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Geohash a lng/lat coordinate using hilbert space filling curves.

License: MIT License

Python 100.00%
geohash hilbert-curve space-filling-curves geohash-representations longitude latitude

geohash-hilbert's Issues

Cython builds dropped in 1.2.1

Hi!

Thank you for this library, I've been using it for a while.

I noticed that the cython build is not triggered since 1.2.1. I'm using a clean pipenv environ in python 3.7 on a mac:

[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]
cython = "*"

[packages]
geohash-hilbert = "==1.2.0"

[requires]
python_version = "3.7"

(hilbert) ➜  pip freeze
Cython==0.29.16
geohash-hilbert==1.2
(hilbert) ➜  python -c "from geohash_hilbert._hilbert import *; print(CYTHON_AVAILABLE)"
True

(hilbert) ➜  hilbert pipenv install geohash-hilbert==1.2.1
Installing geohash-hilbert==1.2.1…
Adding geohash-hilbert to Pipfile's [packages]…
✔ Installation Succeeded
Pipfile.lock (6bc29a) out of date, updating to (d6a1f1)…
Locking [dev-packages] dependencies…
✔ Success!
Locking [packages] dependencies…
✔ Success!
Updated Pipfile.lock (6bc29a)!
Installing dependencies from Pipfile.lock (6bc29a)…
  🐍   ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 1/1 — 00:00:00
(hilbert) ➜  hilbert python -c "from geohash_hilbert._hilbert import *; print(CYTHON_AVAILABLE)"
False

Still missing in 1.3.1

Installing geohash-hilbert==1.3.1…
Adding geohash-hilbert to Pipfile's [packages]…
✔ Installation Succeeded
Pipfile.lock (26ebc9) out of date, updating to (6bc29a)…
Locking [dev-packages] dependencies…
✔ Success!
Locking [packages] dependencies…
✔ Success!
Updated Pipfile.lock (26ebc9)!
Installing dependencies from Pipfile.lock (26ebc9)…
  🐍   ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 1/1 — 00:00:000:00
(hilbert) ➜  hilbert
(hilbert) ➜  hilbert python -c "from geohash_hilbert._hilbert import *; print(CYTHON_AVAILABLE)"
False

Switching back

(hilbert) ➜  hilbert pipenv install geohash-hilbert==1.2.0
Installing geohash-hilbert==1.2.0…
Adding geohash-hilbert to Pipfile's [packages]…
✔ Installation Succeeded
Pipfile.lock (d6a1f1) out of date, updating to (26ebc9)…
Locking [dev-packages] dependencies…
✔ Success!
Locking [packages] dependencies…
✔ Success!
Updated Pipfile.lock (d6a1f1)!
Installing dependencies from Pipfile.lock (d6a1f1)…
  🐍   ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 1/1 — 00:00:00
(hilbert) ➜  hilbert python -c "from geohash_hilbert._hilbert import *; print(CYTHON_AVAILABLE)"
True

`neighbours` incorrect near poles

It looks like neighbours is incorrect at the poles: it gives the north neighbour of the north pole as the south pole. Here's an example:

In [22]: ghh.encode(0, 89.5, precision=3, bits_per_char=2)
Out[22]: '211'

In [24]: ghh.neighbours("211", bits_per_char=2)
Out[24]:
{'north': '322',
 'north-east': '323',
 'north-west': '011',
 'east': '212',
 'west': '122',
 'south': '210',
 'south-east': '213',
 'south-west': '123'}

In [25]: ghh.decode("322", bits_per_char=2)
Out[25]: (22.5, -78.75)

I guess the notion of neighboring cells is not super well defined at the poles (since all points (longitude, 90) are the same), but I would suggest that a cell which contains the north pole has no north, northwest, or northeast neighbor; likewise for the south pole and south neighbors.

If this seems good I can open a PR.

Add base32 is possible

Hi, it is a suggestion. The main geocodes, like Geohash, use something between base16 and base36 to compress, because for humans and use in resilient protocols we can use alphanumeric codes (no extra-symbols) with case insensitive letters. PlusCode e.g. uses base20, in this range. And the most useful are the base32 variants... Is important to show (here without patents, this is the merit of the open work!) how to offer Hilbert indexation of base32.

As 32×32=1024, we have an exact representation for each two base32 digits. In the Hilbert hierarchical grid terms, it is a "level L5" or "level L+5". So one digit is "L+2.5" (level L+3 minus a half)... It can be represented as "degenerated grid" merging pairs of cells:

The reindexation is necessary only when identifing the cells of the grid, and it is easy, for each cell x, of an index x starting with zero, there are a merged cell i=floor(x).

It is only a problem of spatial interpretation (grid interface construction when need), the base32 geocode existense is independent of a visual grid interface.

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