Reading Ngs Datasheet

[+tnfishdaddy]

I have been geocaching and want to start finding some benchmarks. I found a link to the NGS datasheet by county. I went in and found my state and county and told it to search for benchmarks by gps. I figured I would start here before I started trying to find them with just the description. There is a lot of info that I can't decipher. First I can't find the gps coordinates. Then I got to looking at the descriptions and it would give me a number and then the letter m. Is this miles or meters? I just need help understanding all this info. By the way, anybody wanting to know what I am looking at, I plugged in TN and Greene County. Thanks.

[+rogbarn]

Welcome to the wonderful world of benchmark hunting!

 

To help you decipher datasheets better, I would suggest that you go to the Tell me more about DATASHEETS link on the main NGS datasheet page. From here the two best pages are under the heading FORMAT, "samples" with hyperlinks to explain some of the various sections and "specifications". There a lot of material in there. Be aware that some sections of the datasheet are not useful to the benchmark hunter but others can be very useful if you know what you are reading.

 

In particular and in reference to your questions:

1. The coordinates on the datasheet is about the 8th line down, starting with "* NAD". It provides coordinates in the format of DD MM SS.S or DD MM S.SSSSS. Longitude provides for a three digit for degrees. This can be entered manually into your GPS by changing the units of the GPS to DMS or by converting the DMS to the usual GPS default of DD MM.MMMM and then entering. Or, you can run the datasheets thru BMGPX to create a GPX file that can be loaded to your GPS automatically.

2. Many descriptions give meters first and the feet in parenthesizes. Meters is usually "m" or "M". If you give us a specific PID, we can read it and be a bit more sure about that generalization.

 

I hope this gives you a start to understanding the datasheet and encouragement to go out and find the benchmark. As you learn more and have more questions, feel free to post them here, there are a lot of amateurs and professionals that will be willing to provide answers.

 

edit for typos

Edited February 2, 2005 by rogbarn

[+5Wishes]

You can also view the GPX file by opening it in USAPhotoMaps. This is a cool piece of software that you can use to view the coordinates on both topo maps and aerial photos. Works great if your GPSr does not have built-in mapping capability. You can download it at www.jdmcox.com.

 

Also, if you want to use your GPS, look for marks that have ADJUSTED coordinates. SCALED coordinates are not as accurate and can be off by as much as 300' or more.

 

I hope you enjoy your first benchmark hunts. I find they are more enjoyable than caching, simply because you are looking for something that may or may not still be there after so many years.