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[netCDFJava #CSV-442004]: Projection false easting and false northing conversion

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  • Subject: [netCDFJava #CSV-442004]: Projection false easting and false northing conversion
  • Date: Wed, 15 Oct 2014 12:01:06 -0600
Greetings Brieuc,

Thanks for your feedback. Unfortunately, this part of the netcdf-java code 
base was written before the conventions were in place, and to change the 
behavior at this point would require a substantial rewrite (we have checked
into it before for the reasons you mention).

Cheers,

Sean

> Hi there,
> 
> My name is Brieuc. I'm working to add support for NetCDF dataset in our
> products.
> 
> I am a bit puzzled by some code in
> AbstractCoordTransBuilder.getFalseEastingScaleFactor(...): this method
> first fetch the unit from the GeoX axis, and if present, return the
> scale factor  to convert one count of this unit into kilometers, if not
> present return 1.0:
> 
> String units = ...; // fetch from grid mapping variable or GeoX axis
> 
> if (units != null) {
> try {
> SimpleUnit unit = SimpleUnit.factoryWithExceptions(units);
> return unit.convertTo(1.0, SimpleUnit.kmUnit);
> } catch (Exception e) {
> log.error(units + " not convertible to km");
> }
> }
> return 1.0;
> 
> This make the behaviour of method a little bit unpredictable. I'm not
> sure if all supported conventions (COARDS, CF...) require a unit
> attribute on GeoX and GeoY axes (or what would be the default unit if
> not present) but now we have:
> 
> - unit present -> false easting and false northing converted from
> whatever length unit is specified into km
> - unit not present -> false easting and false northing unit is unknow
> 
> Wouldn't it be more consistent if we assume metre as default and convert
> to metre (instead of km) if unit if present. Hence we could safely
> assume that ProjectoinImpl "false_easting" and "false_northing"
> parameter would be expressed in metre.
> 
> Thanks for your feedback.
> 
> Regards
> 
> Brieuc DESOUTTER
> Senior Software Engineer
> Luciad NV
> 
> 

Ticket Details
===================
Ticket ID: CSV-442004
Department: Support netCDF Java
Priority: High
Status: Open