[PROJ] Syntax to change projection from UTM to TM

[Charles Karney]

On 12/9/24 3:06 PM, Javier Jimenez Shaw via PROJ wrote:
> What always make me nuts is the false easting and northing. They are 
> just to have positive numbers in your coordinates (it is just adding an 
> offset to the final numbers). I am never sure if they are "real" meters 
> or "distorted" meters (I think the latter).

I sympathize!  However there's a sound reason for having all the
coordinates positive, namely computing their differences is more
systematic.  If one of the numbers is negative you have to switch to the
rules for addition.  (We're talking about hand calculations here, of
course.)

I'm old enough to have used log tables and there was a similar
notational trick here.  Thus log(2) = 0.3 (these are common logs) and so
log(0.2) = 0.3 - 1 = -0.7.  But when multiplying a bunch of numbers,
i.e., adding a bunch of logs, you don't want a few of them to be
negative.  So log(0.2) was written either as

   bar1 . 3  (bar1 means -1 only in the units place), or
   9 . 3 (10 added to negative logs)

[Yes, the false easting and northing are distorted meters.]

-- 
Charles Karney <karney at alum.mit.edu>
702 Prospect Ave
Princeton, NJ 08540-4037