The JMU/GPS Base Station is housed in the Geographic Science Program
at James Madison University, Harrisonburg, Va. 22807, (540) 568-6199.
Inquiries should be addressed to Dr. Jack Gentile (gentiljr@jmu.edu).
Station name:
JMU_Geography
Default file designation:
J
Location coordinates:
Lat. 38*26'02.08481" North
Lon. 78*51'44.72485" West
HAE = 420.195 m
The base station is set up to collect data from 1100 until 2300 UTC,
seven days a week. (If other times are desired contact the Geographic
Science Program).
To download base files from the Internet site, simply select the appropriate
files from the list and click the left mouse button. A screen will appear
that asks for the destination. It is suggested that the base files be
saved to the Base Folder in the appropriate Project Folder.
The standard file naming convention is used.
a. File Format
File format is:
JYYYYMMDDHH.exe
Where:
J = the station designation (JMU)
Y = the year (eg. 2004)
MM = the Month
DD = the day
HH = the hour (UTC)
.exe = indicates that the file is “zipped”, and will unzip
automatically when double clicked.
Example: A typical base station file might be J2004012015.exe This file
was created on Jan. 20, 2004 , at 10AM EST , and includes the data collected
from 10AM (1500 UTC) to 11AM (1600 UTC).
*Important* The system collects data using
UTC (Universal Time Coordinates). Therefore, local times must be converted
to UTC. The local time offset is negative five
(-5) hours during Eastern Standard Time (Nov. - April), and negative four
(-4) hours during Daylight Savings Time (April - Nov.). Also, the system
uses a 24-hour clock. For example: if you were collecting field data at
10AM EST, the concordant base file time would be 1500 (10:00 + 5:00 =
1500). See the UTC Time Conversion Table below.
b. UTC Time Conversion Table
The satellite clocks are set to UTC (Universal Time Coordinates), which
means that local times are set 4 or 5 hours behind the satellite clocks
depending on the time of year. The following table should help when determining
the appropriate base files required to match you field data.
*Important*: Although base files change
names at the hour every hour, rover files that cross hours do not change
names at the hour. A Rover file starting at 10am and ending at 11:29am
on Feb. 9, 1996 will be called R020915A.ssf. The necessary base files
to process this data include A1996020915.ssf, and A1996020916.ssf.
*Caution*When downloading base files that cross
midnight UTC, the date of the file also changes. You must be certain that
if you’re collecting data at 7pm EST or 8pm DST that you get the proper
base files. For example, a file collected for 4 hours beginning at 6pm
on October 15, 2004 (R101522A) would use the base files: J2004101522.ssf;
J2004101523.ssf; J2004101600.ssf; and J2004101601.ssf.
