Can I get some advice?

[+secondgunman]

First a little background.

 

I've been looking for FH0806 for a few months now and it's driving me crazy. You'll notice the location in the datasheet is scaled and the description isn't a lot to go on: "...THE MARK IS A DISK SET IN AN OUTCROP OF BEDROCK AT THE EDGE OF THE ARKANSAS RIVER, 108.20 METERS (355.0 FT) SOUTHWEST OF A LARGE METAL POLE AT THE OLD FORT SITE. THE MARK IS 1.22 METERS NNE FROM A WITNESS POST..."

 

For starters, there's no large metal pole, there's a large wooden flagpole that's in a location that makes perfect sense in context. You can see it in the sat view from Google at 35.387694,-94.432541 (this agrees with my GPSr to four decimal places by the way). Let's assume that this is what is referenced in the description and start from there.

 

The description gives a distance SOUTHWEST of the pole. I plugged this distance and a bearing of 225 degrees into FORWARD to get an approximate location of 35.387011, -94.433772. I understand that this bearing may be off by as much as +/- 30 degrees, but I thought it might at least narrow down my search a bit. My location and the scaled location from the datasheet were about 50 feet apart. Given the 2003 find on geocaching, I think I'm in about the right area. Obviously, there's no witness post or we wouldn't be having this discussion. The area around my calculated location is all bedrock, though as you move east you start going uphill quickly. The bedrock in many areas is covered by up to 8-10 inches of dirt that has eroded down the hillside.

 

I should also mention that NOAA's Geophysical Data Center shows a magnetic declination of 2° 28' E changing by 0° 7' W/year at the coordinates of the flagpole in the description.

 

I guess my questions are these:

 

1) When this mark was set in 1984, they listed a distance and general compass direction to the mark. Am I correct in assuming that "southwest" in the description is simply a general direction from the compass and not actually intended to mean 225 degrees?

 

2) They listed the distance as 108.20 meters. In my world, listing the last zero in that number means that it is a significant value and that it was measured to two decimal places of accuracy. I realize I'm splitting hairs at this distance and the difference between 108.1 and 108.3 is not huge, but was it really measured that accurately?

 

3) Because of the difference in altitude of the base of the flagpole and the location of the marker (6.10m according to the datasheet), how is that distance measured? Picturing a right triangle with the short leg going up from the mark, and the long leg going from a point in space above the mark to the base of the flagpole, what is being measured? Is the measurement for the long leg (the base) of the triangle or is it for they hypotenuse? I realize the difference is only ~0.2m, but I'm curious.

 

4) For marks like this with fairly sparse descriptions, is there an easier way than to trace out an arc at the correct distance and sweep with a metal detector (which I don't have). On a related note, is there an easier way to trace out that arc than with a tape measure? Because of the distance involved, the trees in the way, and the 6m elevation change, that's not the easiest thing to trace.

 

5) I'm still fairly new at this. Is there something in the datasheet that I've overlooked that would make this easier?

 

I hope those questions make sense. I'd welcome any input you good folks have on this.

[southpawaz]

 

I guess my questions are these:

 

1) When this mark was set in 1984, they listed a distance and general compass direction to the mark. Am I correct in assuming that "southwest" in the description is simply a general direction from the compass and not actually intended to mean 225 degrees?

 

Correct. If the direction was measured more accurately, they would likely have given an azimuth or bearing in degrees.

 

2) They listed the distance as 108.20 meters. In my world, listing the last zero in that number means that it is a significant value and that it was measured to two decimal places of accuracy. I realize I'm splitting hairs at this distance and the difference between 108.1 and 108.3 is not huge, but was it really measured that accurately?

 

In 1984 when this was set, the party may well have had available a total station instrument or other electronic distance measurement equipment that certainly would have allowed them to measure that distance very accurately.

 

3) Because of the difference in altitude of the base of the flagpole and the location of the marker (6.10m according to the datasheet), how is that distance measured? Picturing a right triangle with the short leg going up from the mark, and the long leg going from a point in space above the mark to the base of the flagpole, what is being measured? Is the measurement for the long leg (the base) of the triangle or is it for they hypotenuse? I realize the difference is only ~0.2m, but I'm curious.

 

Distances noted are generally measured horizontally. Use of a total station would convert a measured slope distance (the hypotenuse of your triangle) to the horizontal (the long leg of your triangle), as it would read the angle between those two sides when the distance was measured.

