Difference between world_file and image_file when inserting .tiff

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Hello!

I move my .tiff files generated with pix4d mapper to Autodesk software “Map3D”. It’s similar to Autocad but engineered to handle maps better.

My problem is that when I try to enter image file to Map3D it asks me whether I want to use “world file” or “image file” for insertion. One could think that the values are same but for my surprise I discovered that they differ slightly (see PICTURE1).

 

PICTURE 1. Img_file and world_file coordinates inserted as checkpoints in pix4d.

Img_file: 24493012.462 , 6815835.440

world_file: 24493012.453 , 6815835.450

Coordinate system ETRS-GK24 (EPSG 3878)

Why is this? I know the difference is really small but it feels bad because we are using GCP points measured with RTK-unit so it’s quite useless if this step has variance.

2

Hi Reijo,

In some cases, if a software don’t read geotif format or if the orhomosaic was edited in external software (e.g. Photoshop), it uses the tfw and it can happen that you will get a shift of 1/2 pixel.

Possible workarounds are:

  • Use the original GeoTIFF produced in Pix4D software.
  • Add the shift in the .tfw file (+1/2 pixel X coordinate, -1/2 pixel Y coordinate).
  • Use software to copy GeoTIFF metadata http://www.avenza.com/download (if you used an external photo editor)

Best,