Review isolines detalisation and smoothing settings #5567

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opened 2023-07-17 20:09:29 +00:00 by pastk · 0 comments

pastk commented

2023-07-17 20:09:29 +00:00

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The main purpose of isolines is to give information about altitude changes, hence their "vertical" aspect (step between lines or density) is more important than "horizontal" precision.

But current OM settings are rather opposite.
Do we need such "horizontal" detail? At the same time its impossible to say is it left or right side which is higher :) Because the "vertical step" between isolines is too big.
The first screenshot is with spline smoothing turned off - so that points density is more obvious (it looks quite high).
The second is the current situation.

The third screenshot above uses just 2 additional points for spline smoothing instead of current 4 - almost no change!
On the forth screen only 1 additional smoothing point is used - there are more sharp corners, but looks good overall - could be used in a battery saving mode perhaps.

Here is an example of how isolines will look after reducing simplificationZoom param from 15 (default for normal profile) to 14:

IMO not much information is lost in practical sense. But achieved space savings could be used to try increase isolines density.
(in this Macedonia case the mwm size reduced by 5.5%)

Related to #4580

The main purpose of isolines is to give information about altitude changes, hence their "vertical" aspect (step between lines or density) is more important than "horizontal" precision. But current OM settings are rather opposite. Do we need such "horizontal" detail? At the same time its impossible to say is it left or right side which is higher :) Because the "vertical step" between isolines is too big. The first screenshot is with spline smoothing turned off - so that points density is more obvious (it looks quite high). The second is the current situation. ![isolines-over-detalisation](https://github.com/organicmaps/organicmaps/assets/18434508/e43a7a16-de6d-4fc4-8ba0-68614fcd698f) The third screenshot above uses just 2 additional points for spline smoothing instead of current 4 - almost no change! On the forth screen only 1 additional smoothing point is used - there are more sharp corners, but looks good overall - could be used in a battery saving mode perhaps. Here is an example of how isolines will look after reducing `simplificationZoom` param from 15 (default for `normal` profile) to 14: ![isolines-reduced-1zl](https://github.com/organicmaps/organicmaps/assets/18434508/8a68cb15-7192-43ea-bf4d-8a2d4141ea00) IMO not much information is lost in practical sense. But achieved space savings could be used to try increase isolines density. (in this Macedonia case the mwm size reduced by 5.5%) Related to #4580

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