Number Precision for SVG
The simplest method to get geographical coordinate from map content is to make geographical coordinate system (Latitude, Longitude) and SVG's coordinate system equivalence.(Though orientation of Y axis is different.) In this case, numerical precision of SVG often causes problems.
For the map of the block level, at least numerical value precision of five decimal point is necessary.
# 0.00001 degree ~ 1 meter
latitude: 123.12345 ... required valid digit number = 8 ( exceeds float...) longitude: 12.12345 ... required valid digit number = 7
However, the minimum requirement of SVG 1.1 is a single precision floating point. It does not meet the requirements mentioned above.
In today's computer, is the single precision floating point proper? ECMA Script requires double precision floating point number.
- number precision of SVG2.0 Editor’s Draft : Number has the capacity for at least a single-precision floating point, conforming High-Quality SVG Viewers are required to use at least double-precision floating point.
- Number value of ECMA-262: IEEE 754 64-bit double-precision
- CSS3 Number : It does not have a floating point description. It does not have an requirement of the precision.