feat: use srtm for disparity if use_srtm is true

Author: roelofvandijkO

s2p/rpc_utils.py

@@ -445,6 +445,9 @@ def exogenous_disp_range_estimation(rpc1, rpc2, x, y, w, h, H1, H2, cfg, A=None,
         disparity is made horizontal thanks to the two rectifying homographies
         H1 and H2.
     """
+    if cfg['exogenous_dem'] is None and cfg.get('exogenous_dem', None) in [None, False]:
+        return
+
     m, M = altitude_range(rpc1, x, y, w, h, cfg, margin_top, margin_bottom)
 
     return altitude_range_to_disp_range(m, M, rpc1, rpc2, x, y, w, h, H1, H2,