Can Not Locate Any Benchmarks

[+Milbank]

I did a search for benchmarks in my area and found a couple that look like they should be there.

 

The ones I have looked for are all just a couple miles out of town.

 

The ones I have tried to find all say this:

 

Marker Type: survey disk

Setting: set into the top of a round concrete monument

Stability: May hold, but of type commonly subject to surface motion.

 

Being of concrete I thought it would be easy to find.

When I get out in the area the GPS point to the ditch off the side of the road were the grass is 3 ft high.

 

Does that sound right?

Sould I be looking in the high grass in the ditch or are they located more up towards the edge of the road?

 

So far it's not been as easy to find them as I thought.

I have looked for three different ones and did not find any of them.

 

There are some listed in my town too, but I thought there would be less people around if I looked for the ones out of town.

[+GeckoGeek]

Being of concrete I thought it would be easy to find.

.

Maybe.

 

When I get out in the area the GPS point to the ditch off the side of the road were the grass is 3 ft high

 

Maybe. Is the LOCATION for the marks you are searching for SCALED or ADJUSTED? If it's ADJUSTED, your GPS should take you right to the mark - or at least withing the unit's accuraccy. 10ft isn't all that unusual.

 

If the mark is SCALED, then it could be 200-600 feet away. In that case you must read the description.

 

Even once you're in the right area, things do change. The mark may be under leaves or hidden in grass and whatnot.

[2oldfarts (the rockhounders)]

For the first couple of benchmarks you try to find, I would suggest that you look for some that have been found by another cacher. This way you know the mark has a high probability of being there. It will give you a feel for what it takes to locate benchmarks.

 

Good luck,

 

John

[+Colorado Papa]

I suggest you start with some easy ones like AE9743 and AE9740 which are scaled but recently mounted. Follow the description, find the mark then read your GPSr and compare the reading with the published coordinates.

 

I use the term "recently" refering to since 1990 as compared QQ0099 which was mounted in 1905. Interesting NOT FOUND/FOUND reports about that one.

 

The best way to find a mark is to go by the description, no matter if adjusted or scaled. Many finders on here claim adjusted is accurate to within a few feet but my experience is that they, too, can be off by more than 100 feet. Blame it on the GPS? I don't think so when the EPE is 14 feet.

[+GeckoGeek]

Many finders on here claim adjusted is accurate to within a few feet but my experience is that they, too, can be off by more than 100 feet. Blame it on the GPS? I don't think so when the EPE is 14 feet.

Do you have an example? Given that adjusted marks are supposed to be accurate to within inches, that large an error would indicate a problem.

 

Keep in mind that EPE is the GPS's guess as to how accurate it is. I don't claim to know all the details, but I wouldn't be supprised but what that could be in error due to reflections of the signal off of nearby objects.

[+Milbank]

Colorado Papa,

 

Thanks for posting them with the links.

I will see if I can find them first.

 

Thanks again,

[+Colorado Papa]

Do you have an example?

Not off hand. Am not about to go back through 140+ logs.

I'll watch for one next time.

[2oldfarts (the rockhounders)]

Milbank - a good way to check your GPSr for accuracy is to goto an adjusted benchmark! Set your GPSr on the disk and let it sit for about 20 seconds and take a reading. It will be within 10 feet of the given coordinates. Usually we have our unit reading less than 5 FT.

 

If you try for an adjusted benchmark and your unit takes you to a spot where there is no disk then double check it using the "Official History" on the benchmark page. If the mark is not there, then it is time to look for some indication that the benchmark has been destroyed or buried.

 

Adjusted readings are usually in the XX.XXXXX' range. That's 5 decimal places on the minutes reading. That's definitely more accurate than our units will read!

 

Good hunting,

 

John

[+GeckoGeek]

Not off hand. Am not about to go back through 140+ logs.

I'll watch for one next time.

Thanks. Just so you understand my position, I'm not saying you didn't experence what you experenced, but unless the datasheet is wrong due to a typo during data entry, I'd suspect a GPS error.

 

GPS should be good for adjusted marks, but it always pays to read and follow the description as well.

[Z15]

FYI

 

Adjusted data is not typed onto the data-sheets. Its a direct output of a least squares adjustment program.

Edited June 7, 2004 by elcamino

[+GeckoGeek]

FYI

 

Adjusted data is not typed onto the data-sheets. Its a direct output of a least squares adjustment program.

Somewhere along the line the data got typed - like from the orginal paper datasheets. Is it possible for an error there to create this problem?

[+Tacguy]

Well, given your location, there are a few easy finds like thie church (which tend to still be standing:

 

CONGREGATIONAL CHURCH OF MILBANK Spire

 

and maybe this RR Tank:

 

FINIAL OF BLACK WATER TANK OF C.M. ST. P AND P RR, LOCATED AT ITS ROUNDHOUSE

 

But some you just need to wade in there and start searching around. Look for descriptions that say "Witness Post" which is an object near a benchmark that marks the Bench. Or find some that say the Bench is mounted in a sidewalk or on a bridge, these are easy finds in an area that is open to everyone.

 

Where you are at alot of Benches may be in historic buildings drilled into the cornerstones. Those are easy. Some are in flagpole bases too.

 

Check this one out and ask the building manager about the strange benchmark that is under a mat of the door entrance!

 

AT THE NORTH ENTRANCE TO THE MASONIC BUILDING

 

heck, if I had all those things around I wouldn't have to travel. I am in L.A. where all the benches are under pipe caps in the middle of highways!

[+HikingMan]

My third benchmark search actually led to one. The first two sought were long gone. This third one's coordinates led to a new building, but the actual benchmark is still there - about 50 feet away. The description helped get through the dilemma and find the actual location.