Kind of found my First

[+Woodstramp]

http://www.geocaching.com/mark/details.aspx?PID=DH0212

 

I'm new to GPS and have tried several times to find listed geocaches. I've yet to find one, so I thought I'd try to find a benchmark to check if my Explorist 400 is accurate enough for GCing. Benchmarks being something more concrete, that is. I figured that finding that spot would be easier than finding a cammoed 35 mm film can.

 

Above is the URL for a benchmark I tried to locate this afternoon. It is local and I know where the school in the background is.

 

My Magellan's compass but me right near the culvert in the photo. From 200 feet the compass pointed right to the culvert. Standing exactly from where the bottom pic was taken (in the culvert ditch) my GPS was telling me that I was off about 50 feet. I never saw the benchmark disc. I think it's covered by grass/road dirt again. Judging from the other guy's notes and pics the disc is above the culvert pipe embedded in the concrete. I know that my Magellan doesn't have WAAS and that is a handicap, but is 50 feet decent accuracy for Geocaching?

 

Is 50 feet "close" compared to veteran cacher's standards?

[2oldfarts (the rockhounders)]

The benchmark that you used to check the accuracy of your GPSr only had scaled location coordinates. Those are normally off by 100 feet or more.

 

Try using THIS benchmark that has been previously found and has adjusted location coordinates. Your GPSr should put you within 10 feet of the actual mark.

 

For finding caches any GPSr that gets you within 25 to 30 of the cache is good. Some cachers don't do a very good job of getting accurate coordinates for their caches, so you still need to look for the most likely hiding places when caching. For benchmarks with scaled coordinates it is necessary to follow the written description to find the benchmark.

 

Good luck.

 

John

[+PFF]

Hi, Woodstramp,

 

As John mentioned, you unknowingly selected a poor target for checking your GPS receiver. If you look near the top of the data sheet, you will notice that the horizontal coordinates are SCALED. This means they are estimated from a map.

 

Not only does this make the mark difficult to find, but it would not have served your purpose, even if you'd spotted it. Benchmarks with SCALED coordinates can be up to 600 feet away from their published location--although most are within 50 to 100 feet. Oddly, you live in an area which is populated heavily with SCALED coordinate benchmarks.

 

I recommend going about 3.5 miles and trying to find AA2051. This mark has been found previously by one of our participants, and the horizontal coordinates are ADJUSTED. (Think: ADJUSTED = Accurate and SCALED = Somewhere.)

 

Again, this information applies only the ability of your GPSr to lead you to a precise point (as in searching for a cache). The same SCALED/ADJUSTED designations also apply to the elevation of the benchmark. However, don't waste your time trying to calibrate this feature of your receiver. While the Latitude and Longitude can accurate within a few feet, the elevation accuracy varies significantly from day to day, due to limitations in the GPS network.

 

By the way, you were on the "right track". Searching for a benchmark is an ideal way to check, and practice with, a GPS receiver. Give it another try, now that you know which ones to use. But be forewarned. Benchmark hunting can be addictive as geocaching!

 

-Paul-

[Wintertime]

My Magellan's compass but me right near the culvert in the photo. From 200 feet the compass pointed right to the culvert. Standing exactly from where the bottom pic was taken (in the culvert ditch) my GPS was telling me that I was off about 50 feet. I never saw the benchmark disc. I think it's covered by grass/road dirt again. Judging from the other guy's notes and pics the disc is above the culvert pipe embedded in the concrete. I know that my Magellan doesn't have WAAS and that is a handicap, but is 50 feet decent accuracy for Geocaching?

Were you using the coordinates at the top of the Geocaching.com page for that mark, or the ones that "Maconart" supplied? If the former, notice this text right below them: "Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)." If you click on the "more info" link, you'll be taken to the bottom of the page, where it explains that the location may be off by +/- 6 seconds of a degree, which is about 600 feet.

 

If, however, you were using Maconart's coordinates, then I would have expected your GPS to get you closer than 50 feet.

 

The two sets of coordinates appear, at rough estimate, to be about 100 feet apart.

 

Patty

[+PFF]

Confidential to Patty and John:

 

 

Obviously, three members of this forum need to get a life, which would include turning off the computer and going to to bed!

