Support Website Contact Support Blog

How to interpret TFW and PRJ files for georeferentiation


I have an ortho map created by pix4d, and I need to use its georeferentiation. However, I cannot correctly interpret the information of the world’s files:



I know this:

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.

What are the units of x-coordinate and y-coordinate?

I also have the .prj file which I cannot interpret:

PROJCS[“WGS 84 / UTM zone 29N”,GEOGCS[“WGS 84”,DATUM[“WGS_1984”,SPHEROID[“WGS 84”,6378137,298.257223563,AUTHORITY[“EPSG”,“7030”]],AUTHORITY[“EPSG”,“6326”]],PRIMEM[“Greenwich”,0,AUTHORITY[“EPSG”,“8901”]],UNIT[“degree”,0.0174532925199433,AUTHORITY[“EPSG”,“9122”]],AUTHORITY[“EPSG”,“4326”]],PROJECTION[“Transverse_Mercator”],PARAMETER[“latitude_of_origin”,0],PARAMETER[“central_meridian”,-9],PARAMETER[“scale_factor”,0.9996],PARAMETER[“false_easting”,500000],PARAMETER[“false_northing”,0],UNIT[“metre”,1,AUTHORITY[“EPSG”,“9001”]],AXIS[“Easting”,EAST],AXIS[“Northing”,NORTH],AUTHORITY[“EPSG”,“32629”]]

How can I georefentiate an image from this?

Hi Luis,

Have in mind that our outputs are already georeferenced so you do not need to take any further actions to do that. May I ask if you are trying to georeference the orthomosaic?

Regarding the TFW file and in my understanding the coordinate system you used is WGS 84 / UTM zone 29N, this means that the unit of x-coordinate and y-coordinate is the meter (m) and also the pixel value you selected it when you selected the resolution of the DSM and the orthomosaic. In the image below the resolution is set to 6.92 cm which means that the pixel size in x and y direction in map is 0.06920000000 m on my occasion.

Regarding the prj file you can have a look at link 1 and link 2 for interpreting it.