Hi, I have a DTM I want to resample. The original data was in lat/lon SRS which I re-projected to UTM and imported to GRASS GIS.
GRASS 6.4.3 (pampanga_wshed):~ > r.info ifsar_dtm +----------------------------------------------------------------------------+ | Layer: ifsar_dtm Date: Mon Dec 22 10:07:06 2014 | | Mapset: PERMANENT Login of Creator: maning | | Location: pampanga_wshed | | DataBase: /Users/maning/GRASSDATA/ | | Title: ( ifsar_dtm ) | | Timestamp: none | |----------------------------------------------------------------------------| | | | Type of Map: raster Number of Categories: 255 | | Data Type: FCELL | | Rows: 44440 | | Columns: 53950 | | Total Cells: 2397538000 | | Projection: UTM (zone 51) | | N: 1842577.192205 S: 1620332.25097015 Res: 5.00101128 | | E: 420942.75364933 W: 151243.07137293 Res: 4.99906733 | | Range of data: min = -10000 max = 3.402823e+38 | | | | Data Description: | | generated by r.in.gdal | | | | Comments: | | r.in.gdal -e input="ifsar_dtm_utmz51n.vrt" output="ifsar_dtm" | | | +----------------------------------------------------------------------------+ Because of the origin SRS, the pixel size is not the same for ew_res and nw_res. I tried running several resampling techniques to match the pixel size equal to 5. First, I tried r.resamp.interp. g.region rast=ifsar_dtm_subset -pm projection: 1 (UTM) zone: 51 datum: wgs84 ellipsoid: wgs84 north: 1683792 south: 1645429 west: 220827 east: 268500 nsres: 5.00104289 ewres: 4.99926594 rows: 7671 cols: 9536 cells: 73150656 g.region res=5 -ap projection: 1 (UTM) zone: 51 datum: wgs84 ellipsoid: wgs84 north: 1683795 south: 1645425 west: 220825 east: 268500 nsres: 5 ewres: 5 rows: 7674 cols: 9535 cells: 73171590 r.resamp.interp input=ifsar_dtm_subset output=ifsar_dtm_subset_interp_bic method=bicubic --overwrite r.info ifsar_dtm_subset_interp_bic +----------------------------------------------------------------------------+ | Layer: ifsar_dtm_subset_interp_bic Date: Tue Dec 23 13:17:51 2014 | | Mapset: test1 Login of Creator: maning | | Location: pampanga_wshed | | DataBase: /Users/maning/GRASSDATA/ | | Title: Resample by bicubic interpolation ( ifsar_dtm_subset_interp_bic | | Timestamp: none | |----------------------------------------------------------------------------| | | | Type of Map: raster Number of Categories: 255 | | Data Type: DCELL | | Rows: 7674 | | Columns: 9535 | | Total Cells: 73171590 | | Projection: UTM (zone 51) | | N: 1683795 S: 1645425 Res: 5 | | E: 268500 W: 220825 Res: 5 | | Range of data: min = -2.72093853362067 max = 1157.05376343899 | | | | Data Source: | | ifsar_dtm_subset | | Source map NS res: 5.00104289 EW res: 4.99926594 | | | | Data Description: | | generated by r.resamp.interp | | | | Comments: | | r.resamp.interp input="ifsar_dtm_subset" output="ifsar_dtm_subset_in\ | | terp_bic" method="bicubic" | | | +----------------------------------------------------------------------------+ The output resolution matches. Then, I tried r.resamp.rst. g.region rast=ifsar_dtm_subset -pm projection: 1 (UTM) zone: 51 datum: wgs84 ellipsoid: wgs84 north: 1683792 south: 1645429 west: 220827 east: 268500 nsres: 5.00104289 ewres: 4.99926594 rows: 7671 cols: 9536 cells: 73150656 r.resamp.rst input=ifsar_dtm_subset elev=ifsar_dtm_subset_rrst ew_res=5 ns_res=5 --overwrite r.info ifsar_dtm_subset_rrst +----------------------------------------------------------------------------+ | Layer: ifsar_dtm_subset_rrst Date: Tue Dec 23 14:13:49 2014 | | Mapset: test1 Login of Creator: maning | | Location: pampanga_wshed | | DataBase: /Users/maning/GRASSDATA/ | | Title: ( ifsar_dtm_subset_rrst ) | | Timestamp: none | |----------------------------------------------------------------------------| | | | Type of Map: raster Number of Categories: 255 | | Data Type: FCELL | | Rows: 7673 | | Columns: 9535 | | Total Cells: 73162055 | | Projection: UTM (zone 51) | | N: 1683792 S: 1645429 Res: 4.99973935 | | E: 268500 W: 220827 Res: 4.99979025 | | Range of data: min = -2.759012 max = 1157.082 | | | | Data Source: | | raster map ifsar_dtm_subset | | | | | | Data Description: | | generated by r.resamp.rst | | | | Comments: | | tension=617.194349 | | dnorm=64.809407, zmult=1.000000 | | KMAX=50, KMIN=35, errtotal=0.003577 | | zmin_data=-2.600000, zmax_data=1157.017822 | | zmin_int=-2.759012, zmax_int=1157.081551 | | | +----------------------------------------------------------------------------+ Really close but still doesn't match. To visualize the output I created aspect layers for each respection resampling method, but both layer still show checkerboard effects. https://drive.google.com/file/d/0B-2WZQ1DwK_xbUpBTFJzcFdXV2M/view?usp=sharing Any ideas on what I missed? BTW, off topic, is there a way to limit the precision to say 3 decimal places? Centimeter vertical unit should be more than enough for my intended use. -- cheers, maning ------------------------------------------------------ "Freedom is still the most radical idea of all" -N.Branden blog: http://epsg4253.wordpress.com/ ------------------------------------------------------ _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user