The tfw world file is a text file used to georeference the GeoTIFF raster images, like the orthomosaic and the DSM.
The tfw file is a 6-line file:
Line 1: pixel size in the x-direction in map units (GSD).
Line 2: rotation about y-axis.
Line 3: rotation about x-axis.
Line 4: pixel size in the y-direction in map in map units (GSD).
Line 5: x-coordinate of the upper left corner of the image.
Line 6: y-coordinate of the upper left corner of the image.
As pixels are considered as square lines 1 and 4 are the same.
Article feedback (for troubleshooting, post here instead)
Hi, I submit a problem relating to the .tfw file of the facade ortohplane sgenerated on a survey by UAV and georeferenced with total station.
After processing each project separately (13 different facades) and inserting the control points, I generated and optimized the point cloud and finally generated the orthoplanes.
However, the .tfw file does not contain the geolocation information as opening it with Notepad what appears in all the projects is:
This situation is unpleasant as I have exhausted the Mapper license, promising the customer the delivery in recent days as he has to import and georeference the projects in Autocad (via the "georefimg" command as indicated in your Webinar) and he is unable to import correctly the facades.
I kindly ask you for a timely solution as I am unable to purchase a new license just to solve this problem and above all I have to deliver a quality product to the customer.
Thank you and best regards!
The orthoplane is not georeferenced.
"Note: Only one orthomosaic can be generated at a time. The generated orthomosaic is not georeferenced."
Learn more in How to create the orthomosaic of a facade.
The XY plane of the orthoplane corresponds to the XZ plane of the terrain.
Let's say that you open the orthomosaic on GIS software. The orthomosaic will be placed on earth and the XY coordinates will refer to a known coordinate system. If the orthoplane was georeferenced, it would be wrongly placed on top of the orthoplane, because the XY plane of the orthoplane is the XZ plane of the orthomosaic. On the other hand, if we change the axis, the orthoplane will be visualized as a line over the orthomosaic.
Therefore, the orthoplane is exported in an arbitrary coordinate system where the (0,0) is at the bottom left corner.
If there are GCPs/image geolocation/scale constraint in the project, the orthoplane will be scaled as well.
For the line 5 and 6, (upper left corner of the image) are the coordinates the real upper left coordinates of the image or the coordinates of the center of the upper left pixel?
Both lines refer to the corner of the upper left pixel of the image.
If you need it to be referenced in the center of the upper left pixel you can consider adding the shift in the .tfw file (+1/2 pixel X coordinate, -1/2 pixel Y coordinate).