Chris Hill-Scott 738ac1d818 Vary bleed amount based on population density
There are basically two kinds of 4G masts:

Frequency | Range       | Bandwidth
----------|-------------|----------------------------------
800MHz    | Long (500m) | Low (can handle a bit of traffic)
1800Mhz   | Short (5km) | High (can handle lots of traffic)

The 1800Mhz masts are better in terms of how much traffic they can
handle and how fast a connection they provide. But because they have
quite short range, it’s only economical to install them in very built up
areas†.

In more rural areas the 800MHz masts are better because they cover a
wider area, and have enough bandwidth for the lower population density.

The net effect of this is that cell broadcasts in rural areas are likely
to bleed further, because the masts they are being broadcast from are
less precise.

We can use population density as a proxy for how likely it is to be
covered by 1800Mhz masts, and therefore how much bleed we should expect.
So this commit varies the amount of bleed shown based on the population
density.

I came up with the formula based on 3 fixed points:
- The most remote areas (for example the Scottish Highlands) should have
  the highest average bleed, estimated at 5km
- An town, like Crewe, should have about the same bleed as we were
  estimating before (1.5km) – Pete D thinks this is about right based on
  his knowledge of the area around his office in Crewe
- The most built up areas, like London boroughs, could have as little as
  500m of bleed

Based on these three figures I came up with the following formula, which
roughly gives the right bleed distance (`b`) for each of their population
densities (`d`):
```
b = 5900 - (log10(d) × 1_250)
```

Plotted on a curve it looks like this:

This is based on averages – remember that the UI shows where is _likely_
to receive the alert, based on bleed, not where it’s _possible_ to
receive the alert.

Here’s what it looks like on the map:

---

†There are some additional subtleties which make this not strictly true:
- The 800Mhz masts are also used in built up areas to fill in the gaps
  between the areas covered by the 1800Mhz masts
- Switching between masts is inefficient, so if you’re moving fast
  through a built up area (for example on a train) your phone will only
  use the 800MHz masts so that you have to handoff from one mast to
  another less often
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notifications-admin

GOV.UK Notify admin application - https://www.notifications.service.gov.uk/

  • Register and manage users
  • Create and manage services
  • Send batch emails and SMS by uploading a CSV
  • Show history of notifications

Setting up

Python version

At the moment we run Python 3.6 in production.

NPM packages

brew install node

NPM is Node's package management tool. n is a tool for managing different versions of Node. The following installs n and uses the long term support (LTS) version of Node.

npm install -g n
n lts

environment.sh

In the root directory of the application, run:

echo "
export NOTIFY_ENVIRONMENT='development'
export FLASK_APP=application.py
export FLASK_ENV=development
export WERKZEUG_DEBUG_PIN=off
"> environment.sh

AWS credentials

To run parts of the app, such as uploading letters, you will need appropriate AWS credentials. See the Wiki for more details.

To run the application

# install dependencies, etc.
make bootstrap

# run the web app
make run-flask

Then visit localhost:6012.

To test the application

# install dependencies, etc.
make bootstrap

make test

Common tasks

Updating application dependencies

requirements.txt is generated from the requirements.in in order to pin versions of all nested dependencies. If requirements.in has been changed, run make freeze-requirements to regenerate it.

Automatically rebuild the frontend assets

If you want the front end assets to re-compile on changes, leave this running in a separate terminal from the app

    npm run watch

Further docs

Description
The UI of Notify.gov
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