Add altitude, landcover, and landseamask to mersi_ll_l1b reader

AUTHORS.md

@@ -38,6 +38,7 @@ The following people have made contributions to this project:
 - [Gerrit Holl (gerritholl)](https://github.com/gerritholl) - Deutscher Wetterdienst
 - [David Hoese (djhoese)](https://github.com/djhoese)
 - [Marc Honnorat (honnorat)](https://github.com/honnorat)
+- [Chung-Hsiang Horng(chorng)](https://github.com/chorng)
 - [Mario Hros (k3a)](https://github.com/k3a)
 - [Lloyd Hughes (system123)](https://github.com/system123)
 - [Sara Hörnquist (shornqui)](https://github.com/shornqui)

satpy/etc/readers/mersi_ll_l1b.yaml

@@ -272,3 +272,27 @@ datasets:
     coordinates: [longitude, latitude]
     file_type: mersi_ll_l1b_1000_geo
     file_key: Geolocation/MoonAzimuth
+  altitude:
+    name: altitude
+    units: degree
+    standard_name: altitude
+    resolution: 1000
+    coordinates: [longitude, latitude]
+    file_type: mersi_ll_l1b_1000_geo
+    file_key: Geolocation/Altitude
+  landcover:
+    name: landcover
+    units: degree
+    standard_name: landcover
+    resolution: 1000
+    coordinates: [longitude, latitude]
+    file_type: mersi_ll_l1b_1000_geo
+    file_key: Geolocation/LandCover
+  landseamask:
+    name: landseamask
+    units: degree
+    standard_name: landseamask
+    resolution: 1000
+    coordinates: [longitude, latitude]
+    file_type: mersi_ll_l1b_1000_geo
+    file_key: Geolocation/LandSeaMask