Fun test of GPSr accuracy-Adjusted Benchmarks

[+EScout]

Thanks to solohiker for his thread on Calibrating in Benchmarks I learned some new fun stuff about super accurate benchmarks (to the centimeter)

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A repeat of my post:

 

Thanks for the info on these adjusted benchmarks. Found one today and tested my Garmin Legend for Lat and Lon. Over the mark, the Garmin said it should be 10' SE and satellite page showed 15' "accuracy". With WAAS on, the Garmin said it should be 6' E with 8' "accuracy". (over 10 minutes for reading)

 

This mark, DY2499, is in a good open site, 165' elevation, near a steep cliff dropping to the ocean, with a good view of the sky and horizon.

 

Rig: Garmin Legend, firmware 2.50

Time: 11:30 AM Local, 16Mar03

WX: very clear and sunny after a storm blew through.

Sats: 8 received plus WAAS 47

Mark as listed: 33 44 29.32374N

118 24 05.66689W

Converted to Min: 33 44.488729N

118 24.094448W

Waypoint in Garmin: 33 44.489N

118 24.094W

 

The NGS lists the adjusted location of this mark to the one hundred thousandth of a second. The Garmin only allows one thousandth of a minute. A quick calculation shows the the rounded coords in the Garmin should have the waypoint about 2.8' NE of the benchmark instead of showing it to be 6'E. Yikes, even closer. I am surprised and pleased.

 

Go to this site for a list of Adjusted Benchmarks near you. http://www.ngs.noaa.gov/datasheet.html

 

At this site, NGS Data sheets: Retrieve Data Sheets>county(new)>state>get county>GPS sites only + your county.

Have fun.

[solohiker]

I am glad you could make use of the info. I got my info from an informed soul on the sci.geo.satellite-nav newsgroup. Can't remember who exactly.

 

After years of use, drops on rocks, drops into water and general knocking about it was nice to know that my old GPS was still giving reasonably accurate readings.