Tools: build option for EKF3 optical flow with SRTM

Author: rmackay9

Tools/scripts/build_options.py

@@ -43,6 +43,7 @@ def config_option(self):
     Feature('AHRS', 'EKF3_EXTNAV', 'EK3_FEATURE_EXTERNAL_NAV', 'Enable External navigation for EKF3', 0, 'EKF3'),
     Feature('AHRS', 'EKF3_WINDEST', 'EK3_FEATURE_DRAG_FUSION', 'Enable Wind estimation for EKF3', 0, 'EKF3'),
     Feature('AHRS', 'EKF3_OPTFLOW', 'EK3_FEATURE_OPTFLOW_FUSION', 'Enable OpticalFlow fusion for EKF3', 0, 'EKF3,OPTICALFLOW'),
+    Feature('AHRS', 'EKF3_OPTFLOW_SRTM', 'EK3_FEATURE_OPTFLOW_SRTM', 'Enable OpticalFlow using SRTM for EKF3', 0, 'EKF3,EK3_FEATURE_OPTFLOW_FUSION'),  # noqa: E501
     Feature('AHRS', 'BARO_WIND_COMP', 'HAL_BARO_WIND_COMP_ENABLED', 'Enable Baro wind compensation', 0, None),
 
     Feature('Safety', 'PARACHUTE', 'HAL_PARACHUTE_ENABLED', 'Enable Parachute', 0, None),

Tools/scripts/extract_features.py

@@ -229,6 +229,7 @@ def __init__(self, filename, nm="arm-none-eabi-nm", strings="strings"):
             ('EK3_FEATURE_EXTERNAL_NAV', r'NavEKF3_core::CorrectExtNavVelForSensorOffset'),
             ('EK3_FEATURE_DRAG_FUSION', r'NavEKF3_core::FuseDragForces'),
             ('EK3_FEATURE_OPTFLOW_FUSION', r'NavEKF3_core::FuseOptFlow'),
+            ('EK3_FEATURE_OPTFLOW_SRTM', r'NavEKF3_core::writeTerrainData'),
 
             ('AP_RC_CHANNEL_AUX_FUNCTION_STRINGS_ENABLED', r'RC_Channel::lookuptable',),
             ('AP_SCRIPTING_ENABLED', r'AP_Scripting::init',),