ETL 1110-1-184
01 Oct 1998
{SSSS}{DDD}0.{YY}{T}.
The letters and hour time blocks are
related by:
start hour: 0000 0100 0200 0300 ...
2100 2200 2300
letter:
a
b
c
d
...
v
w
x
The file types are as follows:
File type
Ending(T)
Description
Meteorological
m
Observation
o
Carrier Phase observations
Navigation
n
Ephemeris Data
Summary
s
Message File
c. Sample Rate or Epoch Interval. The data is collected,
for a majority of the sites, at a 30-second epoch interval. A
few sites are collected at a 5-second epoch interval. The Readme
file on the CORS homepage contains a list of which sites are
logging data at 5 or 30 second epoch interval. When using a CORS
site for a project, make sure all data or sample rates of the
user's GPS receivers are set the same.
(1) For code phase positioning where a 30-second epoch
interval is too slow, it is possible to interpolate observational
data at faster rates using NGS's INTERPO program. INTERPO will
take a standard RINEX-format file as input and generates another
RINEX-format file with interpolated GPS satellite observations at
a user-specified rate of 25,20,15,10,5 or 1 second. If planning
to use interpolated data, the user or rover's GPS receiver should
be collecting data at the desired data rate. INTERPO should not
be used on GPS data collected by the user.
(2) For carrier phase positioning, INTERPO should not be
used. Users may encounter significant problems in use of
interpolated carrier phase data.
B-4. Data Availability.
a. On-Line Data. For each CORS site, RINEX 2 data is
available over the Internet for a 31-day period. The data can be
downloaded off the CORS homepage.
b. Archived Data. Archived data (data collected before the
31-day on-line period) can be obtained from NGS through a special
request. However, this request is limited to no more than 15 days
of data for one station per request or equivalent space for
several sites. Beyond this amount, NGS may charge a fee for
processing the request. Data requested is made available for 7
days.
B-3
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