PSN-L Email List Message

Subject: New SDR release, GPS without SA and new A/D card
From: "Larry Cochrane" cochrane@..............
Date: Sat, 16 Jun 2001 00:45:24 -0700

SDR Users,

I'm pleased to announce the new release of SDR and that SDR is now out of
beta! This evening I updated the documentation at with all of the new features and
changes to the software from the last release. This page also has links to
download the new version.

One of the things I just changed is higher precision to the latitude and
longitude numbers the user can enter for their sensor location. I just found
out a few days ago that SA, the stuff added to the GPS signal to make the
position less accurate, has been turned off over a year ago. I remember
hearing talk about it being turning off a few years ago, but I sure don't
remember hearing about it actually being turned off... Now that SA has been
turned off I did a site survey using one of my timing GPS systems and a
program called WinOncore by Motorola. This program will average the data
from a Oncore GPS receiver and display the data on the screen. With SA off,
and averaging the position data for 2 days, the accuracy should be under 1
meter. So that the user could enter this data I needed to change the SDR so
that the user could place more numbers past the decimal point. Before it was
limited to 3, now one can enter up to 6. With 6 numbers of precision the
user can enter a position accurate down to a few centimeters.

After 2 days of averaging the height information displayed by WinOncore
seemed a little strange. The number it came up with was -17.29 meters. As
far as I know Redwood City is above sea level. After doing some research on
the web I found that the height reported by WinOncore was GPS Height in WGS
84 ordinance, not local Mean Sea Level (MSL). To convert from GPS Height to
MSL I used a program called GEOID96
( After entering my location, it
came back with a number of -32.447 meters. I think this means I'm ~15 meters
(~49 feet) above local MSL. If I have done anything wrong here please let me
know. Also, I'm assuming that the seismology community uses local MSL for
sensor height. If this is not correct, please let me know....

This release now supports my new A/D board. As most of you know I had a
problem with getting 16 bit A/D chips from Burr-Brown (now owned by TI).
Since I wasn't sure I was ever going to get more chips I modified my board
for another 16 bit A/D chip made by several manufactures. Right after
getting the artwork back to make the new board I got the BB parts... If you
install SDR version 4.0 in a new directory and startup the program, you will
be asked for the A/D board rev number. At this point everyone has Rev 2

Also new with this release is support for a new field in the PSN Type 4
format. I added a Datalogger ID string in the variable header section of the
event file. See for more
information. Currently SDR places "SDR 4.0" in the field. The next release
of WinQuake will display this field in the Sensor Information dialog box.

If you use the new SDR version, and send in event files, please fill in the
new fields offered by the new PSN format. It's really nice to be able to see
what type of sensor is used to create the event file. The station operator
should enter a short description of the sensor in the "Sensor Information"
field for each channel. If you have a GPS receiver, and have not done a site
survey within the last year, please re check your sensor's position and
enter the more precise numbers in the new version of SDR. The next version
of WinQuake will display the higher precision numbers. The current version
only displays lat / long down to 3 numbers past the decimal point.

Larry Cochrane
Redwood City, PSN
Larry Cochrane


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Larry Cochrane <cochrane@..............>