[gdal-dev] Image reprojection with GDALWARP

Wed Feb 1 09:06:22 PST 2023

Hello, thank you very much for answering, I have added the "-r bilinear" option to the gdalwarp command and this solves the distortion problem, but the reprojection is still wrong with the coordinates of the drawing matching those of the image, and the drawing does not fit the image as it does the original image. How do I have to call gdalwarp so that it does the reprojection correctly, that is, in addition to modifying the image that changes the coordinates and the image projection system? Regards

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Elena Ruiz

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De: Even Rouault <even.rouault at spatialys.com>
Enviado el: miércoles, 1 de febrero de 2023 16:58
Para: Elena Ruiz <eruiz at aplitop.com>; gdal-dev at lists.osgeo.org
Asunto: Re: [gdal-dev] Image reprojection with GDALWARP

Try adding -r bilinear or -r bicubic. By default gdalwarp performs nearest resampling which is rarely what you need for high quality results
Le 01/02/2023 à 16:44, Elena Ruiz a écrit :

Hi, I'm trying to reproject images from WGS 84 / Pseudo-Mercator EPSG:3857 to ED50 / UTM zone 30N EPSG:23030, but the resulting image doesn't adapt well to drawing. I will explain it in more detail so that you understand:

I have an image in EPSG:3857, the result of a WMTS service, and a drawing in the same SRS, as you can see in the image the drawing matches the image perfectly.
Image source with drawing: https://aplitop.sharefile.com/d-s4d6dcf6d8ff34023a8b6e95277519c56

I want to convert the previous image to EPSG:23030 and I have used gdalwarp command with different parameters and I get the same result :

1.gdalwarp -s_srs EPSG:3857 -t_srs EPSG:23030 -co "TFW=YES" -overwrite "C:\Users\elena\Downloads\Nueva carpeta\imagen_t.tif" "C:\Users\elena\Downloads\Nueva carpeta\nueva_6.tif"
2.gdalwarp -s_srs EPSG:3857 -t_srs EPSG:23030 -te 335000 4084501.25 335550 4084848.75 -co "TFW=YES" -overwrite "C:\Users\elena\Downloads\Nueva carpeta\imagen_t.tif" "C:\Users\elena\Downloads\Nueva carpeta\nueva_6.tif"

And the resulting image, in addition to noticing that the road is distorted (like a staircase effect), does not match the drawing.
Image destination with drawing: https://aplitop.sharefile.com/d-s98f76513feb34c268764c0492ccb40d3
Zoom of image destination: https://aplitop.sharefile.com/d-sf9a270a9300e4ac796eddeac7131a058

I have also done the test from EPSG:23030 to EPSG:25830 and it does not do well either.
I am using the version of gdal 2.4.4 for x64, this is the link to download the source and destination image: https://aplitop.sharefile.com/d-sdae2552bd2054fdf8cc29ce5b559e278 , I hope someone can help me and tell me if there is something wrong. Regards
________________________________

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Elena Ruiz
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Tel. +34 952 43 97 71
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