Adds valid height check for DEM intersection

CHANGELOG.md

@@ -36,5 +36,7 @@ release.
 ## Unreleased
 
 ### Changed
-- Removed all `pyproj` calls from csm.py, abstracting them into the reprojection and pyproj.Transformer code inside utils.py. Updated the transformations to use the new pipeline style syntax to avoid deprecation warnings about old syntax.p
+- Removed all `pyproj` calls from csm.py, abstracting them into the reprojection and pyproj.Transformer code inside utils.py. Updated the transformations to use the new pipeline style syntax to avoid deprecation warnings about old syntax.
 
+### Fixed
+- Added a check to `generate_ground_point` when a GeoDataset is used to raise a `ValueError` if the algorithm intersects a no data value in the passed DEM. This ensures that valid heights are used in the intersection computation.

knoten/csm.py

@@ -170,6 +170,8 @@ def _(dem, image_pt, camera, max_its = 20, tolerance = 0.001):
 
         px, py = dem.latlon_to_pixel(lat, lon)
         height = dem.read_array(1, [px, py, 1, 1])[0][0]
+        if height == dem.no_data_value:
+            raise ValueError(f'No DEM height at {lat}, {lon}')
     
         next_intersection = camera.imageToGround(image_pt, float(height))
         dist = max(abs(intersection.x - next_intersection.x),