Estimating the speed of the ISS using computer vision (Python + OpenCV)

BabbaWaagen — Tue, 31 Mar 2026 17:13:51 +0000

Estimating the speed of the ISS using computer vision

I recently revisited an older project I built with a friend for a school project as part of the ESA Astro Pi 2024 challenge.

The idea was simple:

estimate the speed of the ISS using only images of Earth.

Approach

The project is written in Python using OpenCV.

The pipeline looks like this:

capture two images
detect keypoints using SIFT
match them using FLANN
measure pixel displacement
convert that into real-world distance (GSD)
calculate speed based on time difference

Result

Estimated speed:
~7.47 km/s

Actual ISS speed:
~7.66 km/s

So roughly a 2–3% difference.

Not perfect, but surprisingly close considering it’s based purely on image analysis.

Limitations

The original runtime images are unfortunately lost, so the repository mainly contains test/template images.

This obviously limits how well the results can be reproduced.

What I would improve

Looking at it now, I would:

improve filtering of bad matches
make the pipeline cleaner
handle outliers more robustly

Repo

https://github.com/BabbaWaagen/AstroPi

If you’ve worked with similar approaches or have ideas on improving matching quality, I’d be interested.

Auditing repository bloat without auto-fixing anything

BabbaWaagen — Mon, 09 Feb 2026 14:41:41 +0000

Repository Cleanup and Auditing

Over time, repositories tend to accumulate things that were never part of the original plan.

Not necessarily because someone made a mistake, but because repos live for years:

build outputs get committed temporarily
files get copied instead of reused
directories stick around after refactors
ownership changes and context gets lost

None of this is dramatic on its own — but over time it adds up.

The Problem I Ran Into

I wanted a way to see the current state of a repository without:

deleting anything
rewriting history
enforcing opinions
adding heavy configuration

Most tools I tried either focused on auto-cleanup or required a lot of setup.
I just wanted an audit.

A Small CLI for Repo Audits

So I built a small CLI tool in Go called repo-clean.

It scans a repository and reports:

large files
duplicate files (by hash)
commonly unwanted directories

It does not:

auto-delete files
modify the repo
push best practices
hide details

It only reports what is already there.

Example Usage

repo-clean scan .

For CI or automation, JSON output is available:

repo-clean scan . --json

This makes it easy to plug into pipelines, reports, or checks without changing developer workflows.

Why No Auto-Fixes?

This is a deliberate choice.

In many teams, especially with older or shared repositories:

not everything can be removed immediately
some artifacts are temporarily tolerated
decisions require human context

repo-clean is meant to surface information, not make decisions.

When This Is Useful

This tool is intentionally narrow, but works well for:

legacy repositories
CI audits
periodic repo hygiene checks
understanding why a repo feels heavier over time

It is not a replacement for .gitignore or good Git practices.
It's an audit tool for the current state.

Open Source

The project is open source (MIT):

https://github.com/Bladiostudio/repo-clean

Feedback, issues, and improvements are welcome.

DEV Community: BabbaWaagen