Build it yourself

Build a map app for one person's own neighbourhood. It records the small places where they go to catch their breath, which it calls sanctuaries, and it finds one when they need it. It works offline, and everything stays on their device.

Build it in these six parts.

1. A database that is a file
Use SQLite in the browser, through wa-sqlite or sql.js with an OPFS backend. It is one file the person can export, copy to a USB stick, or delete. No account exists.

2. A page that opens with nothing behind it
Make it a static progressive web app. Add a manifest with display set to standalone, and a service worker that caches the shell so the app opens in flight mode. Fetch nothing at start-up.

3. A position, used and discarded
Read the position with navigator.geolocation.getCurrentPosition at the moment the person asks, and never write it anywhere. Compute the bounding box for the search from it, then throw both away.

4. Capture that takes five seconds
Build one screen for logging a spot: a name, three sliders and two toggles. Logging a spot must take less time than sitting down on it, or nobody will log anything and the map stays empty.

5. A backup the person can hold
Let the person export the .sqlite file. That is the whole backup.

6. Nothing else
Do not add a sync service, an account, a share button or a feed. Each one turns a private map into a public one.

Create the database with this schema. It has three tables: a place, what that place is like, and what it was like each time the person went. Keep the third one. It is what makes the map get better instead of just longer.

-- One file. This is the whole database.
CREATE TABLE sanctuaries (
    id         TEXT PRIMARY KEY,   -- uuid, so two devices never collide
    latitude   REAL NOT NULL,
    longitude  REAL NOT NULL,
    name       TEXT,
    created_at INTEGER NOT NULL
);

CREATE TABLE profiles (
    id             TEXT PRIMARY KEY,
    sanctuary_id   TEXT NOT NULL,
    noise_level    INTEGER,   -- 1 silent .. 5 traffic
    visual_privacy INTEGER,   -- 1 exposed .. 5 hidden
    foot_traffic   INTEGER,
    sun_exposure     TEXT,
    wind_block       BOOLEAN,
    ground_condition TEXT,
    has_seating      BOOLEAN,
    seating_quality  INTEGER,
    FOREIGN KEY (sanctuary_id) REFERENCES sanctuaries(id)
);

CREATE TABLE visits (
    id           TEXT PRIMARY KEY,
    sanctuary_id TEXT NOT NULL,
    visited_at   INTEGER NOT NULL,
    season       TEXT,
    time_of_day  TEXT,
    note         TEXT,
    FOREIGN KEY (sanctuary_id) REFERENCES sanctuaries(id)
);

CREATE INDEX idx_lat_lon ON sanctuaries(latitude, longitude);

To find a place, search for sanctuaries with a noise level of 2 or under and a visual privacy of 4 or over, inside a box around where the person is standing, and sort the results by distance on the device. Use this query, and fill :lat and :lon from the position and :d from the size of the box:

-- Low noise and high visual privacy, inside a box around the person.
SELECT s.name, s.latitude, s.longitude
  FROM sanctuaries s
  JOIN profiles p ON p.sanctuary_id = s.id
 WHERE p.noise_level <= 2
   AND p.visual_privacy >= 4
   AND s.latitude  BETWEEN :lat - :d AND :lat + :d
   AND s.longitude BETWEEN :lon - :d AND :lon + :d;

The query does not sort. Work out the distance to each result in the app, and sort by it there.