Increment values in a string

I have a file with many lines of the form:

<trkpt lon="174.92797852" lat="-41.24854279">

I'm looking for a way to create a script to increment each lon value by a common factor and each lan value by another common factor, ie add .00022 to the lon value and .00044 to the lat value.

I thought I might be able to do this with sed but my limited knowledge fails me