Bad computation with lambert 2 extended

[xavierlecomte]

Hi,

thank for your work,
I have a issue with lambert 2 Ext. transformation

sample :
876962.7 2084698.5
with API : lat 45.706205 5.894071

With http://tool-online.com/conversion-coordonnees.php lat 45.70621767 5.89416135 => OK

can you have a look of this ?

thanks

[yageek]

I have the same problem with the variant of this library on the other language. I don't know if this lack of precision is due to the algorithm or the rounding done during the different phases (or both).

But the problem, is also to have a reference, how to know which tool has the right coordinates and with which precision.

Do you know any tool or values we can take as references ?

[xavierlecomte]

Hi,
thank you for your answer.

In Fact, i work on transportation project with 2 different file format generated by an external system:

• Original format with lambert II
• Other format with lat / lon BUT i cannot use it for my projet.

In this interface (i have not the algorithme) , the stop point "Alfred De Vigny" is converted from
876962.7; 2084698.5 => 45.706219, 5.894161

the result is quite similar than web site (45.706218 , 5.894161) but different with the API (45.706205 5.894071)

if its possible to increase the precision it would be very nice

[yageek]

It may be interesting to see if the precision is due to rounding and not algorithm. We should make a branch an use this library : http://www.apfloat.org/apfloat_java/ to check if we improve precision. As soon I have time, I will try to. Help is welcome.