better flying recommendations

source/flying.rst

@@ -1,6 +1,30 @@
 Flying Tips
 ===========
 
+Data collection effort, full 3D
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+For best in class results with full 3D reconstruction, we recommend the following:
+
+* 60% overlap nadir flight
+* 70-80% overlap 45-degree gimbal angle cross-grid
+
+The 45-degree cross-grid flight provides the basis for a fully tied together model, while the nadir flights provide the necessary texture for orthophoto texturing. The lower overlap  meets the minimum requirement for orthophoto products as facilitated by by feature matching from the much higher overlap cross-grid.
+
+Data collection effort, 2D and 2.5D products
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+For best in class results 2D and 2.5D products and 5cm resolution, we recommend the following:
+
+* 70-80% overlap slightly off-nadir (5-10 degree off nadir)
+
+For more complex buildings and vegetation, aim for closer to 80-83% overlap. If buildings, vegetation, and terrain changes are not complex, it's quite feasible to use closer to 70% overlap.
+
+(credit: derived from ongoing conversations with Ivan Gayton, Humanitarian OpenStreetMap Team)
+
+Other resources on flying:
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 The `Humanitarian OpenStreetMap team <https://www.hotosm.org/>`_ has guidelines on `flying for UAV mapping <https://uav-guidelines.openaerialmap.org/>`_:
 
 - `Choosing the right UAV <https://uav-guidelines.openaerialmap.org/pages/05-choosing-the-right-uav/>`_ 
@@ -15,5 +39,4 @@ See also DroneDeploy's guide on `Making Successful Maps <https://support.dronede
 
 Finally, lens distortion is a challenge in projects requiring accurate 3D data. See our section in these docs on `Camera Calibration </tutorials/#calibrating-the-camera>`_.
 
-
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