Add alignment files page

source/align.rst

@@ -0,0 +1,13 @@
+###############
+Alignment Files
+###############
+
+Georeferencing by default is done using GPS or GCPs (if provided).
+
+Starting from ODM ``3.0.2`` people can supply a reference alignment file to georeference the program outputs. The reconstruction will be initially performed using GPS/GCPs and will subsequently be aligned to the reference model via a linear scaling/rotation/shift operation. 
+
+If you supply a file called ``align.laz``, ``align.las`` or ``align.tif`` (single band GeoTIFF DEM) then ODM will automatically detect it and attempt to align outputs to this reference model. If it has another name you can specify using ``--align <path>``.
+
+The alignment file must be created in the base of your project folder.
+
+`Learn to edit <https://github.com/opendronemap/docs#how-to-make-your-first-contribution>`_ and help improve `this page <https://github.com/OpenDroneMap/docs/blob/publish/source/align.rst>`_!

source/index.rst

@@ -53,6 +53,7 @@ The documentation is available in several languages. Some translations are incom
     gcp
     map-accuracy
     geo
+    align
     masks
     large
     resources