# [OSRM-talk] 'penalty' for snapping

Tue Apr 19 20:31:38 UTC 2016

```Use a wrigglefactor:

Say a persons needs to deviate from straight line with a factor of:

- x 1.2 on flat land
- x 4.0 in mountains and swamps

and calculate with a walking speed of:

- 3.5 km/h in fields
- 2.3 km/h in closed forests
- 1.2 km/h in jungle
- 0.025km/h if landmines

Use dxdy to calculate the distance from nearest waypoint to the destination.

Doing this last step in a separate function will have very little overhead
costs.

On Tue, Apr 19, 2016 at 8:39 PM, Steven M. Ottens <steven at minst.net> wrote:

> Hi all,
>
> I am working on a tool that will calculate the travel time from villages
> to for instance the nearest hospital for rural accessibility analysis. So
> far I have build a tool which will calculate this for 215.000 villages in a
> few minutes, thanks to the help of Daniel P. However I realized that not
> all villages are on a road, actually quite a few are at least an hour walk
> from the nearest drivable road see:
> http://stvno.github.io/img/OSRM-snapping.png
> The villages are typically connected to the roads by informal trails,
> which I do not have as a road network. So I was wondering if it would be
> possible to add a basic penalty to the distance of the point to the nearest
> I am aware that the nearest service will provide me with the distance:
> https://github.com/Project-OSRM/osrm-backend/wiki/New-Server-api#service-nearest
> but before I am going to calculate the extra traveltime for each village, I
> was wondering if it is possible to integrate this with an osrm.table
> request. I am aware this opens quite a can of worms: if there is a penalty
> to snapping, it might be worth it to snap to a road which is further away,
> but in the end quicker to get to the destination. But for the moment I'm
>
> Any suggestions on how to handle this?
>
> Steven
>
>
>
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>

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