 

 

-Paul-

 

Sunday, 2:50 AM (Eastern Time)

[Wintertime]

Confidential to Patty and John:

 

Obviously, three members of this forum need to get a life, which would include turning off the computer and going to to bed!

 

Sunday, 2:50 AM (Eastern Time)

Hey, at least I'm in California, and isn't John in Arizona? So it wasn't all that late for us. (Although it appears that Groundspeak's timestamps are still on Standard time, if you were really posting at 2:50 EDT. So maybe it was 11:50 here; I don't remember now.) When I finished writing my posting and saw one from you, I was wondering what the heck someone in the East was doing up so late!

 

Patty

[+Black Dog Trackers]

Woodstramp -

 

I also recommend finding the marks that 2oldfarts (the rockhounders) and PFF have pointed out. Those marks are probably within an inch of the exact coordinates, a location much more accurate than our GPS receivers can determine. By the way, benchmark hunting often involves a bit of digging or moving dirt around a bit. If you do find a mark with Adjusted coordintes, set your GPS receiver to "go to" the listed coordinates, put your GPS reciever above or on top of it, and watch how far it says you are in feet from the coordintes for a while. That way, you will get an idea of how accurate your GPS receiver is. You should see it say stuff like 4 feet, 7 feet, 3 feet, etc., as if you were walking around in circles near the mark. If you want to get more serious, take data on the distances and azimuths from the stated coordinates that you read while the GPS receiver is above the mark.

[+Woodstramp]

The benchmark that you used to check the accuracy of your GPSr only had scaled location coordinates. Those are normally off by 100 feet or more.

 

Try using THIS benchmark that has been previously found and has adjusted location coordinates. Your GPSr should put you within 10 feet of the actual mark.

 

For finding caches any GPSr that gets you within 25 to 30 of the cache is good. Some cachers don't do a very good job of getting accurate coordinates for their caches, so you still need to look for the most likely hiding places when caching. For benchmarks with scaled coordinates it is necessary to follow the written description to find the benchmark.

 

Good luck.

 

John

 

Thanks. I'm still learning the lingo and ropes to all this stuff. I made note of the BM you listed and will give that one a try.

[+Woodstramp]

Hi, Woodstramp,

 

As John mentioned, you unknowingly selected a poor target for checking your GPS receiver. If you look near the top of the data sheet, you will notice that the horizontal coordinates are SCALED. This means they are estimated from a map.

 

Not only does this make the mark difficult to find, but it would not have served your purpose, even if you'd spotted it. Benchmarks with SCALED coordinates can be up to 600 feet away from their published location--although most are within 50 to 100 feet. Oddly, you live in an area which is populated heavily with SCALED coordinate benchmarks.

 

I recommend going about 3.5 miles and trying to find AA2051. This mark has been found previously by one of our participants, and the horizontal coordinates are ADJUSTED. (Think: ADJUSTED = Accurate and SCALED = Somewhere.)

 

Again, this information applies only the ability of your GPSr to lead you to a precise point (as in searching for a cache). The same SCALED/ADJUSTED designations also apply to the elevation of the benchmark. However, don't waste your time trying to calibrate this feature of your receiver. While the Latitude and Longitude can accurate within a few feet, the elevation accuracy varies significantly from day to day, due to limitations in the GPS network.

 

By the way, you were on the "right track". Searching for a benchmark is an ideal way to check, and practice with, a GPS receiver. Give it another try, now that you know which ones to use. But be forewarned. Benchmark hunting can be addictive as geocaching!

 

-Paul-

 

Got the one you listed and I'll add it to the list. It's not too far from my brother's place. Thanks.

[+Woodstramp]

Were you using the coordinates at the top of the Geocaching.com page for that mark, or the ones that "Maconart" supplied? If the former, notice this text right below them: "Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)." If you click on the "more info" link, you'll be taken to the bottom of the page, where it explains that the location may be off by +/- 6 seconds of a degree, which is about 600 feet.

 

If, however, you were using Maconart's coordinates, then I would have expected your GPS to get you closer than 50 feet.

 

The two sets of coordinates appear, at rough estimate, to be about 100 feet apart.

