Description of monthly csv formatted files containing mobile observations aggregated into minute values on a .0005 latitude-longitude grid (~550 km).

The fundamental (draft) parameters defining the aggregated statistics in these files are:
    8 3-hour time intervals (0-3 MT, 3-6 MT, etc.)
    9,100 grid squares at 0.005 degree latitude/longitude (~550 m) resolution defining the core area in Salt Lake County covered by the bus routes
    Reports are provided here only if at least 11 observations were made in the 3-h block within that specific grid square 

The current reasoning for this file format is as follows:
    While data are recorded at 5 sec intervals on buses and 2 seconds on Trax, the core sensors (temp, PM, and O3) have time responses longer than that (order minute).
    SLC city blocks are typically 200 m in length. Hence, observations are aggregated within 1-2+ typical blocks route sections in each direction
    Buses and Trains travel at speeds up to 30 m/s but typically are moving along routes at speeds of 5-15 m/s and stopping frequently.

File name format and first row header
ebus_min_YYYY_MM.csv
times,LAT,LON,ELV,ROW,COL,GSP,SP,TT,TRH,PM1,PM2.5,PM4,PM10,PRHI,O3,PMF,O3F,GPF,SPF

trx_min_YYYY_MM.csv
times,LAT,LON,ELV,ROW,COL,SP,TT,TRH,PM2.5,PRHI,O3,PMF,O3F,GPF,SPF

Each row contains unique time and location information
All values are medians from 1-12 observations from buses, and 1-30 observations from TRAX concentrations.
Empty values indicate data not available

Variabes. 
    Time: YYYY-MM-DD HH:mm:00  
    LAT: Latitude 
    LON: Longitude
    ROW,COL: location in the Salt Lake Valley defined by index values within a 91x100 0.005 resolution lat-lon grid
    ROW is longitude and COL is latitude. Further Grid information included below
    GSP: Onboard GPS-derived vehicle speed (m/s) 
    SP: Vehicle speed derived from successive lat/lon locations (m/s) 
    TT: External air temperature (C) inside radiation shield on top of vehicle
    TRH: External relative humidity (%) inside radiation shield on top of vehicle
    PM1: PM2.5, PM4, PM10. Particulate concentrations of differing sizes (ug/m^3). 
         Particulate sensors installed vary over time. PM2.5 concentrations are typically available
    PRHI: RH inside particulate sensor. When external RH is high, particulate sensors 

    

Grid Information
    Corner coordinates of the grid are as follows:
    bot_left_lat  = 40.45
    bot_left_lon  = -112.20
    top_right_lat = 40.95
    top_right_lon = -111.75

Companion csv files provide the longitude and latitude for each of the 91x100 grid squares
    longitude_005.csv
    latitude_005.csv

Additional QC applied prior to aggregation
    A bus must report at least one of the following: Bus Top Temperature; O3, or PM2.5
    Bus top temperatures set to nan if BTT<-30C or BTT>50C
    Bus reports from outside the grid domain not processed

QA and Info Flags

    BGPF: Percentage of observations with Bus GPS Flag set to 1. 0%- there are no GPS flags set for any observations. 100%- every observation has GPS flag=1
        GPS flag reflects multiple possible conditions, including GPS location uncertainty and proximity to the bus depot. 
    BSPF: Percentage of observations with bus speed < 1 m/s. 0%- all speeds > 1 m/s. 100%- every observation has bus speed <1 m/sample
        BSPF is a single indicator of likelihood that the bus is enroute.However, the BSP percentiles provide more detail on the bus speed for that location/time interval
        Typically, the BSPF flag is more useful to detect stationary vehicles than the BGPF flag.
    O3F: Percentage of observations with O3 Flag set to 1. 0%- there are no O3 flags set for any observations. 100%- every observation has O3 flag=1
        O3 flag of 1 indicates likelihood of flow rate issue or high temperature  affecting measurements
    PMF: Percentage of observations with M Flag set to 1. 0%- there are no PM flags set for any observations. 100%- every observation has PM flag=1
        PM flag of 1 indicates likelihood of flow rate issue or high external RH (>80%) that may affect measurements

Variable Statistical Parameters (Variable suffixes)
    _CT: Count of observations for that grid square and time interval (11 is the minimum possible; a powered stationary vehicle may provide as many as 2160 observations in a 3h interval)
    _P01,_P10,_P25,_P50,_P75,_P90,_P99: Observation sample percentiles to define typical and extreme conditions

Variables
    BSP: Bus speed (m/s). Direction information is not provided since the correspinding statistical metrics would be difficult to interpret
    BTRH: Bus Top Relative Humidity (%). Exterior relative humidity. PM may read heigher than environment if BTRH high (> 80%)
    BTT: Bus Top Temperature (C). Exterior temperature in non-aspirated shield (may read higher than environment if bus not moving)
    O3: Ozone concentration (ppb). If sensor temperature excessively high, then concentrations may be exactly half that observed
    PM2.5: PM2.5 concentration (ug/m3). 
    PRHI: Relative humidity (%) interior to the sensor. When sensor detects RH > 35%, then heater turned on to attempt to maintain that RH. That often leads to
        PM2.5 concentration oscillations in moist environments as the heater cycles on/off to maintain that sensor RH