[mkgmap-dev] Is height: filter working as described?

Thu Feb 2 13:06:22 GMT 2017

Hi Carols,

some guessing on my part, hope someone corrects if I'm wrong.

As I understand, elevations in img are stored in feet.

Filters hight:m=>ft and conv:m=>ft indicate, that value from source has 
to be converted into feet, as expected by img format.

When you look at map, you see height units according to settings in GPS. 
You can set meters or feet. So for hight:m=>ft, these values are correct:
ele=500, map: ", 500 m" = 1650ft, default conversion
ele=500m, map: ", 500 m" = 1650ft, converted form meters
ele=500ft, map: ", 152 m" = 499ft, preserved feet

Settings in GPS are valid only for some objects types and label content. 
Conversion in GPS is done, when label starts with numeric or numeric is 
prefixed by special separator (it is [0x1f] for cgpsmapper). I guess 
filter "hight:" adds separator and GPS converts it to ", ".

Now filter hight:ft=>m seems to be kind of useless. It converts feet to 
meters, stores this value in img and adds a prefix, indicating that 
value is in feet. What we need here, is no conversion but separator 
only. Maybe something like this could work: {ele|height:ft=>ft}.

Actually it always should be feet as a destination for height, we could 
simplify this filter like this: {ele|height:m} or {ele|height:ft}, 
indicating only default unit in source data.

-- 
Best regards,
Andrzej