Add enums for GMT grid format ID and only add the Conventions for net…

…CDF files

doc/api/index.rst

@@ -242,6 +242,14 @@ In addition, there is also a special function to load XYZ tile maps via
 
 .. currentmodule:: pygmt
 
+Enumerations
+------------
+
+.. autosummary::
+    :toctree: generated
+
+    enums
+
 Exceptions
 ----------
 

pygmt/datatypes/header.py

@@ -6,6 +6,7 @@
 from typing import Any, ClassVar
 
 import numpy as np
+from pygmt.enums import GridID
 
 # Constants for lengths of grid header variables.
 #
@@ -203,7 +204,14 @@ def data_attrs(self) -> dict[str, Any]:
         Attributes for the data variable from the grid header.
         """
         attrs: dict[str, Any] = {}
-        attrs["Conventions"] = "CF-1.7"
+        if self.type in {  # netCDF format
+            GridID.GMT_GRID_IS_NB,
+            GridID.GMT_GRID_IS_NS,
+            GridID.GMT_GRID_IS_NI,
+            GridID.GMT_GRID_IS_NF,
+            GridID.GMT_GRID_IS_ND,
+        }:
+            attrs["Conventions"] = "CF-1.7"
         attrs["title"] = self.title.decode()
         attrs["history"] = self.command.decode()
         attrs["description"] = self.remark.decode()

pygmt/enums.py

@@ -0,0 +1,39 @@
+"""
+Enumerations for PyGMT.
+"""
+
+from enum import IntEnum
+
+
+class GridID(IntEnum):
+    """
+    Enum for the GMT grid format ID.
+
+    These enums are defined in 'gmt_grdio.h'.
+    """
+
+    GMT_GRD_UNKNOWN_FMT = 0  # If grid format cannot be auto-detected
+    GMT_GRID_IS_BF = 1  # GMT native, C-binary format (32-bit float)
+    GMT_GRID_IS_BS = 2  # GMT native, C-binary format (16-bit integer)
+    GMT_GRID_IS_RB = 3  # SUN rasterfile format (8-bit standard)
+    GMT_GRID_IS_BB = 4  # GMT native, C-binary format (8-bit integer)
+    GMT_GRID_IS_BM = 5  # GMT native, C-binary format (bit-mask)
+    GMT_GRID_IS_SF = 6  # Golden Software Surfer format 6 (32-bit float)
+    GMT_GRID_IS_CB = 7  # GMT netCDF format (8-bit integer, depreciated)
+    GMT_GRID_IS_CS = 8  # GMT netCDF format (16-bit integer, depreciated)
+    GMT_GRID_IS_CI = 9  # GMT netCDF format (32-bit integer, depreciated)
+    GMT_GRID_IS_CF = 10  # GMT netCDF format (32-bit float, depreciated)
+    GMT_GRID_IS_CD = 11  # GMT netCDF format (64-bit float, depreciated)
+    GMT_GRID_IS_RF = 12  # GEODAS grid format GRD98 (NGDC)
+    GMT_GRID_IS_BI = 13  # GMT native, C-binary format (32-bit integer)
+    GMT_GRID_IS_BD = 14  # GMT native, C-binary format (64-bit float)
+    GMT_GRID_IS_NB = 15  # GMT netCDF format (8-bit integer)
+    GMT_GRID_IS_NS = 16  # GMT netCDF format (16-bit integer)
+    GMT_GRID_IS_NI = 17  # GMT netCDF format (32-bit integer)
+    GMT_GRID_IS_NF = 18  # GMT netCDF format (32-bit float)
+    GMT_GRID_IS_ND = 19  # GMT netCDF format (64-bit float)
+    GMT_GRID_IS_SD = 20  # Golden Software Surfer format 7 (64-bit float, read-only)
+    GMT_GRID_IS_AF = 21  # Atlantic Geoscience Center format AGC (32-bit float)
+    GMT_GRID_IS_GD = 22  # Import through GDAL
+    GMT_GRID_IS_EI = 23  # ESRI Arc/Info ASCII Grid Interchange format (ASCII integer)
+    GMT_GRID_IS_EF = 24  # ESRI Arc/Info ASCII Grid Interchange format (ASCII float)