# An inverted spatial index for global Tessera embeddings search *2026-10-01 — idea* Status: Ongoing Level: PartII Year: 2026 Project: TESSERA, a pixelwise geospatial foundation model Supervisors: Sadiq Jaffer, Anil Madhavapeddy Students: Minkyum Kim [Tessera](https://anil.recoil.org/projects/tessera) is an open-source, pixel-wise Earth-observation foundation model that compresses a calendar year of Sentinel-2 optical imagery (such as colour and infrared) and Sentinel-1 radar into a 128-dimensional embedding for every 10m pixel on Earth. Since similar surfaces tend to have similar embeddings, nearest-neighbour search can find objects (such as airport runways) from a single example. ## Project outline This project will build and evaluate a query-by-example search index over Tessera embeddings. Given an example set of pixels, such as a port, the index returns the most similar set of pixels in a region. The difficulty is the scale of the embeddings. The UK alone has around 3 billion pixels, and so a brute-force search is too slow for interactive use. The project will therefore explore two questions: - Speed: how fast can query-by-example search be made with an inverted-file index? - Size: how small can the index become through quantisation and truncation without losing too much quality? ## Related - [.plan-26-41: Hello, is it Part II you're looking for?](https://anil.recoil.org/notes/2026w41) (note, 2026-10-11) The Foundations of Computer Science notes are now done as a Forest with live OCaml toplevels, and Part II projects sorted. - [TESSERA, a pixelwise geospatial foundation model](https://anil.recoil.org/projects/tessera) (project, 2025-01-01) --- Canonical: https://anil.recoil.org/ideas/tessera-inverted-spatial-index Type: idea License: CC BY 4.0 Tags: geospatial, embeddings, programming, database