I've used question on the topic as initial help and structured my code after it. I'm warping a raster file using these kwargs

rast = gdal.Open(/vsicurl/raster_url)
wkt = rast.GetProjection()
outbounds = [-180.00, -90.00, 180.00, 90.00]
warp_kwargs = {
                'format': 'vrt',
                'srcSRS': wkt,
                'dstSRS': 'EPSG:4326',
                'outputBounds': outbounds,

gdal.Warp('/vsimem/rast_1.tif', rast, **warp_kwargs)

I then used this previous question to try to upload the file from /vsimem/ directly into an s3 bucket. I changed a couple things, so my code is as follows. (I use fp to mean filepath)

def upload_to_s3(mem_fp, s3_fp, bucket_name):
    f = gdal.VSIFOpenL(mem_fp, 'rb')
    gdal.VSIFSeekL(f, 0, 2)  # seek to end
    size = gdal.VSIFTellL(f)
    gdal.VSIFSeekL(f, 0, 0)  # seek to beginning
    data = gdal.VSIFReadL(1, size, f)
    # Upload the raw data to s3
    s3 = boto3.client('s3', aws_access_key_id=ACCESS_KEY,
    s3.put_object(Key=s3_fp, Bucket=bucket_name, Body=data, ContentLength=size)

In this case size is the size of the raster and data is b'<VRTDataset rasterXSize="1440" rasterYSize="720" subClass="VRTWarpedDataset">. So this process does upload a file to s3, but it's only 3 kb when it should be around 8 mb. And when I try to download the file from s3 and plot it in QGIS, it errors out saying

ERROR 4: : No such file or directory
ERROR 5: GDALWarpOptions.Validate(): hSrcDS is not set.
gdalinfo failed - unable to open 'test.tif'.

I've tried using both s3.put_object() and s3.upload_file() and neither of them work. I've also tried using an s3.Object.put() which didn't work. I've tried putting the raster in /vsimem/temp which also didn't work. Not sure what else to try here.

  • 1
    Have you looked at that small file? Sounds like you uploaded just the VRT which is a text file describing geodata (and possible transformations). Commented Jan 20, 2021 at 20:11
  • 1
    I'm not exactly sure how to look at it? What tools would I use? Also if that is the case, do you know how to upload the actual raster? would I just change the format in the warp kwargs to GTiff?
    – JWB
    Commented Jan 20, 2021 at 20:22
  • Yep, that seemed to be it. Thank you! I did not realize that you could store GTiff in /vsimem/ I thought that was for VRTs only. You can submit as an answer if you want!
    – JWB
    Commented Jan 20, 2021 at 20:25
  • 3
    In warp kwargs change 'format': 'vrt' to 'format': 'gtiff'. I would consider keeping the warp to VRT, then gdal.Translate to a vsimem tif with compression to reduce file size before uploading the tif.
    – user2856
    Commented Jan 20, 2021 at 21:47
  • @user2856 thank you! If you want put it as an answer, I'll accept it.
    – JWB
    Commented Jan 20, 2021 at 21:52

1 Answer 1


the issue here is within warp_kwargs. User2856 and bugmenot123 both pointed this out. Replace 'format':'vrt' with 'format':'GTiff'. The file that was getting uploaded to s3 was a vrt and not a tif. I was under the impression that only vrt files could be handled within the /vsimem/ directory; however, it works with the other gdal supported file formats!

After making that change, the correct raster file is being uploaded to s3.

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