[postgis-devel] GeoJSON Precision

[Even Rouault]

On mardi 7 mai 2019 16:17:15 CEST Paul Ramsey wrote:
> This blog post reminded me:
> 
> https://rapidlasso.com/2019/05/06/how-many-decimal-digits-for-storing-longit
> ude-latitude/
> <https://rapidlasso.com/2019/05/06/how-many-decimal-digits-for-storing-long
> itude-latitude/>
> 
> GeoJSON generation uses DBL_DIG as the number of decimal places, which is… a
> lot? 15 or 16 depending on your platform. I wonder if maybe we should crank
> that down to 8 as the default and let people crank it *up* as desired
> rather than emitting nanometer precision and expecting people to crank it
> *down* (they don’t).

For what is worth, https://tools.ietf.org/html/rfc7946 mentions in  11.2.  
Coordinate Precision

"""
For geographic coordinates with units of degrees, 6 decimal places (a default 
common in, e.g., sprintf) amounts to about 10 centimeters, a precision well
within that of current GPS systems.
"""

Looking at GDAL implementation of RFC7946, I see we are actually using 7 
decimals.

Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com