modifying paramter in gmapping launch

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hi what is the parameter that stand of changing the update time of the map and the update range of the map and every values is stand for what exactly I read gmapping few time and try to change lstep & astep cuse my odometery is too small but nothing change and if increase my odometery in a gain of 1000 it start to appear in the map but the update of the map will late I want know what I really need to modify in launch file to decrease the transition to be Compatible with my odom and how to decrease the update time of the map. and I need to know what is this exactly do:

1. ogain
2. linearUpdate
3. angularUpdate
4. llsamplerange

thanks for help.