Warping images with unknown projection

Question

I have tried to used gdalwarp to project set of images(from hdf4 files to tif) before merging them using gdal_merge. But then the merge output has spaces/blanks. They're not merge properly, and I don't know why'd it happened like that. So I thought of merging first before projecting, when I tried to project the merge hdf files an error like this always appears:

ERROR 1: Unable to compute a transformation between pixel/line and georeferenced coordinates for merge.tif. There is no affine transformation and no GCPs.

Command line code: gdalwarp -te 109.975 3.475 135.025 25.025 merge.tif new.tif

Here is the gdalinfo:

Driver: HDF4Image/HDF4 Dataset
Files: A2014348055000.L2_LAC.SeAHABS.hdf
Size is 1160, 1990
Coordinate System is `'
Metadata:
  bad_value_scaled=-32767
  bad_value_unscaled=-32767
  Calibration Data=A2014348055000.L1A_LAC.eAHAB.hdf, MYD02_Reflective_LUTs.V6.1.17.24_OC.hdf, MYD02_Emissive_LUTs.V6.1.1
7.24_OC.hdf, MYD02_QA_LUTs.V6.1.17.24_OC.hdf
  cdm_data_type=swath
  Conventions=CF-1.6
  creator email=data@oceancolor.gsfc.nasa.gov
  creator name=NASA/GSFC/OBPG
  creator url=http://oceandata.sci.gsfc.nasa.gov
  date_created=20141214T092342Z
  Day or Night=Day
  Earth-Sun Distance Correction=1.03201282024384
  Easternmost Longitude=125.8173065
  End Center Latitude=25.38609505
  End Center Longitude=112.290802
  End Day=348
  End Millisec=21301577
  End Node=Ascending
  End Time=2014348055501577
  End Year=2014
  Flag Percentages=0.0001732801902, 22.30172539, 0.001126321382, 15.12727451, 80.96486664, 3.97266531, 5.644948959, 0, 1
5.79899502, 81.37419891, 0.1860162914, 0.8686535954, 0, 0, 0.2047305405, 0.01342921611, 0, 0, 0, 0.08087852597, 43.33668
518, 0.0002599202853, 0.1081701592, 0, 0, 0, 0, 68.54501343, 22.30384445, 0.1022786349, 94.91210175, 0
  geospatial_lat_max=26.48568916
  geospatial_lat_min=6.694877148
  geospatial_lat_units=degrees_north
  geospatial_lon_max=125.8173065
  geospatial_lon_min=105.5096741
  geospatial_lon_units=degrees_east
  Input Files=A2014348055000.L1B_LAC.SeAHABS.hdf,S201434718_NCEP.MET,S201434718_NCEP.MET,S201434718_NCEP.MET,N201434500_
O3_AURAOMI_24h.hdf,N201434500_O3_AURAOMI_24h.hdf,N201434500_O3_AURAOMI_24h.hdf,,xcal_modisa_axc26f,polcor_modisa_2010b,m
odisa_ocr_vc_nn,,landmask.dat,watermask.dat,digital_elevation_map.hdf,ETOPO1_ocssw.nc,,N201434600_SEAICE_NSIDC_24h.hdf,s
st_climatology.hdf,sss_climatology_woa2009.hdf,no2_climatology.hdf,alpha510_climatology.hdf,taua865_climatology.hdf,A201
4348055000.GEO,owmc_lut.hdf,


Geolocation:
  LINE_OFFSET=0
  LINE_STEP=1
  PIXEL_OFFSET=0
  PIXEL_STEP=1
  SRS=GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0
,0,0,0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHOR
ITY["EPSG","9108"]],AUTHORITY["EPSG","4326"]]

Answer 1

As a reference, I took the file linked here: http://oceancolor.gsfc.nasa.gov/forum/oceancolor/topic_show.pl?tid=5426

gdalinfo on the subdataset 37 returns:

geospatial_lat_max=24.78230858
geospatial_lat_min=5.343300343
geospatial_lon_max=139.3295746
geospatial_lon_min=126.3987579
...
Lower Left Latitude=24.78230858
Lower Left Longitude=134.9941864
Lower Right Latitude=23.15408325
Lower Right Longitude=126.3987579
...
Upper Left Latitude=6.639705181
Upper Left Longitude=139.3295746
Upper Right Latitude=5.343300343
Upper Right Longitude=131.3719025
Corner Coordinates:
Upper Left  (    0.0,    0.0)
Lower Left  (    0.0, 2040.0)
Upper Right (  423.0,    0.0)
Lower Right (  423.0, 2040.0)

These form a rectangle rotated to the east and north axis.

You have to use gdalwarp with the -geoloc option and -te from the geospatial_... tags:

gdalwarp -geoloc -of GTIFF -t_srs EPSG:4326 -te 126.3987579 5.343300343 139.3295746 24.78230858  HDF4_SDS:UNKNOWN:"A2014037040500.L2_LAC.SeAHABS.hdf":37 sds37.tif

which uses the geolocation information that is stored in the subdatasets 11 and 12.

Another way is to add gcp for all four points with gdal_translate:

gdal_translate -of VRT -a_srs EPSG:4326 -gcp 0 0 139.3295746 6.639705181 -gcp 423 0 131.3719025 5.343300343 -gcp 0 2040 134.9941864 24.78230858 -gcp 423 2040 126.3987579 23.15408325 HDF4_SDS:UNKNOWN:"A2014037040500.L2_LAC.SeAHABS.hdf":37 neu.vrt
gdalwarp -of GTIFF -tps neu.vrt 2014.tif

which puts the data in the right position: