Write a guide on spatial coordinate systems

[niksirbi]

This issue is branching off #69, because we decided it would make sense to introduce coordinate systems as a standalone guide/page, complete with schematics, similar to what we have for movement datasets.

It could also necessitate adding some additional terms to the glossary, which can be cross-references in this guide.

Contents

A rough list of concepts we'd like to cover:

• Center pixel-aligned systems
• Cartesian vs Polar space
• Image / Camera / World coordinate systems
• Allocentric vs Egocentric systems
• Static vs moving reference frames?
• right hand rule
• Linear algebra:
  • linear transformations
  • origin
  • translation
  • rotation
  • scaling
  • right-hand rule
  • (free) vector

Useful resources

• SLEAP's center pixel-aligned system
• The right hand rule
• free vector
• Freya Holmér's schematic on 3D space and handedness
• Geometry of image formation
• Zulip topics:
  • on coordinate systems and reference frames
  • on movement metrics

[niksirbi]

Here's a long write-up containing my current thoughts on spatial coordinate systems for movement. It contains some background on image formation, the current status quo in movement and some ideas for the future. It's very much a work-in-progress and feedback is welcome.

Spatial coordinate systems.pdf

A cleaned-up and severely shortened version of this will go up on the movement website at some point, as the coordinate system guide. That version will mostly focus on the status quo (already supported systems) rather than future plans.

PS: Some internal document links may have been broken in the process of exporting the PDF from obsidian, but all content is still in there.