 

Patty

 

I just assumed that all the BM's listed were all dead on. I'd read the "adjusted" stuff and thought the surveyors had fixed it or something. Didn't even notice that Maconart had listed additional coordinates. I added his readings to the notes on that BM in my GPS. Thanks for pointing that out. Will hit that one again with the new coordinates.

[+Woodstramp]

Woodstramp -

 

I also recommend finding the marks that 2oldfarts (the rockhounders) and PFF have pointed out. Those marks are probably within an inch of the exact coordinates, a location much more accurate than our GPS receivers can determine. By the way, benchmark hunting often involves a bit of digging or moving dirt around a bit. If you do find a mark with Adjusted coordintes, set your GPS receiver to "go to" the listed coordinates, put your GPS reciever above or on top of it, and watch how far it says you are in feet from the coordintes for a while. That way, you will get an idea of how accurate your GPS receiver is. You should see it say stuff like 4 feet, 7 feet, 3 feet, etc., as if you were walking around in circles near the mark. If you want to get more serious, take data on the distances and azimuths from the stated coordinates that you read while the GPS receiver is above the mark.

 

Thanks for the pointers. I figured, with Maconart's note, that it may be covered again. It is right next to a road. it was grown over again. Sounds like time for purchasing a mini shovel.

[+Black Dog Trackers]

Woodstramp -

 

If you really want to check your GPSr, I would not use Maconart's note. I have no doubt that Maconart's coordinates are what was measured on the proper benchmark, but imagine that those coordinates are 7 feet NW of where the mark really is. Then you come along and your GPSr says the mark is 5 feet SW of where the mark really is and even farther from Maconart's coordinates.

 

Instead, just forget the scaled mark and someone else's measured coordinates for it, and just use a mark with adjusted coordintates to check your GPSr.

[+Black Dog Trackers]

By the way, the FAQ page has a pretty good list of benchmark hunting items to consider bringing on benchmark hunting trips. A probe is a main item to use, since ususally benchmarks are only hidden by a half inch or so of soil.

[Wintertime]

If you really want to check your GPSr, I would not use Maconart's note.

Oh, definitely. I mentioned "Maconart"'s coordinates only as a help in finding that specific benchmark. To check the accuracy of his GPSr, "Woodstamp" would definitely want to look for a benchmark that has adjusted horizontal coordinates.

 

Patty

[+Woodstramp]

The benchmark that you used to check the accuracy of your GPSr only had scaled location coordinates. Those are normally off by 100 feet or more.

 

Try using THIS benchmark that has been previously found and has adjusted location coordinates. Your GPSr should put you within 10 feet of the actual mark.

 

For finding caches any GPSr that gets you within 25 to 30 of the cache is good. Some cachers don't do a very good job of getting accurate coordinates for their caches, so you still need to look for the most likely hiding places when caching. For benchmarks with scaled coordinates it is necessary to follow the written description to find the benchmark.

 

Good luck.

 

John

 

Rockhounders,

 

FOUND the benchmark you posted this afternoon! It was easy to find and very accessible.....drove my PU right to it. It was some kind of fence post stake with red tape tied on. It also had survey writing on it.

 

My Explorist, when laid at the stake's base, said I was within only 8' away. Also got a waypoint there to compare with the one you linked to.

 

The original coordinates: N 33° 35.645 W 086° 21.674

 

Mine taken at the stake: N 33° 35.647 W 086° 21.675

 

Well, that's way more accurate than I would've ever thought.

 

Thank you.

[+Black Dog Trackers]

Woodstramp -

 

Well the actual marker is 3.3 feet from that stake.

[+Woodstramp]

If you really want to check your GPSr, I would not use Maconart's note.

Oh, definitely. I mentioned "Maconart"'s coordinates only as a help in finding that specific benchmark. To check the accuracy of his GPSr, "Woodstamp" would definitely want to look for a benchmark that has adjusted horizontal coordinates.

 

Patty

 

As mentioned to the Rockhounders above, I found that marker. I hit the one by the school right thereafter using Maconart's logged coordinates instead of the originals. His/her coordinates said I was only 14 feet away. That's a lot closer than the original one with 50'. Thanks. This is kind of cool.

[+Harry Dolphin]

Thanks for the pointers. I figured, with Maconart's note, that it may be covered again. It is right next to a road. it was grown over again. Sounds like time for purchasing a mini shovel.

