add transforms module

transforms.py

@@ -0,0 +1,41 @@
+import json
+
+import numpy as np
+import pyproj
+
+
+def get_metadata(item):
+    metadata = item["metadata"]
+    if isinstance(metadata, str):
+        metadata = json.loads(metadata)
+    return metadata
+
+
+def lat_lon_mid_pixel(item, subset: str):
+    metadata = get_metadata(item)
+    if subset == "satellogic":
+        crs = metadata["crs"][0]
+        # each image has bounds but they should coincide
+        bounds_crs = metadata["bounds"][0]
+    elif subset == "sentinel_1":
+        crs = metadata["crs"]
+        bounds_crs = metadata["coordinates"][0]
+        assert len(bounds_crs) == 5
+        # bounds are a polygon with same first & last vertex
+        bounds_crs = (
+            bounds_crs[0][0],
+            bounds_crs[0][1],
+            bounds_crs[2][0],
+            bounds_crs[2][1],
+        )
+    else:
+        raise ValueError("subset not known")
+
+    bounds = pyproj.Transformer.from_crs(crs, "EPSG:4326").transform_bounds(*bounds_crs)
+    # dumb average for now
+    return np.array([bounds[0] + bounds[2], bounds[1] + bounds[3]]) / 2
+
+
+def get_google_map_link(item, subset: str):
+    lat, lon = lat_lon_mid_pixel(item, subset)
+    return f"https://www.google.com/maps?ll={lat},{lon}&z=16&t=k"