[OSM-dev] Which is best for this task, osmosis, osmconvert osmupdate or...

[Dave F.]

Hi

I'm a bit unsure which program is best to perform the actions I list below.

I've previously download a file of all OSM data within a rectangular 
area. I then use mkgmap to convert it to the format by my Garmin GPSr. 
In the future I'd like to change that so it's a multi faceted polygon of 
only specified OSM entities.

At present, each time I want to update the file, I'm downloading every 
entity, even if they haven't been amended. What I need is to download 
any changes within the polygon since I last updated. I read about 
minute, hourly & daily diffs. Am I able to state the date I last updated 
as the start point for new data?

There appear to be a few programs able to do what I require, but unsure 
which is best suited. Is Osmosis a bit overblown for my purpose. 
Osmupdate seems a bit more lightweight. Osmconvert appears to discourage 
doing what I need: 
http://wiki.openstreetmap.org/wiki/Osmupdate#Use_Cases. Overpass also 
has a way to download diffs. Anyone used that?

Is it better to work with a raw OSM data file or use a .pbf file? In 
fact I'm a bit confused what one is. From the wiki it firstly says 
"alternative to the XML format", but then goes on to compare it with a 
compressed file format. Which is it?

Your help is appreciated.

Cheers
Dave F.

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