Update tutorials.rst

source/tutorials.rst

@@ -102,15 +102,17 @@ Ground control points are useful for correcting distortions in the data and refe
 
 	The format of the GCP file is simple.
 
-	 * The header line is a description of a UTM coordinate system, which must be written as a proj4 string. http://spatialreference.org/ is a good resource for finding that information. Please note that currently angular coordinates (like lat/lon) DO NOT work.
-	 * Subsequent lines are the X, Y & Z coordinates, your associated pixels and the image filename:
+	 * The first line should contain the name of the projection used for the geo coordinates.
+	 * Subsequent lines are the X, Y & Z coordinates, your associated pixels and the image filename.
 
 	GCP file format::
 
-	    <proj4 string>
+	    <projection string>
 	    <geo_x> <geo_y> <geo_z> <im_x> <im_y> <image_name>
 	    ...
 
+WGS84, UTM, and proj4 geospatial coordinates are supported. For more information about the file format read the `Ground Control Points Format Specification <https://github.com/mapillary/OpenSfM/blob/master/doc/source/gcp.rst/>`_.
+
 	e.g. for the Langley dataset::
 
 	    +proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
@@ -146,7 +148,7 @@ Create a GCP list that only includes gcp name (this is the label that will be se
 
 Then one can load this GCP list into the interface, load the images, and place each of the GCPs in the image.
 
-`Help edit these docs! <https://github.com/OpenDroneMap/docs/blob/publish/source/using.rst>`_
+`Help edit these docs! <https://github.com/OpenDroneMap/docs/blob/publish/source/tutorials.rst>`_
 
 Using Docker
 ^^^^^^^^^^^^