Please use the NumberBox editor for your 'latitude' and 'longitude' fields.
<GridColumn field="latitude" title="Latitude" :editable="true" >
<template slot="edit" slot-scope="scope">
<NumberBox v-model="scope.row.latitude" :precision="2"></NumberBox>
</template>
</GridColumn>
<GridColumn field="longitude" title="Longitude" :editable="true" >
<template slot="edit" slot-scope="scope">
<NumberBox v-model="scope.row.longitude" :precision="2"></NumberBox>
</template>
</GridColumn>