### Thales GEO/R

Well, obviously I needed this calculator to complete my collection of GEO’s.

When it appeared on ebay at an attractive price, I couldn’t resist. This is the first one, and this the second and third ones, serial nr. 60533 and 67546. The Thales GEO was the geodetic calculator designed and marketed by Thales. This later model, n° 159874, has a few features that the earlier ones did not have. The gearbox is put together differently, which instead of only allowing both machines in the same and opposite directions, in this machine you can also switch either machine off independently, so it doesn’t rotate along with the handle. In the earlier ones, you can only do that with the left machine. There are also indicators for the direction any register (setting and counter) is rotating in: +, - or neutral. But the main improvement is that this machine is now equipped with back transfer from the result to the input. I’ve given it a bit of a trial run with my favourite geodetic calculation, so I pitched the earlier Thales against the later one, to see how much time the back transfer will save you in an origin shift ... let’s see!

We start with coordinates x = 4.58432 and y = 2.17821 The new origin in the old coordinate system will be x = 0.02231 and y= -0.12735 To give 4.65201 and 2.30556 as the starting coordinates, and the rotation of the grid is discussed here.

So what about the timing with the back transfer feature?

**Old machine:**

setting 25s

resetting 35s

resetting result **30s**

1st multiplication 45s

2nd multiplication 50s

3rd multiplication 40s

**New (this) machine:**

setting 25s

resetting 41s

resetting result **24s**

1st multiplication 49s

2nd multiplication 45s

3rd multiplication 20s

Brilliant - that back transfer functionality saves you all of 6 seconds! I guess it’s the thought that counts... Here’s the video:

For ideas on what it can be used for, and how, see the page on geodetic calculators.

And with that, here are the pictures of this nice calculator “dans son jus”:

And of course the whole family together for a group shot!