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Bm Vs Bz


skillett
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I am volunteering with the national map corps. My quad is copperas cove ,tx. There is a BM listed " BM1034" that is listed as being on the edge of town. and the data sheet for BZ1034 says it's forty miles north. I can find no reference for BM1034 Just BZ1034

In the description it says on the last recovery attempt by the USPS that the mark was not found. the data on my quad is pretty old. Has the usgs changed the the designation of BM's from BM to BZ?. the benchmarks that I have done so far were right where they were supposed to be. But, they are listed in the datasheets as BZ not BM When I plug the lat/lon into my mapping program it is close to where the datasheet says it is. Should I try to correct this through the usgs or not? The usgs NMC project is only interested in gps data for certain structures and not benchmarks.

skillett :P

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Skillet.

 

As you may know A USGS Map only includes USGS Survey, But some of their survey markers did make it into the NGS Database. Keep in mind though that they (NGS and USGS) are separate and different US Government Agencies with different missions.

 

When you see BM1034 on a map, USGS Surveyors leveled an elevation of 1034 feet at that location, as based on the datum that was in use at the time. What does BM Mean? Bench Mark. By definition; a point of measured elevation.

 

When you see a BZ1034 on an NGS Datasheet, you are seeing a computer generated naming convention which becomes a File name for data in a database. The Data is not the PID.

 

In this case the BZ area of the country happens to be where you live. Many of the NGS stations in your local area will have BZ in their Data Name, PID.

 

In reality we have o the one hand a Terminology and on the other a file naming convention. There is more about all this in the FAQ, I am sure you already read that though :-D

 

Rob

Edited by evenfall
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thanks for the info. But. How can I use the quad to retrieve data from the NGS database. I went and tried this morning and could not find the datasheet for a BM that I have found near my house. (I got the sheet from here) it is BM1071 on the map. I must have been doing somthing wrong in thinking I had the data sheets for the benchmark on the quad. BM1071 is not listed in the ngs database under that name. HELP!!

skillett :P

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To stress what evenfall and others wrote earlier....

 

If you see "BM1071" printed on a USGS topo map, it means there is a bench mark located at that spot (usually marked by an X), and the elevation is 1071 feet. The PID (permanent identification number), which is also in the format AA1234 -- two letters followed by a four-digit number -- is never printed on the USGS map.

 

This will be a little clearer to you, I think, if you study the FAQ, but in short, each benchmark in the NGS database is assigned both a PID and a name ("designation"), which might be JONES or N 105 or almost anything else.

 

Certain benchmarks are called triangulation stations because of the way they were measured in the pre-GPS era, and these are represented on USGS topo maps as a triangle, and the designation is usually printed alongside.

 

Many, probably a majority, of benchmarks appearing on USGS topo maps are not in the NGS or Geocaching database.

 

If you go to this page and enter the name of your quad, you will get a list of all the NGS-listed marks on this sheet. Here's the list I got:

 

|Dist|PID...|H V|Vert_Source|Approx.|Approx..|Stab|Designation

|----|------|- -|-----------|-------|--------|----|-----------

|....|BZ0973|. 1|88/ADJUSTED|N310729|W0975403|D...|B 84

|....|BZ0974|. 1|88/ADJUSTED|N310722|W0975351|C...|C 84

|....|BZ1349|3 .|...........|N310722|W0975357|....|COPPERAS COVE CHURCH SPIRE

|....|BZ1350|3 .|...........|N310718|W0975357|....|COPPERAS COVE SCHOOLHOUSE DOME

|....|BZ1220|. 1|88/ADJUSTED|N310502|W0975823|A...|D 1475

|....|BZ1351|1 3|29/LEVELING|N310657|W0975601|....|GILMORE RESET

|....|BZ1219|. 1|88/ADJUSTED|N310445|W0975926|B...|H 1475

|....|BZ1221|. 1|88/ADJUSTED|N310528|W0975734|D...|J 1475

|....|BZ1222|. 1|88/ADJUSTED|N310546|W0975630|D...|K 1475

|....|BZ1223|. 1|88/ADJUSTED|N310614|W0975519|B...|L 1475

|....|BZ1224|. 1|88/ADJUSTED|N310650|W0975423|D...|M 1475

|....|BZ0972|. 1|88/ADJUSTED|N310719|W0975340|C...|S 4

|....|BZ1217|. p|88/POSTED..|N310515|W0975922|....|T 4

|....|AC7307|3 .|29/VERT ANG|N310456|W0975755|....|TAYLOR

|....|BZ0971|. 1|88/ADJUSTED|N310719|W0975246|D...|X 49

|....|BZ0979|. 1|88/ADJUSTED|N310613|W0975822|C...|Y 83

 

Most of us who have been at this for a while find it's much more productive to go out looking for benchmarks that are in the NGS/Geocaching database, rather than finding a metal disk, for example, and then seeing if it's in the database.

