https://github.com/ppkrauss/sfc4q
Space-filling curve valid to index hierarchical grid of aperture-4 quadrilateral cells
https://github.com/ppkrauss/sfc4q
geocode hierarchical-grids quadrilateral-cells space-filling-curves
Last synced: 5 months ago
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Space-filling curve valid to index hierarchical grid of aperture-4 quadrilateral cells
- Host: GitHub
- URL: https://github.com/ppkrauss/sfc4q
- Owner: ppKrauss
- Created: 2019-10-05T11:54:15.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2022-09-26T00:02:16.000Z (over 3 years ago)
- Last Synced: 2025-02-12T11:14:05.439Z (over 1 year ago)
- Topics: geocode, hierarchical-grids, quadrilateral-cells, space-filling-curves
- Language: JavaScript
- Homepage: https://ppkrauss.github.io/Sfc4q/
- Size: 629 KB
- Stars: 0
- Watchers: 1
- Forks: 1
- Open Issues: 4
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Metadata Files:
- Readme: README.md
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README
[](https://zenodo.org/badge/latestdoi/212991020)
([click here to online demonstration](https://ppkrauss.github.io/Sfc4q/) for Desktop Firefox or Chrome)
# Sfc4q classes
*Space-filling curves* (SFCs) can be used to index discrete grids, including the [Geospatial ones](http://docs.opengeospatial.org/as/15-104r5/15-104r5.html). Each cell in the grid is associated with an index, which can be produced by an SFC. In this project, we are particularly interested in hierarchical grids with a recurring partition of quadrilateral cells in 4 regions:
Therefore, we are interested in any SFC that is valid for indexing hierarchical grid of refinement-ratio-4 quadrilateral cells, abbreviated **SFC-4q**, or *Sfc4q* as adopted in the project's name and classes names.
In this project we are also interested in [geocodes](https://en.wikipedia.org/wiki/Geocode) obtained by labeling the SFC indexes, expressing it in human-readable **hierarchical codes**. The hierarchy of the code is illustrated above as the commom prefix (e.g. `2` in `20` and `23`) that emerges in with the base4 representation.
## Framework organization
The framework can be used as simple standard interface for a set of SFC algorithms, like Hilbert, Morton or other.
The algorithms themselves are "concrete classes". But the standardization of basic methods, such as *endode()* and *decode()*, is not the issue, there are a lot of generic and reusable methods, so the best way is to extend a generic class with these reusable methods, and implement the concrete algorithm as specialization. This project is a set of abstract and concrete classes.
Other important issue for SFC-4q is the generalization for "half levels" described in [this PDF article](https://zenodo.org/record/2536584). It is also independent of the concrete algorithms. The illustration bellou is hou these classes uas implemented:
* [**GSfc4q**](https://ppkrauss.github.io/Sfc4q/docs/jsDocs/GSfc4q.html): the "Generalized Sfc4q" class.
* [**GSfc4qLbl**](https://ppkrauss.github.io/Sfc4q/docs/jsDocs/GSfc4qLbl.html): a generaliation of GSfc4q, to translate *key*, *bkey* and cell identifiers (cell IDs) into human-readable labels (lbl). To preserve hierarchy, this translation uses the concept of [Natural Codes](http://osm.codes/_foundations/art1.pdf), implemented in Javascript by the class SizedBigInt.
* **GSfc4qLbl_Hilbert**: the "concrete class" that implements the [Hilbert curve](https://en.wikipedia.org/wiki/Hilbert_curve).
* **GSfc4qLbl_Morton**:the "concrete class" that implements the [Morton curve](https://en.wikipedia.org/wiki/Z-order_curve) (also Z-order curve).
* [**SizedBigInt**](https://ppkrauss.github.io/Sfc4q/docs/jsDocs/SizedBigInt.html): it is a complementar tool for use BigInt (mainly 64 bits unsigned integers) as hierarchical indexes and obtain its string representations, and an implementation of the Natural Codes.
See [classes documentation](https://ppkrauss.github.io/Sfc4q/docs/jsDocs).
## The grid and D3 peparation classes
* [**GridOfCurve**](https://ppkrauss.github.io/Sfc4q/docs/jsDocs/GridOfCurve.html)
* [**GridOfCurve_D3**](https://ppkrauss.github.io/Sfc4q/docs/jsDocs/GridOfCurve_D3.html)
## LICENSE
Content, data and algorithms: **CC0 1.0**, Public Domain Dedication.
[](http://creativecommons.org/publicdomain/zero/1.0)