# Rotations and translations in real time
**URL:** https://discourse.processing.org/t/rotations-and-translations-in-real-time/15490
**Category:** Coding Questions
**Created:** [November 14, 2019, 2:39pm UTC](https://discourse.processing.org/t/rotations-and-translations-in-real-time/15490 "2019-11-14T14:39:15Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Waboqueox](https://discourse.processing.org/u/Waboqueox)
#### Post date: [November 14, 2019, 2:39pm UTC](https://discourse.processing.org/t/rotations-and-translations-in-real-time/15490/1 "2019-11-14T14:39:15Z")
Hi guys, I know there are many topics about this theme, but I’m getting mad with this 🥴…
I have the **UTM coordinates and orientation** of my state, at the same time, I have **coordinates of the objects** that surround me, **referred to my reference system** and it arrives in a **message of other coordinates referred to the same reference system (mine)**.
**I want to find which of the objects that surround me are closer to those coordinates that reach me.**
For this, what I have been trying to do is put everything in the reference system of the UTM coordinates and then calculate the distance between each object and the message coordinates, for this, I have applied these formulas:
```auto
posXtransformed = xOrigin*cos(angle) - yOrigin*sin(angle)) + xUTM;
posYtransformed = xOrigin*sin(angle) + yOrigin*cos(angle)) + yUTM;
```
Once calculated, I calculate the distances with dist (), I run it at a low frequency and it works so or so well, but I need it in real time. Here the problems come, I do not know very well why it is due, but doing tests such as changing the sign of the angle of rotation, it works the same (this I think makes no sense, and that is why I wanted to ask to see if the part of the rotation I am doing right or wrong); and during execution (in real time) sometimes it finds the position well, but then when I rotate my reference system, the object it detects also changes …
Any kind of help is welcome, and sorry for the English, I was having a hard time thinking about how to write the problem and I used the google translator.
---
### Author:  [@jeremydouglass](https://discourse.processing.org/u/jeremydouglass)
#### Post date: [November 22, 2019, 6:27pm UTC](https://discourse.processing.org/t/rotations-and-translations-in-real-time/15490/2 "2019-11-22T18:27:47Z")
> [@Waboqueox](#):
>
> I want to find which of the objects that surround me are closer to those coordinates that reach me.
Did you resolve this issue?
Your phrase “those coordinates that reach me” was unclear.
If you are at position X surrounded by objects A B C and D, are you trying to find the closest object to X, A? Or are you trying to search on A for the closest object to it, B?
A small optimization: In general, if you are trying to optimize an ordered lists of close objects, and not actual distances, do not use dist() – as that is cartesian distance and involves a square root.
> d=√((x1-x2)^2+(y1-y2)^2)
Instead, just use `sq(x1-x2) + sq(y1-y2)`. This gives the squared distance, which is still fine for sorting and identifying the closest object. (I’m assuming that you have a _lot_ of objects). Depending on your precision you could also do this as integers. If you have a proximity distance threshhold, you can square the proximity and compare it to your squared distance list as a cutoff.
---
### Author:  [@Waboqueox](https://discourse.processing.org/u/Waboqueox)
#### Post date: [December 2, 2019, 11:13am UTC](https://discourse.processing.org/t/rotations-and-translations-in-real-time/15490/3 "2019-12-02T11:13:50Z")
> [@jeremydouglass](#):
>
> Did you resolve this issue?
Mmm maybe 🤔, not sure yet, I found that I was dragging some rotations and the visualization wasn’t correct, but the calculation seems yes.
> [@jeremydouglass](#):
>
> If you are at position X surrounded by objects A B C and D, are you trying to find the closest object to X, A? Or are you trying to search on A for the closest object to it, B?
I get a point P and want to find the closest object to it ( P ) (dist P to A, P to B…), P is referring to my X position, but just have the update coordinates of P when the message reach to my system (and want to conserve that coordinates even when X moves)
> [@jeremydouglass](#):
>
> Instead, just use `sq(x1-x2) + sq(y1-y2)` . This gives the squared distance, which is still fine for sorting and identifying the closest object. (I’m assuming that you have a _lot_ of objects). Depending on your precision you could also do this as integers. If you have a proximity distance threshold, you can square the proximity and compare it to your squared distance list as a cutoff
😊 Thanks, will try it, my amount of objects is variable, sometimes I have less and sometimes more.
By the way I have to correct some issues before I can try it 😅.