 

4) For marks like this with fairly sparse descriptions, is there an easier way than to trace out an arc at the correct distance and sweep with a metal detector (which I don't have). On a related note, is there an easier way to trace out that arc than with a tape measure? Because of the distance involved, the trees in the way, and the 6m elevation change, that's not the easiest thing to trace.

 

This one is made a bit tougher by the length of the referenced distance, but you're on the right track.

 

5) I'm still fairly new at this. Is there something in the datasheet that I've overlooked that would make this easier?

 

My quick look didn't reveal anything glaring. "At the edge of the Arkansas River" would be a key for me, as would the 50 foot estimate of the variance in coordinates noted in the geocaching log. It looks like the mark is shown on the Topo map for the area, you might see about trying to scale coordinates off of that, but 50 feet is pretty close as far as these go.

 

I hope those questions make sense. I'd welcome any input you good folks have on this.

 

Good luck, hope you find it and let us know if when you do.

[Bill93]

1) General compass direction

 

2) In 1984 this could have been done accurately with an electronic distance measurement device (EDM, possibly outboard of any theodolite) such as is now built into all modern surveyors' total station instruments. However the fact that the distance is 355.0 feet makes me wonder if it was to the nearest tenth or two of a foot and extra digits put on in the metric conversion.

 

3) All surveying distances are supposed to be horizontal distance unless labeled as a slope distance (hypotenuse). In 1984 an EDM would have read out the slope distance and they would have used the angle to compute horizontal distance. Now that is all automatically done in the instruments.

 

4) Well, you can use Forward to compute several points at various angles from SSW to WSW and hope your handheld accuracy is good enough.

 

The metal detector really would help here, I think.

 

Be sure that any place you are looking is 1.22 m (4 ft) NNE of a place that a witness post COULD have been placed.

 

5) With a manageable slope, the elevation change itself is a good clue. You could take a pole and place it at trial positions and have somebody tell you if the top was level with the old fort (sighting over a carpenter's level on a solid support would get close enough). At 20.01 feet, that's not so easy, but maybe you could do it in 8 ft +8 ft+4 ft stages to get down to the desired elevation and then sight several points at that elevation to define your search path.

 

To make sure you are on the right level, notice that it is 31 ft below FH0805.

 

I don't see much else on this data sheet to help.

Edited October 1, 2010 by Bill93

[+Holtie22]

I guess my questions are these:

 

1) When this mark was set in 1984, they listed a distance and general compass direction to the mark. Am I correct in assuming that "southwest" in the description is simply a general direction from the compass and not actually intended to mean 225 degrees?

 

2) They listed the distance as 108.20 meters. In my world, listing the last zero in that number means that it is a significant value and that it was measured to two decimal places of accuracy. I realize I'm splitting hairs at this distance and the difference between 108.1 and 108.3 is not huge, but was it really measured that accurately?

 

3) Because of the difference in altitude of the base of the flagpole and the location of the marker (6.10m according to the datasheet), how is that distance measured? Picturing a right triangle with the short leg going up from the mark, and the long leg going from a point in space above the mark to the base of the flagpole, what is being measured? Is the measurement for the long leg (the base) of the triangle or is it for they hypotenuse? I realize the difference is only ~0.2m, but I'm curious.

 

4) For marks like this with fairly sparse descriptions, is there an easier way than to trace out an arc at the correct distance and sweep with a metal detector (which I don't have). On a related note, is there an easier way to trace out that arc than with a tape measure? Because of the distance involved, the trees in the way, and the 6m elevation change, that's not the easiest thing to trace.

 

5) I'm still fairly new at this. Is there something in the datasheet that I've overlooked that would make this easier?

 

I hope those questions make sense. I'd welcome any input you good folks have on this.

1. You are correct

2. That's the way significant figures work in my world as well. And yes, they are quite capable of measuring the distance that accurately.

3. Unless otherwise specified, all surveyed distances are horizontal, ie. the short leg as opposed to the hypotenuse.

4&5. Swinging an arc over that large a distance is extremely difficult. You're better off trying something else first. In this particular case, (and frequently in many others), the easiest approach would be to examine the USGS Topo map of the area to see if the BM is depicted (it is) and then scale coordinates of the depicted location (N 35 23.314, W 094 25.989) to refine your search location. These coords appear to be about 500' north of the datasheet L/L, which is not that unusual for scaled locations, but I would be more inclined to rely on the topo map depiction than on the scaled datasheet coords.

