Hi Everyone, I'm working in GRASS 6.4RC6 on Win XP and am trying to reproject TRMM rainfall data from its native GCS (WGS84) to a local PCS. I'm using the PCS because my other important data, specifically DEMs, are provided in it. TRMM data come in 0.25°x0.25° squares.
My workfow is as follows: 1. Import the TRMM data into a WGS84 location using r.in.xyz. This gives a raster with the following information: +----------------------------------------------------------------------------+ | Layer: 3b42.00021...@permanent Date: Thu Jul 15 14:42:27 2010 | Mapset: PERMANENT Login of Creator: hanlie | Location: world_wgs84 | DataBase: F:\Hanlie\grassdata | Title: Raw x,y,z data binned into a raster grid by cell mean ( 3B42.000 | Timestamp: none |--------------------------------------------------------------------------- | | Type of Map: raster Number of Categories: 255 | Data Type: FCELL | Rows: 6 | Columns: 3 | Total Cells: 18 | Projection: Latitude-Longitude | N: 27:15S S: 28:45S Res: 0:15 | E: 28:45E W: 28E Res: 0:15 | Range of data: min = 0.000000 max = 0.070614 | | Data Source: | F:\Hanlie\UCT\M.Sc\Data\TRMM\2000\02_Februarie\3B42.000215.0.6.nc.lieb. | | | Data Description: | generated by r.in.xyz | | Comments: | r.in.xyz input="F:\Hanlie\UCT\M.Sc\Data\TRMM\2000\02_Februarie\3B42.\ | 000215.0.6.nc.lieb.txt" output="3B42.000215.0" method="mean" type="F\ | CELL" x=2 y=1 z=3 zscale=1.0 percent=100 | +----------------------------------------------------------------------------+ 2. Set the region to this raster file and create a vector map from it using v.in.region. This gives a vector with the following information: +----------------------------------------------------------------------------+ | Layer: lieb_trmm_reg...@permanent | Mapset: PERMANENT | Location: world_wgs84 | Database: F:\Hanlie\grassdata | Title: | Map scale: 1:1 | Map format: native | Name of creator: hanlie | Organization: | Source date: Thu Jul 15 14:55:13 2010 |----------------------------------------------------------------------------| | Type of Map: vector (level: 2) | | Number of points: 0 Number of areas: 1 | Number of lines: 0 Number of islands: 1 | Number of boundaries: 1 Number of faces: 0 | Number of centroids: 1 Number of kernels: 0 | | Map is 3D: No | Number of dblinks: 0 | | Projection: Lat/Lon | N: 27:15S S: 28:45S | E: 28:45E W: 28E | | Digitization threshold: 0 | Comments: | +----------------------------------------------------------------------------+ 3. Change to the PCS location and reproject the TRMM region using v.proj. This gives a vector with the following information: +----------------------------------------------------------------------------+ | Layer: lieb_trmm_reg...@permanent | Mapset: PERMANENT | Location: sa_tm_29deg_E | Database: F:\Hanlie\grassdata | Title: | Map scale: 1:1 | Map format: native | Name of creator: hanlie | Organization: | Source date: Thu Jul 15 14:55:13 2010 |----------------------------------------------------------------------------| | Type of Map: vector (level: 2) | | Number of points: 0 Number of areas: 1 | Number of lines: 0 Number of islands: 1 | Number of boundaries: 1 Number of faces: 0 | Number of centroids: 1 Number of kernels: 0 | | Map is 3D: No | Number of dblinks: 0 | | Projection: Transverse Mercator | N: -3015356.39959204 S: -3181970.90748457 | E: -24418.1519951 W: -99037.39660484 | | Digitization threshold: 0 | Comments: | +----------------------------------------------------------------------------+ 4. Set the region of the PCS to the TRMM region: g.region -p vect=lieb_trmm_reg...@permanent nsres=25 ewres=25 which gives: projection: 99 (Transverse Mercator) zone: 0 datum: ** unknown (default: WGS84) ** ellipsoid: wgs84 north: -3015356.39959204 south: -3181970.90748457 west: -99037.39660484 east: -24418.1519951 nsres: 24.99842579 ewres: 24.9980719 rows: 6665 cols: 2985 cells: 19895025 I use this resolution because I don't really know what else to use. When I reproject the TRMM GRID into the PCS, I get polygons with differing areas, so I can't use the TRMM grid size as resolution: v.report map=lieb_trmm_squa...@permanent option=area units=kilometers Displaying column types/names for database connection of layer 1: cat|LabelX|LabelY|LblOffsetX|LblOffsetY|Label|gRow|gColumn|RowCol|area 1|28|-28.5|-20|-20|28||||679.062503849138 2|28|-28.25|-20|-20|28||||680.623828116383 3|28|-28|-20|-20|28||||682.172234597964 4|28|-27.75|-20|-20|28||||683.70769882544 5|28.25|-28.75|-20|-20|28.25||||677.428350142518 6|28.25|-28.5|-20|-20|28.25||||679.002141385312 7|28.25|-28.25|-20|-20|28.25||||680.563040996854 8|28.25|-28|-20|-20|28.25||||682.111024322052 9|28.25|-27.75|-20|-20|28.25||||683.646066944101 10|28.25|-27.5|-20|-20|28.25||||685.168144684034 11|28.5|-28.5|-20|-20|28.5||||678.961903132767 12|28.5|-28.25|-20|-20|28.5||||680.522519692921 13|28.5|-28|-20|-20|28.5||||682.070220966439 14|28.5|-27.75|-20|-20|28.5||||683.604982570918 15|28.5|-27.5|-20|-20|28.5||||685.126780361735 5. Reproject the TRMM rainfall from the GCS to the PCS, which gives no data in the file. The extents also seem to be wrong: +----------------------------------------------------------------------------+ | Layer: 3b42.00021...@permanent Date: Thu Jul 15 15:01:05 2010 | Mapset: PERMANENT Login of Creator: hanlie | Location: sa_tm_29deg_E | DataBase: F:\Hanlie\grassdata | Title: ( 3B42.000215.0 ) | Timestamp: none |----------------------------------------------------------------------------| | | Type of Map: raster Number of Categories: 255 | Data Type: FCELL | Rows: 5552 | Columns: 1996 | Total Cells: 11081792 | Projection: Transverse Mercator | N: -3029230.52590567 S: -3168021.78589357 Res: 24.99842579 | E: -36667.20722417 W: -86563.35872871 Res: 24.9980719 | Range of data: min = nan max = nan | | Data Description: | generated by r.proj | | Comments: | r.proj input="3B42.000215.0" location="world_wgs84" mapset="PERMANEN\ | T" method="cubic" resolution=25.0 | +----------------------------------------------------------------------------+ Can someone perhaps see where I'm going wrong? I have hundreds of these files to import, so I need to get the workflow right and then automate the task. Thanks Hanlie _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
