Exporting to JSON using mongoexport any record that contains a float which has value NaN will fail.

Simple Example:

{
"slatlng" : [NaN, NaN]
}

Additionally:

When in the mongo console, you can exclude such records using:

"slatlng" : {$ne [NaN, NaN]}

but mongoexport cannot parse this as a valid json query. So you cannot do it.