It is unfortunate that the previous GC finders appear to have had more of a geocaching mentality, trying not to "spoil" future hunts by not giving more specific information about where they found it. In Benchmarking, the whole point is to make it easier for the next person to find the mark, providing something of a public service for those who need the mark for professional purposes.

 

Welcome to Benchmark hunting!

[+Harry Dolphin]

Hmmm... I would take into consideration the find logged by OzarkMthGhost, who said that the coords were about 50' off. (Though s/he didn't post any photos.) And 'remember the rock outcropping setting'. Looks like a wall along the top of the bluff? With a viewpoint? Old pole might have been there. New pole looks in a strange place. Topo maps show a BM to the northeast about 500 feet. That sounds too far off, and not listed in NGS. Keep us posted. (Hey! I'm the NPS junkie. I need to go there!)

[+dukeofurl01]

When you find it, make a waypoint in your GPS of the location, and post the coordinates with your find log.

[ArtMan]

It's frustrating when a previous log reported the mark found seven years ago, but left no additional clues. (I suspect, without really knowing or intending disrespect, that OzarkMtnGhost et al is a cacher, not a benchmarker.)

 

I can't add much to what the previous posters have said, but I would urge you to try to provide, if not a complete new description, then at least some more details, if possible -- or, at least, photos -- to help the next person find the mark.

 

ArtMan

[+secondgunman]

 

 

 

These three images are of the area around the benchmark. My pack is placed roughly where I expect to find it. All images are looking more-or-less to the north, with the river on the west and the uphill rise on the east. In the view to the NE, you can see a glimpse of the flagpole in the very center of the image. This gives you an idea of the terrain in the area. You can see that there isn't a witness post anywhere in the area, and wherever it was must be on fairly level, fairly open ground. The biggest problem is the dirt that is deposited on the bedrock. Because of the volume of dirt involved, I'm gonna have to get a metal detector. If I had a smaller search radius, I might be able to get away with simple probing.....but I don't think that's gonna happen.

 

Once I find this one, I'm going to treat it like I would any undocumented mark. I'll put up a log something like this.

Edited October 2, 2010 by secondgunman

[tosborn]

Be careful with respect to using the metal detector if the area in question is within the bounds of the National Historic site. The National Park Service prohibits the use of metal detectors and will likely confiscate it unless you get their prior approval.

Edited October 2, 2010 by tosborn

[mloser]

A couple of observations...

 

Be careful in thinking that the wooden flagpole is the metal pole in the description. I would think that if the metal pole was a flagpole it would have been described as such. Even if it was, assuming that it was replaced in exactly the same spot with a wooden one is not safe.

 

The spot where your backpack is seems to be sloped slightly, although that might be the dirt and not the outcrop. With all that flat rock around it wouldn't make sense to set a mark on sloped rock. Not that it would be out of the question but it wouldn't be the first place I headed. I would be more likely to head right to that large flat spot beside the river.

 

The other finder, who sadly included only the one "clue" about "remember the rock outcrop setting". Since the whole area seems to be a rock outcrop, either the clue is no help, or he thought one area was more "outcroppy" than others. He also doesn't mention it being under dirt. I would like to think that if it WAS buried he would have said as much and not just said it was fun. Like Artman, I usually take geocaching finds of benchmarks with a grain of salt, but he has 99 bench marks to his credit and showed enough sense to find reference marks for triangulation stations. Unlike benchmark hunters though he may not have wanted to provide spoilers in his recovery, hence the vague references to it being fun and to remember a rock outcrop.

 

Even though there is no witness post, the idea of a witness post can help. The mark is about 4 feet NNE of a witness post. That means that there had to be a place to stick a witness post south of the mark, which may mean that the mark is near the south edge of an outcrop, since there had to be dirt to put the witness post in.

[ArtMan]

. Like Artman, I usually take geocaching finds of benchmarks with a grain of salt, but he has 99 bench marks to his credit and showed enough sense to find reference marks for triangulation stations. Unlike benchmark hunters though he may not have wanted to provide spoilers in his recovery, hence the vague references to it being fun and to remember a rock outcrop.

Clarification for the record:

 

Though I think, as a rule, geocachers who stray over to the benchmark side tend to be less careful and accurate than those of us — like mloser — who are experienced and careful benchmarkers, that is not what I was referring to.

 

Rather, in my original post, I was trying to point out that the cultures of geocaching and benchmarking are fundamentally different.

