal Equal Area
proj : laea
datum : nad83
ellps : grs80
lat_0 : 30
lon_0 : -96
x_0 : 0
y_0 : 0
no_defs : defined
-PROJ_UNITS------------------------------------------------
unit : Meter
units : Meters
meters : 1
*GRASS 7.1.svn (SanLuis_Reservoir_LAEA):~ > g.proj -w*PROJCS["Lambert
Azimuthal Equal Area",
GEOGCS["grs80",
DATUM["North_American_Datum_1983",
SPHEROID["Geodetic_Reference_System_1980",6378137,298.257222101]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]],
PROJECTION["Lambert_Azimuthal_Equal_Area"],
PARAMETER["latitude_of_center",30],
PARAMETER["longitude_of_center",-96],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["Meter",1]]
*GRASS 7.1.svn (SanLuis_Reservoir_LAEA):~ > v.info <http://v.info> -g
Image_boundary_box*
north=823262.924419209
south=652223.643294404
east=-167210.022680164
west=-518209.054236328
top=0.000000
bottom=0.000000
*I should have got this (This is
correct):north:1638674.575south:1481984.575east:1157941.598west:817651.598*
*Any clue, where am I wrong?*
On Tue, Oct 20, 2015 at 4:45 PM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:
> On 20/10/15 19:08, Uttam Kumar wrote:
>
>>
>>
>> I have been trying for a long time. Something wrong is going on. I
>> appreciate if you can correct me.
>>
>>
>> I have all my source images in sinusoidal projection in a location
>> called "Landsat_sinu".
>>
>> My target locatoin is "Landsat_laea" I tried using the default option in
>> GRASS GUI as follows:
>>
>> 1.) *Select coordinate system parameters from a list*
>>
>> 2.) Projection code: *laea*
>>
>> 3.) Datum with associated ellipsoid:
>> Central parallel: *30*
>> Central Meridian: *-96*
>> False easting: *0*
>> False northing: *0*
>>
>> 4.) Datum code: *nad83*
>> 5.) Select from the list of datum transformation: *1 used in whole nad83
>> region*
>>
>> +proj=laea
>> +lat_0=30
>> +lon_0=-96
>> +x_0=0
>> +y_0=0
>> +no_defs
>> +a=6378137
>> +rf=298.257222101
>> +towgs84=0.000,0.000,0.000
>> to_meter=1
>> +datum=nad83
>>
>> Finish.
>>
>> Is everything ok with this for the below (required) target definition?
>>
>> **PROJ.4 : '+proj=laea +lat_0=30 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83
>> +units=m +no_defs '**
>>
>> Looks like at some point I am making a small mistake. I must get this as
>> the projected coordinates.
>>
>> *north=1064601.38274499
>> south=830176.771464028
>> east=-1960125.15283348
>> west=-2265106.68066176*
>>
>
> And what is wrong with these coordinates ? Those are exactly the ones I
> get and they are very close to the ones you got from ENVI:
>
> > > Upper Left (-2265106.681W, 1064601.383N)
> > > Lower Left (-2265106.681W, 830181.383N)
> > > Upper Right (-1960126.681W, 1064601.383N)
> > > Lower Right (-1960126.681W, 830181.383N)
>
> i.e. 4.6m difference for South and 1.5m difference for East. You would
> have to check how the NAD83 conversion is done exactly to see if the
> difference could come from there.
>
> Moritz
>
>
>
>>
>> Any help is appreciated.
>>
>> Uttam.
>>
>>
>> On Wed, Oct 14, 2015 at 4:52 PM, Moritz Lennert
>> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>>
>> wrote:
>>
>> [Please keep conversations on the list]
>>
>> On 14/10/15 23:19, Uttam Kumar wrote:
>>
>> _
>>
>> _
>> _*This information is for the original data (Source):*_
>>
>> *PROJ.4 : '+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181
>> +b=6371007.181 +units=m +no_defs '*
>>
>>
>> Coordinate System is:
>> PROJCS["Sinusoidal",
>> GEOGCS["GCS_Unknown",
>> DATUM["Unknown",
>> SPHEROID["S_Unknown",6371007.181,0.0]],
>> PRIMEM["Greenwich",0.0],
>> UNIT["Degree",0.0174532925199433]],
>> PROJECTION["Sinusoidal"],
>> PARAMETER["False_Easting",0.0],
>> PARAMETER["False_Northing",0.0],
>> PARAMETER["longitude_of_center",0.0],
>> UNIT["Meter",1]]
>> Origin = (-10801805.197699999436736,4130102.079069999977946)
>> Pixel Size = (30.000000000000000,-30.000000000000000)
>>
>> *
>> _This information is for the destination data (Target):_*
>>
>> *PROJ.4 : '+proj=laea +lat_0=30 +lon_0=-96 +x_0=0 +y_0=0
>> +datum=NAD83
>> +units=m +no_defs '*
>>
>>
>> In your first mail you said:
>>
>> Lambert Azimuthal Equal Area, Datum: WGS84
>>
>> but here the datum is NAD83.
>>
>> Using your projection info, I get almost exactly the same results in
>> GRASS as you report from ENVI:
>>
>> On 08/10/15 21:36, Uttam Kumar wrote:> Reprojected in ENVI (Lambert
>> Azimuthal Equal Area, Datum: WGS84)
>> >
>> -------------------------------------------------------------------------
>> > Corner Coordinates:
>> >
>> > Upper Left (-2265106.681W, 1064601.383N)
>> > Lower Left (-2265106.681W, 830181.383N)
>> > Upper Right (-1960126.681W, 1064601.383N)
>> > Lower Right (-1960126.681W, 830181.383N)
>>
>>
>> GRASS 7.0.1 (test_LAEA):~ > v.info <http://v.info> -g
>> Image_Boundary_box
>> north=1064601.38274499
>> south=830176.771464028
>> east=-1960125.15283348
>> west=-2265106.68066176
>>
>>
>> Don't have the time now to explore the exact differences, but either
>> it's a question of definition of the bounding box, or it possibly be
>> a question of which specific NAD83 transformation parameters were
>> used.
>>
>> Moritz
>>
>>
>>
>>
>
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