 

Hope this helps.

 

-ArtMan-

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Here's a link to a prior discussion about the USGS benchmarks. There are a large number of them, especially off the beaten path. The crux of the matter is in the middle of what evenfall said:

 

Many, probably a majority, of benchmarks appearing on USGS topo maps are not in the NGS or Geocaching database.

 

It's not in the database, and you'll have to look for it with just the X to guide you. Or, you could contact the USGS from above and get a paper copy of all of the data for your area.

 

It's bad luck that you live in an area of the country where the PID designation is somewhat confusing with the topographic BM markers. Imagine living in Burleson county, TX, altitude 290 ft. or so, where you're looking for stations like BM0225 A 208

Edited by BuckBrooke
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Here's a link to a prior discussion about the USGS benchmarks.  There are a large number of them, especially off the beaten path.  The crux of the matter is in the middle of what evenfall said:

 

Many, probably a majority, of benchmarks appearing on USGS topo maps are not in the NGS or Geocaching database.

 

It's not in the database, and you'll have to look for it with just the X to guide you. Or, you could contact the USGS from above and get a paper copy of all of the data for your area.

 

It's bad luck that you live in an area of the country where the PID designation is somewhat confusing with the topographic BM markers. Imagine living in Burleson county, TX, altitude 290 ft. or so, where you're looking for stations like BM0225 A 208

So if I find one that's not in the database should I try to do an update to the ngs database per a previous disscussion here? there are some Bm's on my quad that are not in the database. some are out in the boonies. I guess I will have to do some studying to figure out how to get LAT/LON coords down to the second off the quad to pinpoint the location. BTW there is a degree confluence point in the SW corner of my quad. 31.00N 98.00W I plan on visiting it too. It has already been found But woulld still be cool.

thanks again guys for all the help.

skillett :o

Edited by skillett
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skillett,

It's not feasible to get a few USGS marks to be included into the NGS database. It's a long, arduous process from what I hear, and they only accept points with incredibly precise surveying accuracy. The BM marks on your map, marked with Xs, most likely were placed during one of the surveying activity pulses in the 1940s through 1960s. They may or may not be accurate enough. Nonetheless, it's a USGS point and they won't send it to be added to NGS anytime soon.

 

Good luck with the map updating and the confluence hunting. A few folks in this forum enjoy the challenge of finding the USGS marks with just an X on a map to guide them.

Edited by BuckBrooke
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skillett -

 

It is not up to us to update the NGS database with survey disks that are not included in the NGS database. They do not want us to be trying to do that. In fact, they don't want us to try to communicate anything at all with them about survey disks that are not in their database.

 

We have no place to log these disks on either the Geocaching website or the NGS website.

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skillet:

 

I'm also a mapping corp volunteer for USGS. I'm sorry to say, forget the "BMxxxx" on the USGS topo's for now. Neither NGS nor USGS wants or needs us to do anything with them AT THE MOMENT. Of course, that might chhange in the future. I have found some, and other than the "COOL!" reaction you can get, the only thing that is interesting about them is the elevation. Put your GPS receiver on one, and you will see how inaccurate your it is in elevation (technical note: assuming the vertical datums were anywhere near similar....).

 

Technical discussion starter: Anyone have an idea how accurate in Horizontal position and Vertical elevation these USGS Bench Marks are? Were they done as rigorously as a true NGS Bench Mark? Worse than third order?

 

Klemmer

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skillett -

 

It is not up to us to update the NGS database with survey disks that are not included in the NGS database.  They do not want us to be trying to do that.  In fact, they don't want us to try to communicate anything at all with them about survey disks that are not in their database.

 

We have no place to log these disks on either the Geocaching website or the NGS website.

floolw this link to a post discussing updating datasheet info

http://forums.Groundspeak.com/GC/index.php?showtopic=80447

Unless i am reading it wrong. the ngs is activly seeking updated info from us.

skillett. :Dex.php?

Edited by skillett
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