Changes between Version 15 and Version 16 of NetCDF_ProjectionTestingStatus

Timestamp:

Oct 23, 2011, 6:55:22 PM (13 years ago)

Author:

pds

Comment:

Revised notes re LCC-1SP

NetCDF_ProjectionTestingStatus

@@ -15 +15 @@
 ||AE||Azimuthal equidistant||Yes||Yes||No||18/10/11||See (1) below||
 ||LAEA||Lambert azimuthal equal area||Yes||Yes||Yes||18/10/11||||
-||LCC1SP||Lambert conformal||?||?||?||18/10/11||See note below.||
+||LCC1SP||Lambert conformal||Yes*||Yes*||?||18/10/11||See note below.||
 ||LCC2SP||Lambert conformal||Yes||Yes||Yes||18/10/11||||
 ||CEA||Lambert Cylindrical Equal Area||Yes||Partial||No||18/10/11||Tested regular OGC WKT with std_parallel version (CF-1 has alternative scale_factor_at_projection_origin version, see notes below). See (1) below re NetCDF-Java loading.||
@@ -35 +35 @@
  * AEA : The OGC WKT version has 2 Std parallels - whereas the CF-1.5 version says it can have either 1 or 2 std parallels. How should the CF 1SP version be converted to OGC WKT, and vice-versa? 
   * Currently the driver, on import and finding an AEA with only 1 std parallel, will set the 2nd std parallel in the WKT as identical to the first.
- * LCC : The OGC WKT 'Lambert_Conformal_Conic_2SP' maps clearly to LCC in CF-1 with 2 std parallels. The CF-1 spec claims that a 1SP version can be used, but it doesn't include a 'scale_factor' as does the OGC WKT 'Lambert_Conformal_Conic_1SP'. Is mapping std_parallel_1 maps to latitude_of_origin and setting scale_factor=1 correct? (see bug #3324)
+ * LCC : The OGC WKT 'Lambert_Conformal_Conic_2SP' maps clearly to LCC in CF-1 with 2 std parallels. The CF-1 spec claims that a 1SP version can be used, but it doesn't include a 'scale_factor' as does the OGC WKT 'Lambert_Conformal_Conic_1SP'. 
+  * For import: Given discussion and example on #3324, and also support from NARCCAP project: it seems the CF-1 LCC 1SP projection is a 'degenerate' LCC-2SP with both SP's at the same location. Thus seems we can read with both 'std_parallel' (1 value) and 'latitude_of_projection_origin' mapping to latitude_of_origin (WKT) and setting scale_factor=1? This is the code's current behaviour (though perhaps could do more error-checking).
+  * For export: given the LCC-1SP can specifically include a scale_factor to control the projection (see http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_1sp.html), it seems this can't be directly exported to NetCDF without throwing away the scale factor.
+    * Perhaps the reasonable thing for now is to export the scale_factor to NetCDF, so it can at least be read back in. Otherwise, we'd have to try to translate the LCC-1SP to a LCC-2SP on the fly.
  * CEA : The CF-1 conventions claim this can be encoded with a 'scale_factor_at_projection_origin' alternative to standard parallel - how would this conversion be done back from OGC WKT?
  * PS : This projection's parameters in CF-1 are significantly different from http://www.remotesensing.org/geotiff/proj_list/polar_stereographic.html. In particular the CF-1 equivalent for 'latitude of natural origin' seems to be 'standard_parallel'. Note: we have verified the current approach we take to mapping is the same used by at least one other NetCDF CF-1 user in the UCAR NARCCAP project.