 

In geocaching, the game is to find what someone has hidden, and not to provide help to those who come looking for the cache later.

 

In benchmarking, the goal is also to find something which may be hidden, but the original purpose of placing the mark and publishing its description was for it to be found and used later on, and when a mark is recovered and reported to the NGS or logged here on geocaching.com, the goal is to provide as much additional useful information as possible to assist the next recovery. Reminding someone to "Remember the rock outcrop setting" is the kind of clue or hint that a geocacher would employ, not a benchmarker (who would tell you how far in which direction from which outcrop).

 

Or, in other words: geocachers obfuscate; benchmarkers elucidate.

 

ArtMan

[kayakbird]

I'm guessing that in 1984 the standard WP was a metal placard on a steel post - T or U. Check all the cracks in the rock for the remains of one, or evidence where one had been. kayakbird

[Wintertime]

FWIW--and I realize that we're dealing with a scaled location--the aerial maps linked from the Geocaching.com page for this mark show it about 100 feet away from the river, up near the trees. Are there any prominent rock outcrops in that area, a bit further upslope than you've been looking?

 

Patty

[+secondgunman]

I'm about ready to give up on this one. I've searched the rock outcrop thoroughly from a spot about 50m south of where I expect the marker to be all the way north to where the outcroppings end and have pretty much come up blank. There are numerous spots along the bedrock where barges used to anchor to the shore, but those don't help us any.

 

 

 

I was walking with one of the Rangers from the park last week and he mentioned having seen a marker like the one I was describing. Turns out he did know where a marker was, and it's in the right area, but it's the wrong marker. He was able to direct me to a Corps of Engineers marker that is in very good condition. This marker is 54m SE of the area I've been checking lately.

 

 

While we were in the area, he looked down and said "there's this, but that's not what you want".......and I think he's right, but I'm not sure. I've never seen a benchmark that's missing the top before, so I suppose this could be it. It looks more like a railroad spike to me though. What are your thoughts? The spike is 118.8m SW of the flagpole in my original discussion at a bearing of 225 degrees.

 

 

I looked in the area around the spike and didn't see anything within a 2m radius that looks even remotely like a spot where a witness post might have gone. This makes me think that I'm way off base here.

 

Edited October 5, 2010 by secondgunman

[ArtMan]

About how big is that RR spike-looking object?

 

Most disks I've seen are set on a round rod. I don't think I've ever seen a square one.

 

ArtMan

[+_dxd_]

well, here's my worthless contribution to the discussion

 

"SATELLITE: THE SITE LOCATION WAS REPORTED AS NOT SUITABLE FOR

SATELLITE OBSERVATIONS - November 01, 1989"

 

Does that mean it is probably under the trees ? Or is that used any time there might be trees somewhere near-by within a certain distance?

 

keeping in mind of course that was 21 years ago, trees could have been removed...

[+secondgunman]

About how big is that RR spike-looking object?

 

I didn't think to measure it while I was there. I'll give you an exact number tomorrow morning, but the round top was a little over an inch with the square rod being a little under an inch.

 

I forgot to add earlier. This spike is just a few feet from where I was focusing my efforts all last week. The bush in this photo is the same one you can see in my third photo from the orginal post.

 

[+Rotareneg]

If you're certain that's the right area, you might try the area under and around that little tree because, as dixiedawn pointed out, it's marked as not suitable for satellite observation.

[Bill93]

The geocaching Found log may have resulted from sighting of the Corps disk and tell you nothing about the one you seek. The people who logged it in 2003 probably had very little experience in identifying disks. It was logged 8 days after their first benchmark.

 

Is there a river gage station not too far away listed on the Corps web site? Maybe you could use the current river elevation (if there are no locks or falls between) as a rough guide to how high you should be looking.

[Wintertime]

I forgot to add earlier. This spike is just a few feet from where I was focusing my efforts all last week. The bush in this photo is the same one you can see in my third photo from the orginal post.

"secondgunman," did you see my question about whether you checked for any rock outcroppings uphill a bit, farther away from the river?

 

Patty

[mloser]

I keep going back to Holtie's mention of the topo map and the bench mark indicated on it. Like him I come up with a distance of 500 feet north of the location you have been searching. And in looking at Google Earth I just MIGHT also see a large metal pole, although it could just be one of the many power poles in the area--the shadow is just indistinct enough to convince me that there are no crossarms on the top to carry wires. But it could just be a product of the angle of the photograph. It also seems to be a bit far from the mark but it IS in the right direction and IS a big ol' pole!

