title: How to project and resample a grid to match another grid with GDAL python?
body: <p>Clarification:  I somehow left out the key aspect: not using os.system or subprocess - just the python API.</p>
  
  <p>I'm trying to convert a section of a NOAA GTX offset grid for vertical datum transformations and not totally following how to do this in GDAL with python.  I'd like to take a grid (in this case a Bathymetry Attributed Grid, but it could be a geotif) and use it as the template that I'd like to do to.  If I can do this right, I have a feeling that it will greatly help people make use of this type of data.</p>
  
  <p>Here is what I have that is definitely not working.  When I run gdalinfo on the resulting destination dataset (dst_ds), it does not match the source grid BAG.</p>
  
  <pre><code>from osgeo import gdal, osr
  
  bag = gdal.Open(bag_filename)
  gtx = gdal.Open(gtx_filename)
  
  bag_srs = osr.SpatialReference()
  bag_srs.ImportFromWkt(bag.GetProjection())
  
  vrt = gdal.AutoCreateWarpedVRT(gtx, None, bag_srs.ExportToWkt(), gdal.GRA_Bilinear,  0.125)
  
  dst_ds = gdal.GetDriverByName('GTiff').Create(out_filename, bag.RasterXSize, bag.RasterYSize,
                                              1, gdalconst.GDT_Float32)
  dst_ds.SetProjection(bag_srs.ExportToWkt())
  dst_ds.SetGeoTransform(vrt.GetGeoTransform())
  
  def warp_progress(pct, message, user_data):
    return 1
  
  gdal.ReprojectImage(gtx, dst_ds, None, None, gdal.GRA_NearestNeighbour, 0, 0.125, warp_progress, None)
  </code></pre>
  
  <p>Example files (but any two grids where they overlap, but are in different projections would do):</p>
  
  <ul>
  <li><a href="http://surveys.ngdc.noaa.gov/mgg/NOS/coast/F00001-F02000/F00574/BAG/" rel="noreferrer">http://surveys.ngdc.noaa.gov/mgg/NOS/coast/F00001-F02000/F00574/BAG/</a>
   F00574_MB_2m_MLLW_2of3.bag</li>
  <li><a href="http://vdatum.noaa.gov/download/data/VDatum_National.zip" rel="noreferrer">http://vdatum.noaa.gov/download/data/VDatum_National.zip</a>
   MENHMAgome01_8301/mllw.gtx</li>
  </ul>
  
  <p>The command line equivalent to what I'm trying to do:</p>
  
  <pre><code>gdalwarp -tr 2 -2 -te 369179 4773093 372861 4775259 -of VRT -t_srs EPSG:2960 \
       MENHMAgome01_8301/mllw.gtx  mllw-2960-crop-resample.vrt
  gdal_translate mllw-2960-crop-resample.{vrt,tif}
  </code></pre>