I'm developing an application which uses PostGIS functions for measurements in the USA. In nutshell: the software is running in a car and use PostGIS functions in real time. For example: to measure distance of the nearest object (ST_Dwithin) and decide wheter the car is within a protected area or not (ST_Intersects). It is important that the function should be called at least 5 times in every seconds, so the running time is very important.
The input parameter of the function is the current GPS position, and returns with distance values (in meters). In addition to this: Important: I have to calculate the distance of the nearest objects within 0.4 mile.
I have polygon datasets that contain the special areas in WGS84 (EPSG:4326).
Now, I have to choose a suitable projection for this purpose (measurements of distances). The problem is that this software should be able to run in any sates within the USA (except for Alaska and the islands).
Is it possbile to use one CRS for this job or I have to split the polygons and use different projections in every states (this method would make a lot of difficulties)?
I don't want to use Geography data type because it is much slower than the geography.
What do you think, which CRS would be the best for this task?
I read many articles regaring this topic, but I'm still confused about the accuracy. I have to measure relatively short distances (maximum 0.4 mile).