distance calculations

background

System has a need to calculate distance information between addresses.

Address table has latitude/longitude pairs along with normalizaed address information. This information is pulled from mapbox.

code

Command core:travel-distance will calculate driving distance and driving time estimates from mapbox by iterating through a collection of to/from address pairs.

core:travel-distance {--user=all} {--to=all} {--sleep=1} {--max-mileage=150}

The –user param takes a user ID or email, and will use the user address on file as the first address. If ‘all’ is selected, all user addresses will be iterated over.

When iterating over one or more user addresses, the ‘to’ parameter is inspected. One or more hospital site addresses will be paired against the user address.

The lat/lon of the pair will be compared with a distance estimating function, and pairs that are under the ‘max-mileage’ parameter will be calculated.
Pairs that exceed the max-mileage estimate will be skipped. This will prevent generally unhelpful values from being calculated (saving time and api calls) - knowing that the drive time from Connecticut to Tennessee is 11 hours generally hot helpful for the ‘drive time’ use case.

When a site address is updated, the system will attempt to update distances table with the new site address against all doctor pairs (subject to the max-mileage estimate).

When a user address is updated, the system will attempt to update distances table with the new user address against all hospital address pairs (subject to the max-mileage estimate).

When updating a user or site address distance combination, the previous distance information is deleted before the api call is made. This was to avoid a new known address displaying previously calculated and potentially ‘wrong’ information.

If the estimated mileage is over the cutoff range, we’ll store just the estimated mileage and a -1 in the ‘seconds’ time. This will indicate that the mileage is rough ‘great circle’ estimate.

config

config/core.php has ‘max-mileage-estimate’ which is referenced via

```php config(‘core.max-mileage-estimate’) ````

The default value is 150, but can be overridden with an environment key of MAX_MILEAGE_ESTIMATE