 

Depending on the landscaping or local conditions, there is generally a hole of some sort left by the previous finder. I found one with a typo in the coords that was about a quarter mile off. The worst I've found with scaled coords was about a thousand feet off. This station does seem to show on the topo map, as being to the west and a smidge north of the published coords.

Description is a better way to find these (if still appropriate). Look for the concrete culvert (if it's still there.)

[+PFF]

Woodstamp wrote:

 

"This is kind of cool."

 

 

 

See.....I told you this is addictive!

 

 

Congratulations on your first benchmark finds!

 

 

-Paul-

[2oldfarts (the rockhounders)]

 

Rockhounders,

 

FOUND the benchmark you posted this afternoon! It was easy to find and very accessible.....drove my PU right to it. It was some kind of fence post stake with red tape tied on. It also had survey writing on it.

 

My Explorist, when laid at the stake's base, said I was within only 8' away. Also got a waypoint there to compare with the one you linked to.

 

The original coordinates: N 33° 35.645 W 086° 21.674

 

Mine taken at the stake: N 33° 35.647 W 086° 21.675

 

Well, that's way more accurate than I would've ever thought.

 

Thank you.

 

Congratulations on the find.

 

Of course, along with the good news about how accurate your GPSr is, comes the bad news! If you don't find a cache, you can't blame the GPSr......

 

Welcome to benchmark hunting.

 

John

[Wintertime]

FOUND the benchmark you posted this afternoon! It was easy to find and very accessible.....drove my PU right to it. It was some kind of fence post stake with red tape tied on. It also had survey writing on it.

That stake is called a "witness post." Did it look like one of the items on this page? According to the description on the mark's data sheet, the witness post is made of carsonite, so it should look like one of those in column three on that page.

 

Were you able to find the actual survey mark, or was it buried? As BDT noted, the mark is 3.3 feet from that stake. (South, according to the description.) So if it is buried, try probing gently with a long screwdriver and you'll probably find it easily!

 

Patty

[2oldfarts (the rockhounders)]

 

 

[+Woodstramp]

 

That stake is called a "witness post." Did it look like one of the items on this page? According to the description on the mark's data sheet, the witness post is made of carsonite, so it should look like one of those in column three on that page.

 

Were you able to find the actual survey mark, or was it buried? As BDT noted, the mark is 3.3 feet from that stake. (South, according to the description.) So if it is buried, try probing gently with a long screwdriver and you'll probably find it easily!

 

Patty

 

So you guys are now telling me that I didn't really have a success........I found a post and not the actual marker? I thought the post was the marker. Talkin' about snatching defeat from the jaws of victory....

 

It was what you call a witness post. Even had that written on it.

 

(South, according to the description.)

 

I was standing on it, apparently.

 

To think the real bandit was 1" of dirt and 1/2" of rubber sole away......

[+Black Dog Trackers]

Woodstramp -

 

I suggest going back with a probe like a stiff wire a few inches in length. A coathanger wire would probably not be stiff enough. Like Wintertime says, a very thin and long screwdriver (like some electornics technicians have) would be pretty ideal. Also some types fence wire is good too, if you see any place where people have been installing a 'cyclone fence' and leaving a few inches of it around (don't use the VERY soft aluminum stuff!).

 

You'll be probing for something big - the disk is about 3" in diameter but it would be in the center of a cement area about a foot in diameter.

 

The datasheet's verbal description includes this statement:

3.3 FT (1.0 M) SOUTH OF A CARSONITE WITNESS POST

So, you will need at least a cheap compass if your GPS receiver doesn't have a compass function (mine doesn't), so that you can find out which way is South from the carsonite witness post, and then measure 3.3 feet. You might have to clear away a bit of leaves and stuff, but probably not much dirt, by the looks of it.

Edited March 17, 2008 by Black Dog Trackers

[+Harry Dolphin]

Even with the compass on my GPS, I still carry a cheap compass! (I get them out of BrianSnat's caches. )

[+Woodstramp]

Black Dog,

 

I will take a probe of some kind next time. If the marker was 3 feet away to the south then I must have been standing on it.

 

Anyway, what's cool is I found my first benchmark yesterday and found my first geocache today.