# Adding fiducial marks and determining RAS coordinates

**URL:** https://discourse.slicer.org/t/adding-fiducial-marks-and-determining-ras-coordinates/13421
**Category:** Development
**Created:** [September 10, 2020, 12:58pm UTC](https://discourse.slicer.org/t/adding-fiducial-marks-and-determining-ras-coordinates/13421 "2020-09-10T12:58:54Z")
**Posts on this page:** 1
**Page:** 2

<div class="post-metadata">

### Author: ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [October 9, 2020, 1:47pm UTC](https://discourse.slicer.org/t/adding-fiducial-marks-and-determining-ras-coordinates/13421/21 "2020-10-09T13:47:50Z")

</div>

Most of Slicer core is implemented in C++ and most module widgets are composed of various Qt, CTK, and Slicer widgets. You can edit the GUI using Qt designer. You can use any of the C++ loadable modules in Slicer core as an example of adding observers and connections.

[Previous page](https://discourse.slicer.org/t/adding-fiducial-marks-and-determining-ras-coordinates/13421.md?page=1)