You might consider heading to Holtie's adjusted coords and see what is there.

[holograph]

I vote woth Holtie and MLoser. It is possible that the direction was incorrectly stated as southwest of the pole when instead it should be northwest.

 

The two images below provide a strong argument. The first image shows a radius of 108.2 meters around a pole on the grounds of the old fort. The second image shows the USGS quad superimposed and georegistered to the same image. The BM on the USGS quad, at elevation 408 feet, lies almost directly on the 108.2 meter radius of the pole, and the datasheet states that the elevation of FH0806 is 407.5 feet.

 

 

[ArtMan]

Not helpful in this case, apparently, but the city of Fort Smith has a GIS map that shows survey monuments with linked datasheets.

 

This mark isn't in their database, unfortunately. I only mention it as a reminder that municipalities and counties increasingly have interactive GIS applications on their websites, and local datasheets I've seen sometimes have maps or other finding aids that do not appear on NGS datasheets.

 

ArtMan

[+secondgunman]

Thanks to everyone for posting their comments and suggestions. I may not have responded to each of them individually, but I promise I've read them all and have considered them all.

 

I spent another hour or so at the historic site today, this time focusing on the area NW of the flagpole. This is the area where Holograph, Holtie, and MLoser have suggested looking. I had made a cursory search of the area earlier, but I gave it a fairly thorough search today. The entire area is dirt and grass with moderate to heavy tree cover. This means that my GPSr is less than totally reliable. It also means that if the mark is still there, it is most likely covered with dirt and grass. The highlight of the morning came when I remembered seeing a green metal post near a tree. The tree is surrounded by chicken wire, so I initially assumed that the post was there to hold up the wire. The tree and post are about 100 feet SSW of the point where I was focusing my search, but I thought I'd give it a try. Karrie Powers, one of the Park Rangers in the maintenance division has been very helpful in my search and she offered to join me with a gas-powered weed eater to make it easier to access the area around the tree. As we were setting up, another Ranger (Greg?) came to join us. It turns out he's the guy who placed the post there, it's been there since roughly 2002, and he put it there to hold up the chicken wire. False alarm. It looks like IF the marker is in this area then it's going to require a metal detector to find it.

 

In talking with Karrie and Greg, neither of them are familiar with any large posts, metal or otherwise, in the area of the old fort. I've walked the area from the flagpole at the center of holographs images north all the way to Garrison Ave and south as far as is reasonable before leaving the National Park grounds and I'm comfortable saying that the flagpole is the only large pole around. There's a power line tower to the north, but it's a huge metal structure with four legs forming a square approximately 20 feet on a side. I don't think that's what the description mentions......plus, it's way too far to the north.

 

Wintertime: Yeah, I saw your suggestion. In this area, you're basically looking at rock outcroppings at water level. As you move to the east, the rock outcrops move up in steps ranging from a few inches up to a foot or two at a time. Once you reach a distance from the river, the rock is covered with dirt and the ground starts to slope up in a slope instead of in steps. Once the dirt starts, the rock is gone. There is no rock outcrop from the dirt once you get past 10 or 15 feet from the river.

 

Bill93: I don't want to say anything bad about anyone else, but that's kinda what I'm thinking too. I had noticed that this was one of their earlier benchmark finds and because of that was taking their recovery log with some skepticism.

 

ArtMan: The RR-spike thing is almost exactly 1/2 inch across on the shaft and 1 inch diameter on top. Also, thanks for pointing out the Fort Smith GIS map. I wasn't aware that it was online.

 

For the moment, I'm going to give up on this one. I have a job interview tomorrow and am going to spend the rest of the day listening to some postseason baseball and doing my pre-interview homework. Hopefully I'll get this job and will be moving away from here very soon. I hate to put this much time in and come up empty, but sometimes it happens. I'll log a DNF on geocaching.com and hope that somebody else can pick up where I've left off.

 

Thanks for all the input! If this interview doesn't go well, I'll go buy a metal detector and head back out in a week or so.

[holograph]

It sounds like you've searched heroically. It was possible (although not likely, given the number of prior recoveries) that the "southwest" direction was mis-stated, but the one certain thing is the rock outcrop. If the only rock outcrop is in the location you originally searched, it seems likely that the mark is lost or very well hidden.